First CPPA PIs Meeting Abstract

This page presents the abstracts for the posters given 14-15 August 2006 at the First (CPPA) PIs Meeting at the Hilton El Conquistador Resort in Tucson, AZ

Radar-observed precipitation during NAME 2004

David A. Ahijevych

National Center for Atmospheric Research

ahijevyc@ucar.edu

Co-Authors:

Richard E. Carbone, National Center for Atmospheric Research

Timothy J. Lang, Stephen W. Nesbitt, Steven A. Rutledge, Colorado State University

This work showcases version 2 of the NAME radar network composites, which is available for download by the larger hydrologic and climate community at http://data.eol.ucar.edu/master_list/?project=NAME. This version features more accurate rain rate estimates and a better interpolation scheme than version 1. The rainfall rate estimates use the lowest unblocked radar beam at each grid point and incorporate various bias corrections. Composite fields include reflectivity, rainfall rate, height above sea level, and satellite IR brightness temperature, and are available every 15 minutes on 0.05 and 0.02 degree latitude-longitude grids.

This poster will describe the primary rainfall modes observed by the radar network during NAME from 8 July to 22 August 2004. These are featured in a reduced-dimension framework with one principal axis parallel to the Sierra Madre Occidental and other perpendicular. Total rainfall will also be stratified by time of the diurnal cycle and regime type. In the usual diurnal cycle, rainfall initiates over the higher terrain and progresses toward the coast during the evening hours. In disturbed conditions, the convection continues well out to sea and persists until morning. These periods are also exhibit more propagating convection, which is shown to be correlated to periods of enhanced low-level wind shear. Contrary to an early hypothesis, our cursory evaluation of NCAR/NCEP reanalyses shows little correlation between the position of easterly waves and the observed radarrainfall regime.

HYDRAULIC REDISTRIBUTION BY PLANT ROOTS: A Mechanism of Interaction between the Biosphere Moisture Reservoirs of the Deep Soil, the Near-surface Soil, and the Lower Atmosphere

Geremew G. Amenu and Praveen Kumar

Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801

amenu@uiuc.edu, kumar1@uiuc.edu

It is well known that, next to the ocean, the terrestrial component of the climate system has a memory that may control the long-term (seasonal to annual) predictability of a climate. Further, recent studies have documented that the deeper layer of the soil has longer memory than the near-surface. The underlying hypothesis of this study is that .the hydrologically active depth of rooting zone in current climate models is underestimated and that the longmemory deep soil-layer may have significant impact on land-atmosphere interaction in vegetated environments.. Available observations of rooting depth around the globe suggest that vegetations in water-limited ecosystems have far deeper rooting than what current modeling approaches assume. Moreover, it has been well documented that plants in water-limited ecosystems use a mechanism called .hydraulic redistribution (HR)., where moisture moves via the root system from moist soil layers to dry soil layers. We model the HR, and investigate its effect and that of the rooting depth on fluxes at the land-atmosphere interface in water-limited ecosystems. HR is modeled by assuming the plant root system as a conduit for moisture transport from wet soil reservoirs to dry soil reservoirs, while at the same time conveying moisture to fulfill the transpiration demand at the canopy. Our analyses suggest that rooting depth coupled with HR could be a main mechanism for facilitating the interaction between (i) the long-memory deep soil and the medium-memory near-surface soil, hence, enhancing the influence of the near-surface soil on the near-surface atmosphere and (ii) the long-memory deep soil layer and the short-memory atmosphere, and hence the role the deeplayer plays. These mechanisms have critical implications in long-term climate and ecological predictions, and may demand re-evaluation of modeling approaches of water uptake by plant roots.

Improving Water Demand Forecasting in the Middle Rio Grande River Basin

Kristi Arsenault

Evapotranspiration (ET) from irrigated crops and riparian vegetation, and evaporation from open-water surfaces are the primary consumers of surface water in the Western U.S.. To quantify these water requirements, the U.S. Bureau of Reclamation (Reclamation) has developed and implemented the Agricultural WAter Resources Decision Support (AWARDS) system, which is an automated information system to assist water managers and users by providing easy access to rainfall and daily crop water use estimates. Building on the AWARDS decision support tool (DST), Reclamation has developed the Evapotranspiration Toolbox (ET Toolbox) which adds land cover/use information within selected Hydrologic Rainfall Analysis Project (HRAP) grid cells when estimating daily surface water use. Currently, the AWARDS ET Toolbox utilizes NCEP Eta 12km meteorological forecasts, ad Doppler Radar products as input forcings, and a modified Penman equation and derived crop coefficients (Kc) to estimate ET for the different land cover types.

To help further investigate the use and potential benefits of different land surface models (LSMs) and remote sensing datasets in estimating ET and water consumption, a team at NASA Goddard Space Flight Center is customizing the Land Information System (LIS) modeling environment for comparison and validation studies with the AWARDS ET Toolbox DST in the Middle Rio Grande River Basin area. The AWARDS ET Toolbox land cover classification dataset and meteorological forcing datasets have been implemented in LIS. This will allow for a thorough comparison study between the different LIS LSM (i.e., Noah 2.7, CLM2, and Mosaic) ET-based algorithms and the AWARDS DST.s current operational setup. Also in this comparison study, the LSMs and AWARDS ET Toolbox will be validated against in-situ eddy covariance flux and other meteorological tower data for various vegetated areas (i.e., riparian, agricultural). All models and algorithms will be forced using local meteorological data, but some additional experiments will be made using the Eta 12 km and North American Land Data Assimilation forcing datasets. Finally, some Terra and Aqua MODIS remote sensing products (e.g., leaf area index, land surface temperature) have been developed further for use and assimilation in some of the LIS LSMs, to evaluate the usefulness of NASA.s satellite derived products within the AWARDS decision support tool.

Numerical Simulations of Recent Warm-Season Weather: Impacts of a Dynamic Vegetation Parameterization

Adriana Beltrán-Przekurat

Adriana Beltrán-Przekurat¹, Curtis H. Marshall² Roger A. Pielke, Sr.¹

¹Department of Atmospheric and Oceanic Sciences, University of Colorado, CIRES, Boulder, CO.

²Board on Atmospheric Sciences and Climate. National Academy of Sciences. Washington, DC.

The impact of dynamic vegetation on ensemble dynamical reforecasts of recent warm-season weather over the continental United States was assessed using the Regional Atmospheric Modeling System (RAMS) and a fully coupled dynamic vegetation version of RAMS, the General Energy and Mass Transfer. RAMS (GEMRAMS). Two 10-member ensembles were produced for the June- August periods of both 2000 and 2001. For each period, one of the members used the standard RAMS, and the other the GEMRAMS version. Initial and lateral boundary conditions for the regional model domain for each June-August period were provided by a 10-member global ensemble reforecast produced with the NCEP Seasonal Forecast Model (SFM), which was the operational global dynamical forecast system in use by the Climate Prediction Center during 2000- 2001. For each period, a pair of .baseline. simulations (not forecasts), one with GEMRAMS and one with RAMS, were created using the NCEP Reanalysis as initial and lateral boundary conditions. In this experimental design, the impact of dynamic vegetation in ensemble forecasts on a regional domain can be assessed against the use of dynamic vegetation in a simulation, produced with a "perfect" global forecast (i.e., Reanalysis).

Precipitation in the regional ensembles was largely controlled by the driving large scale forcing (i.e., the SFM boundary conditions). A large precipitation bias exists over the regional domain in the SFM itself that it is amplified in the RAMS and GEMRAMS simulations. The areas with the largest spread of the ensemble members tended to coincide with the areas with the largest biases. For the time periods and model set-up considered in this work, under an explicitly predictive model configuration the use of a more complex parameterization of land surface processes with dynamic vegetation added little value to the skill of the seasonal forecast over the regional domain.

Ensemble Reforecasts of Recent Warm-Season Weather: Impacts of a Dynamic Vegetation Parameterization.

Adriana Beltrá Przekurat¹, Curtis H. Marshall² Roger A. Pielke, Sr.¹

¹ Department of Atmospheric and Oceanic Sciences, University of Colorado, CIRES, Boulder, CO.

² Board on Atmospheric Sciences and Climate. National Academy of Sciences. Washington, DC.

An EPIC 2001 ITCZ integrated dataset and cloud-resolving model

Chris Bretherton

We will report on progress toward an EPIC 2001 ITCZ integrated dataset and cloud-resolving model simulation. Both cover a roughly 200x200 km region centered on 10^oN 95^oW for the period 12-30 Sept. 2001. The integrated dataset includes measurements taken from the Ron Brown

contributed by several EPIC PIs and distilled to time-height series at hourly or longer resolution. These include sondes, area-averaged rainfall derived with C-band radar, reflectivity histograms from C-band and cloud radars, surface fluxes and meteorology, satellite-derived cloud-top pressure/optical thickness histograms and top-of-atmosphere radiative fluxes and ERA40 reanalysis-based estimates of rainfall, mean vertical air motion and horizontal moisture and temperature advection. These datasets are being incorporated into a web site and compared with simulations of the period with the CSU SAM6.4 cloud resolving model over a doubly-periodic domain forced by the ECMWF advective forcings and observed SST with winds nudged to the sonde observations. Future plans for expanding and applying the dataset will also be discussed.

Hydrologic variations in the Gulf of California Watershed in the context of climate change: Investigations of the recurrence of extraordinary events and their possible consequences

Luis Brito-Castillo

The information concerning climate change in several regions of the world is quite large, but in Mexico the studies dealing with this kind of investigations are scarce. The air surface temperature has been the variable that best fitted the predictions, because of its rapid response to greenhouse effect. The studies examining minimum air surface temperatures revealed that, in Sonora, a warm trend is observed to the west, but cold trend to the east. These results imply the necessity to investigate the ecological response to regional climatic perturbations such as the extreme hydrometeorological events: heavy or scarce rainfalls, flash floods, extremely high and low temperatures, etc. In Mexico, the lack of detailed studies focusing on the effects and the causes of such events over the ecosystems has motivated the preparation of this proposal; our contribution is to try to document the regional climate change and its ecological consequences, such as the migration or invasion of species, and extinction and/or severe damage to their habitats. For this research, the Gulf of California watershed (GCW) has been chosen as the zone of study, from the Sonoyta river basin in the north to the San Pedro river basin in the south, and the Pinacate and Gran Desierto de Altar biosphere reserve (the reserve), as a specific case study, due to its high ecological value, where the endemic or with some degree of taxonomic differentiation, flora and fauna, or with some category of protection, represent one of the most important biological and taxonomic values. For methodological reasons, the study is aim to focus from the generality (the GCW) to the specificity (the reserve), taking up our previous investigations in the GCW where we reported rainfall and streamflow reconstruction; the 700 mb atmospheric flow patterns related to moisture transportation toward hydrologic basins; and the ENSO modulation effect and the modulating influence by the tropics and adjoining waters. Also, because it results easier to first understand the climatic effects of global and synoptic scales and then focusing on a specific region, the reserve, where most of the information necessary to understand the climate changes results insufficient. This is the reason to maintain using dendrochronological techniques to reconstruct the current available information in the reserve, and to take field samples to understand the changes in plant structure and/or reductions in the genetic homogeneity of the species, to support more global analysis results. To accomplish these goals a data base of the entire zone of study will be created, that includes climatic variables (rainfall, air surface temperatures, streamflow), maps (vector data files) and plant species (samplings and reference works at museums); and by searching correlative mechanisms with different indices of climate variability which help understand the origin of the changes. This project try to give answer to questions such as: Extreme climate events in the zone of study are part of the natural climate variability or are a consequence of the climate change process in the same sense as it has been reported in other regions? Are we prepared to face the consequences of these changes? What kind of actions will be necessary to be done to attenuate the negative effects of these changes in protected areas, such as the reserve?.

The Marine Atmospheric Boundary Layer over the Eastern Pacific and its Simulation in Climate Models

Michael A. Brunke

The atmospheric boundary layer (ABL) height (h) is an essential parameter in weather and climate models. An analysis of almost 1000 soundings from 11 cruises between 1995 and 2001 in the eastern Pacific reveals large meridional, zonal, seasonal, and interannual variations in h. When compared with h produced by a couple of climate models (NCAR's CCSM and NCEP's Climate Forecasting System or CFS), the boundary layer height parameterization is shown to need improvement particularly in certain regions of the eastern Pacific. CCSM's h is generally underestimated especially north of 20°N in August and September, and CFS's h is overestimated in the same region. Directly applying the radiosonde data to these models' formulations for the determination of h at their respective vertical resolutions reveals that the CCSM formulation significantly underestimates h and that the CFS formulation almost always overestimates h. A simple adjustment of h to cloud top or bottom based upon cloud thickness is shown to improve CCSM's determination of h. When this adjustment of h to cloud top or bottom is implemented into the atmospheric component of the CCSM coupled to the land component, the simulated stratus and stratocumulus clouds are significantly changed. At the Conference, we will show how the model simulation of other parameters are changed by this adjustment as well.

We have also analyzed field experimental data over the eastern Pacific as well as other oceanic regions to document the probability distribution functions of cloud base, top, thickness, and cloud liquid water path (LWP). The relationship of stratus/stratocumulus cloud fraction and depth with LWP has also been established. We will discuss these results in our presentation.

Investigation of the Summer Climate of North America: A Study with the Regional Atmospheric Modeling System

Christopher L. Castro

53 years of the NCEP-NCAR Reanalysis are downscaled using the Regional Atmospheric Modeling System to generate a regional climate model (RCM) climatology of the contiguous U.S. and Mexico. The simulations capture the climatological transitions in precipitation and temperature associated with the North American monsoon, though model generated precipitation is overestimated. The time varying modes of convection are well represented, particularly the diurnal cycle. Interannual variability in the simulations is evaluated with respect to the dominant modes of Pacific SST variability. Timeevolving teleconnections accelerate or delay monsoon evolution. The most significant response in RAMS-generated fields occurs simultaneously with the time of maximum teleconnectivity in July. At this time, there is an opposite relationship between precipitation in the core monsoon region and the central U.S. The teleconnections affect low-level moisture transport and the timevarying modes of convection. Recent tropical SST warming is associated with a general increase in rainfall over most of North America, except in western Mexico. The long term trend in Mexican monsoon rainfall is due to a decrease in moisture transport from the East Pacific. (Poster in English and Spanish)

Statistical Characterization of the Spatiotemporal Variability of Soil

Christopher L. Castro

Previous work has established that the dominant modes of Pacific SSTs influence the summer climate of North America through large-scale forcing, and this effect is most pronounced during the early part of the season. It is hypothesized, then, that the land surface influences may become more dominant in the latter part of the season as remote teleconnection influences diminish. As a first step toward investigation of this hypothesis in a regional climate model (RCM) framework, the statistically significant spatiotemporal patterns in North American precipitation (specified by the standardized precipitation index, or SPI), soil moisture, and vegetation are determined. To specify these respective data we use: CPC gauge-derived precipitation (1950-2000), Variable Infiltration Capacity (VIC) Model NLDAS soil moisture (1950-2000), and satellite-derived (GIMMS) NDVI (1981-2002). The principal statistical tool used is multiple taper frequency domain, singular value decomposition (MTM-SVD), and this is supplemented by wavelet analysis for specific areas of interest. The significant interannual variability in all of these data occur at a timescale of about 7 to 9 years and appears to be the integrated effect of remote SST forcing from the Pacific. Considering the entire year, the spatial pattern for precipitation resembles the typical ENSO winter signature. If the summer season is considered separately, the out of phase relationship between precipitation in the central U.S. and core monsoon region is apparent. The largest soil moisture anomalies occur in the central U.S., since precipitation in this region has a consistent relationship to Pacific SSTs for the entire year. This helps to explain the approximately 20 year periodicity of drought conditions there. Unlike soil moisture, the largest anomalies in vegetation occur in the southeast U.S. and appear less related to rainfall. In the core monsoon region, interannual variation in vegetation growth is governed by monsoon precipitation. Future RCM work will use these patterns of long-term variability of soil moisture and vegetation in sensitivity experiments investigating land-surface interactions in the warm season.

Global Model Investigation of Warm Season Precipitation for North American Monsoon Experiment

Craig Collier

Guang J. Zhang and J. Craig Collier

Scripps Institution of Oceanography

The simulation of the North American monsoon by the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3) and by the Community Atmosphere Model (CAM3) and sensitivity to model resolution and parameterization of convection is evaluated. This study makes use of hourly gauge-based rainfall data, satellite-based rainfall measurements from the Tropical Rainfall Measuring Mission (TRMM), gauge-based rainfall data from the North American Monsoon Experiment Enhanced Rain Gauge Network (NERN), and the NCEP-NCAR reanalysis. During the North American monsoon season, precipitation is significantly undersimulated in the NCAR model over the southwestern U.S. Significant biases exist in regional monsoonal evolution, the diurnal cycle of rainfall, and the vertical transport of moisture through convection. When the resolution of the model is increased from T42 to T85 to afford more realistic representation of the Gulf of California and the Sierra Madre Occidental mountains, the only significant improvement realized is in the simulated distribution of precipitation over western Mexico. Only minimal improvement in monsoonal evolution is evidenced over the U.S. southern Great Plains, in association with an anomalously large region of enhanced mid-tropospheric descent.

Upon use of an improved Zhang-McFarlane parameterization for deep convection, the negative precipitation intensity bias over Arizona and New Mexico is significantly reduced or eliminated in some places. Additionally, in certain core monsoon regions, simulated monsoon evolution agrees more closely with the observations. The modified convection scheme improves the diurnal cycle of rainfall over extreme northern Mexico, southern Arizona, and most of New Mexico as well as the upper-tropospheric water vapor distribution. However, use of the modified convection scheme results in significantly increased biases in the diurnal cycle of rainfall over a large region of northwestern Mexico, a result identified over the southeastern and northeastern U.S. as well. These biases are due to biases in the simulation of extremely long rainfall events, likely associated with systematic synoptic weather disturbances. A commonality among the regions with most deficiently simulated diurnal cycles is the observed relationship between CAPE and precipitation. For regions of the eastern U.S. and northwestern Mexico, diurnal variations of CAPE and precipitation are approximately in phase with each other, and in these regions the new scheme fails to capture the diurnal cycle accurately. Therefore, the sensitivity of the simulation of warm-season precipitation to the model.s convection scheme is itself sensitive to the local convective regime.

Application of NARR-Based NLDAS Ensemble Simulations to Continental-Scale Drought Monitoring

Brian Cosgrove

SAIC / NASA GSFC

Brian.Cosgrove@gsfc.nasa.gov

Charles Alonge

SAIC / NASA GSFC

calonge@hsb.gsfc.nasa.gov

Government estimates indicate that droughts cause billions of dollars of damage to agricultural interests each year. More effective identification of droughts would directly benefit decision makers, and would allow for the more efficient allocation of resources that might mitigate the event. Land data assimilation systems, with their high quality representations of soil moisture, present an ideal platform for drought monitoring, and offer many advantages over traditional modeling systems. The recently released North American Regional Reanalysis (NARR) covers the NLDAS domain and provides all fields necessary to force the NLDAS for 27 years. This presents an ideal opportunity to combine NARR and NLDAS resources into an effective real-time drought monitor. Toward this end, our project seeks to validate and explore the NARR- suitability as a base for drought monitoring applications both in terms of data set length and accuracy.

Along the same lines, the project will examine the impact of the use of different (longer) LDAS model climatologies on drought monitoring, and will explore the advantages of ensemble simulations versus single model simulations in drought monitoring activities. We also plan to produce a NARR- and observation-based high quality 27 year, 1/8th degree, 3-hourly, land surface and meteorological forcing data sets. An investigation of the best way to force an LDAS-type system will also be made, with traditional NLDAS and NLDASE forcing options explored.

Over the next three years, the task list to accomplish these project goals includes: 1) Construct and validate 1/8th degree forcing data set based on NARR and observed precipitation and radiation, transferring to NOAA NCEP and research community when complete, 2) Investigate optimal forcing Global Model Investigation of Warm Season Precipitation for North American Monsoon Experiment

Relationships between Tropical Cyclones and Rainfall in Baja California, Mexico

M.A. Cosío and L.M. Farfán

CICESE, Unidad La Paz, Mexico

mcosio@cicese.mx

The influence of tropical cyclones in rainfall patterns over the Baja California peninsula is discussed. The impact of systems over the southern portion of the peninsula is analyzed and the study period is limited to the July- September) 2004.

We use the best-track dataset from the U.S. National Hurricane Center classify, based on distance from the circulation center, systems that approached the peninsula at several ranges. Data from the upper-air station at La Paz to evaluate humidity changes during the storm approach and rain-gauge from Mexican government are used to determine the spatial distribution precipitation. Our analysis shows that the season of 2004 resulted in below normal precipitation, when compared with the base period 1991-2004, over southern peninsula while above normal conditions occurred in the central peninsula.

Sensitivity of Warm Season Precipitation and a 2004 Gulf Surge Event to Variability in SST Forcing in the RAMS Model

William Cotton

The Colorado State University - Regional Atmospheric Modeling System (CSU-RAMS) is being used to examine the variability in monsoon-related warm season precipitation over Mexico and the United States due to variability in SST datasets. Given recent improvements and increased resolution in satellite derived SSTs it is pertinent to examine the sensitivity of the RAMS model to the variety of SST data sources that are available. If model response is large due to variations in ocean surface forcing we need to determine the most reliable datasets for use with RAMS when trying to improve predictions and simulations of warm season precipitation along the west coast of Mexico and the southwest U.S. In particular, we are examining this dependence across continental scales over the full warm season, as well as across the regional scale centered around the Gulf of California on time scales of individual surge events. As continental and regional scale simulations become possible at higher resolution, the use of higher resolution SSTs for surface forcing becomes a logical step in progressing towards improving warm season precipitation predictions. Results of these sensitivity studies will be presented and will highlight the sensitivity of the July 13-15, 2004 surge event to variable SSTs.

Horizontal and vertical structure of easterly waves in the Pacific ITCZ

Yolande L. Serra

University of Arizona, Tucson, AZ

serra@atmo.arizona.edu

George N. Kiladis

NOAA Physical Sciences Division, Boulder, CO

George.Kiladis@noaa.gov

Meghan F. Cronin

NOAA Pacific Marine Environmental Laboratory, Seattle, WA

Meghan.F.Cronin@noaa.gov

Abstract

Outgoing longwave radiation (OLR) and low-level wind fields in the Atlantic and Pacific intertropical convergence zone (ITCZ) are dominated by variability on synoptic time scales primarily associated with convectively coupled easterly waves during boreal summer and fall. A subset of the low pressure centers within such waves also spin up hurricanes, giving easterly waves additional significance for the climate in the Pan American region. This study uses spectral filtering on observed OLR data to capture the convective variability coupled to east Pacific easterly waves. The filtered OLR data are then used to isolate the horizontal and vertical structure in wind, temperature, and humidity associated with these waves through regression. Kinematic and thermodynamic fields for June-November 1979-2002 are provided by the National Center for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis project. Data from the Tropical Atmosphere-Ocean (TAO)/Triangle Trans-Ocean Buoy Network (TRITON) and the TAO/East Pacific Investigation of Climate (EPIC) arrays, along with radiosonde data are analyzed and compared with the NCEP/NCAR surface and pressure level analyses.

At the TAO buoys within the Pacific ITCZ, 3-6 day variability dominates the total sub-seasonal variability in surface meridional winds, temperature, and humidity. Pacific easterly wave dynamic structures have wavelengths of ~3300-5500 km and phase speeds of ~9-13 m s-1. In the surface observations the minimum in OLR occurs just to the west of the southerly maximum in both the far eastern portion of the basin near 95°W and in the central portion of the basin near 165°E. The 850 hPa reanalyses indicate similar results for 95°W, but indicate the minimum in OLR occurs within the southerlies at 170°E, shifted 1/4 wavelength from the surface observations. Our results suggest that these waves draw some of their energy from seasonal mean easterly .jet. regions across the Pacific present in the boreal summer/fall. More important to maintaining these waves, however, is the observed latent heating from the convection tightly coupled to the waves across the basin, and especially in the central Pacific.

The effect of shallow cumulus convection in a coupled regional model

Simon de Szoeke

Shallow cumulus convection evaporates stratocumulus clouds in the atmospheric boundary layer. The effect of shallow convection on the large-scale climate of the eastern tropical Pacific is investigated with a coupled oceanatmosphere model by disabling the shallow convection parameterization (noSC). Without shallow convection, the stratiform cloud fraction increases and surface solar radiation decreases. The sea surface temperature (SST) cools on average by 2 C. The cooling in noSC is larger under the low cloud deck south of the equator than north of the equator, resulting in an increase in the climatic meridional asymmetry. In the control run an ITCZ forms south of the equator in March-April. In noSC the SST is at most 24 C south of the equator and an ITCZ does not form. The perennial northern-hemisphere ITCZ in noSC is accompanied by year-round southerlies of at least ~3 m/s on the equator, considerably reducing the seasonal cycle of equatorial SST.

Moisture Sources and Transient Features Affecting the NAME Domain and Exploring a Dipole in Caribbean and Pacific Heat Storage That May Modulate TC Activity and Intraseasonal Rainfall Variability in the NAM

Art Douglas and Phil Englehart

Creighton University

The first portion of the poster summarizes our recent research on moisture sources and rain bearing transient features in the NAM domain. A 30-year climatology of surface moisture surge/seepage events at Douglas, AZ indicates that enhanced monsoon activity in southeast Arizona is directly tied to increased frequency of hourly moisture transport from the Gulf of Mexico. Gulf of Mexico moisture surges in far Southeast Arizona were three times more common than surges from the Gulf of California and the former account for approximately 65% of the summer rainfall at Douglas. Surges originating in the Gulf of California were far less effective in the enhancement of surface moisture and rainfall in Southeast Arizona.

In a study of moisture surges from the Gulf of California at Yuma, Arizona, a 54-year history of surge events was developed to characterize variability in the frequency and strength of surges entering southwest Arizona from the Gulf of California. An objective relationship for determining surge occurrence and strength at Yuma (Gulf Surge Index, GSI) has been developed; it is now operationally available at: http://whistler.creighton.edu/products/gsi/ Under the last year of our current CPPA funding, a principal research focus has been on identification of key rain bearing transient synoptic features that contribute to summer rainfall in the NAME region. A long-term climatology (1967-2004) of transient synoptic features affecting the NAME region was developed. The climatology includes several synoptic features: inverted troughs, cut off lows, cold fronts and open troughs. Inverted troughs (IVs) at 500mb were found to be the most commonly occurring transient synoptic during the monsoon with a mean frequency of occurrence of 55 days per summer season (June to September). A majority of the IVs crossing northern Mexico are warm core (62%) and these systems can be traced back to the Gulf of Mexico/Caribbean. IVs were found to contribute from 20% to 25% of the average summer rainfall observed in northern Mexico, with warm core IVs more effective rain producers as compared to cold core IVs. Mean daily regional rainfall almost doubles with the presence of an inverted trough.

PACS-SONET ... the final 3 year.s activity and thoughts for the future

Michael Douglas

In April 2006 the Pan American Climate Studies . Sounding Network (PACS-SONET) completed 9 years of operation, during which more than 45,000 pilot balloon observations were made at more than 60 sites in the Americas. This network was funded to improve wind sounding coverage in areas perceived to be important scientifically for describing atmospheric circulation variability at time scales ranging from synoptic through interannual. This poster highlights activities during the last three years of the SONET. In Venezuela, a special study of the diurnal and spatial variability of the llanos low-level jet took place in March 2005, with 7 sites making frequent soundings for 5 days. In Peru, the network expanded with the formal participation of the National Meteorological Service, and a special activity held in southern Peru in early 2006 to measure diurnal variability of the west Andean slope circulations. A Colombian Air Force request led to the establishment of a pilot balloon network, five of which have provided up to twice-daily observations for almost 1 year. In Mexico, the PACS-SONET stations along the Gulf of California continue to play a role in providing a longerterm perspective of the NAME-2004 special observations.

Although formal funding for the PACS-SONET ended in April 2006, a number of stations in different countries continue to make observations. Efforts are being made to determine the best selection of sites that can be maintained as part of a global climate monitoring effort, blending highest scientific priority with operational needs and economic considerations.

Developing cloudiness climatology's from satellite imagery to map cloud Forests and other vegetation features over the tropical Americas

Michael W. Douglas ¹ , John F. Mejia ², and Timothy Killeen ³

¹National Severe Storms Laboratory, Norman, Oklahoma USA

²CIMMS/University of Oklahoma, Norman, Oklahoma USA

³ Conservation International, Washington, D.C.

The environment with the greatest biodiversity from a global standpoint is that known as the tropical Andes .hotspot., which is a broad region along the eastern slopes of the Andes in South America. Within this region, one of the subregions with the highest diversity is the cloud forest, a region of very high cloudiness and high annual precipitation. Mapping this cloud forest and surrounding environments has been of high priority because resources for conservation are limited and conservation organizations and governmental agencies need to know what areas should receive highest priority for protection efforts.

Work associated with the South American Low-level Jet Experiment (SALLJEX) carried out in 2002-3 led to the use of GOES imagery to develop composites for describing the mean cloudiness along the eastern slopes of the Andes. More recently MODIS imagery has been used to describe cloudiness at even higher spatial resolution. Together, these imagery sources can be related to cloud forest distribution. In addition, dry canyon environments, the locus of many geographically-restricted species, can likewise be readily described from the cloudiness composites.

Although the results shown here may not be quantitatively useful for estimating some quantities such as rainfall, their qualitative use should help a broad array of individuals interested in mapping relative cloudiness gradients and identifying suitable areas for ground-based studies. The results should also increase awareness of the importance of mesoclimatological features that are closely tied to topography.

Comparing Multiple Soil Moisture Data Sets to Study Land Surface Hydrological Processes over the US

Y. Fan and H. van den Dool

Y. Fan

Abstract

The exchange of soil moisture and heat between the land surface and the overlying atmosphere is very important for weather and climate prediction. Since soil moisture is one of the controls of the land surface energy and water budgets, and thus impacts the strength of land-atmosphere coupling, understanding and accurately representing spatial and temporal variability of soil moisture is crucially important.

Several soil moisture data sets, such as the observed Illinois soil moisture data set, three retrospective offline run datasets from the Noah land surface model (LSM), VIC LSM and CPC leaky bucket soil model, and three reanalysis datasets (North American Regional Reanalysis, NCEP/DOE Global Reanalysis and ECMWF ERA40), are used to study the spatial and temporal variability of soil moisture and its response to the major components of land surface hydrologic cycles, precipitation, evaporation, runoff and land surface water storage change. Some interesting inter-comparisons are conducted and existing problems are discussed. Over Illinois we compare to observations, but for the US as a whole some impressions can be gained by comparing the multiple soil moisture-evaporation-runoff data sets to each other. The purpose of this study is to quantify the role of dominant land surface hydrological processes and investigate the reasons of soil moisture variability on different spatial-temporal scales, such as where do the low frequency variations in soil moisture come from? What are the magnitudes of major land surface water balance component (Precipitation, Evaporation and Runoff) anomalies on seasonal to inter-annual time scales?

The relationship between oceanic mesoscale motions and atmospheric convection on 10^oN in the eastern tropical Pacificc

J. Thomas Farrar

As part of the Pan American Climate Study (PACS), an air-sea interaction mooring was deployed at 10^oN, 125^oW in the eastern tropical Pacific for 17 months. Computation of the surface layer temperature balance at the site indicates that the dominant influence on the rate of change of upper-ocean temperature at timescales exceeding a few weeks was meridional advection by a quasi-periodic mesoscale velocity signal. Analysis of this signal in the broader spatial and temporal context afforded by satellite altimetry data indicates that this intraseasonal (40 to 100-day period) velocity variability on 10^oN can be interpreted as Rossby waves with some Doppler shifting by the mean westward flow.

The PACS buoy observations further indicate that there is variability in surface solar radiation coupled to the sea surface temperature (SST) signal of the Rossby wave, which suggests that oceanic Rossby waves may affect atmospheric convection by modulating SST. This hypothesis is investigated using satellite measurements of SST, columnar cloud liquid water (CLW), and cloud reflectivity. A statistically significant relationship between SST and these cloud properties is identified within the wavenumber-frequency band of oceanic Rossby waves. Analysis of seven years of data indicates that 10-20% of the variance in CLW at intraseasonal periods and zonal scales on the order of 10° longitude can be ascribed to SST signals driven by oceanic Rossby waves.

Intensification of Southeast United States Summer Rainfall Variability in Recent 30 Years

Rong Fu and Hui Wang

School of Earth and Atmospheric Sciences, Georgia Institute of Technology

Atlanta, Georgia

The Southeast United States is one of the fastest growing regions in the nation. Water supplies in this area are increasingly stressed, especially during summer. Summer droughts in the Southeast thus have vital influence on regional hydrology, agriculture, and related industries. Compared to warm season precipitation in the North American monsoon region and the Great Plains, the variability of Southeast summer precipitation has received less attention in previous studies. On the other hand, precipitation in the Southeast contributes significantly to both mean and variation of warm season rainfall over the continental United States. Understanding the Southeast summer precipitation variability is thus essential for an improved prediction of U.S. warm season rainfall.

Our analysis of 57-yr (1948.2004) rainfall data has revealed that the yearto- year fluctuations in summer rainfall over the Southeast have been intensified in the recent 30 years compared to the earlier period (1948.1975), leading to stronger summer droughts and anomalous wetness. Such intensification of summer rainfall variability is contributed by larger decrease (increase) of rainfall frequency and weakening (strengthening) of rainfall intensity in dry (wet) summers. In both early (1948.1975) and late (1977.2004) periods Southeast summer droughts are associated with decrease of upper-level zonal wind over the southern states and an anticyclonic circulation in the central and eastern United States. Such a circulation pattern favors a stronger Great Plains low-level jet but weaker moisture transport from the Gulf of Mexico to the Southeast. It is found that high interannual variability of upper-level zonal wind over the Great Lakes prior to 1976 shifted to the southern states after 1976. The strong variation in zonal wind over the Gulf coast after 1976 is consistent with the higher interannual variability of Southeast summer precipitation observed since then. The changes of rainfall variability on decadal time scales are correlated to and presumably contributed by a phase shift of the Pacific Decadal Oscillation in 1976 and more variable SST after 1976. An ensemble analysis of 8 global climate model simulations for the 20th and 21st century also suggests that the intensification of summer rainfall variability over the Southeast may be contributed by the effect of global warming.

MODULATION OF RAINFALL BY LAKE TITICACA USING THE WRF MODEL

José Gálvez

CIMMS/University of Oklahoma

And

Michael W. Douglas

NOAA/National Severe Storms Laboratory

Rainfall over Lake Titicaca occurs mainly in the form of nocturnal lakeinduced convective storms. They represent ~55% of the lake.s water input and therefore have implications in climate and paleoclimate scales. This study uses the Weather Research and Forecasting (WRF) model to investigate the role of the lake in the modulation of these storms. The goals are to improve regional weather and climate forecasts and to provide information about the role of lakes on dry-to-wet transitions in the altiplano. The results point to low-level convergence and moisture as essential for the development and maintenance of the storms. The mid-tropospheric flow also seems to play an important role in their enhancement or suppression based on the interaction with local circulations induced by orography. Weak southeasterly flow favors storm development. Strong flow, especially from the northeast, suppresses storm development by shifting the region of low-level convergence away from the source of heat and moisture.

Some sensitivity studies are being run on the effect of paleolake Tauca on the climate of the altiplano; results will be presented.

INTERANNUAL VARIATIONS IN WARM SEASON STREAMFLOW IN NORTHWEST MEXICO

David J. Gochis, National Center for Atmospheric Research, Boulder, CO, USA

Luis Brito-Castillo, CIBNOR, Guaymas, Sonora, Mexico

W. James Shuttleworth, Dept. of Hydrology and Water Resources, U. Arizona, Tucson, AZ, USA

Hydroclimatological analysis of the North American Monsoon region of northwest Mexico reveals significant regions of seasonal precipitation and streamflow coherence. In this work, inter-annual variations in regionalized rainfall-runoff relationships are explored. Modulation of precipitation by largescale forcing mechanisms such as tropical and North Pacific sea surface temperatures seems to have a non-linear effect on runoff generation whose response varies by region. Analyses reveal that the El Nino-Southern Oscillation (ENSO) exerts a modest but statistically significant influence on NAM streamflow. Different ENSO indices exhibit markedly different correlation structures with NAM sub-regions. The occurrence of ENSO also has a significant impact on the partitioning of streamflow between the summer and winter seasons. The summer ENSO influence is explained, in part, by changes in the lower tropospheric pressure and wind fields. These changes result in modest increases in moisture availability (higher PW) fields during La Nina episodes vs El Nino episodes. Based on these results, the effects of ENSO variability need to be accounted for in applying regional downscaling techniques to parent forecast models which have difficulty representing warm season ENSO responses.

RECENT FINDINGS FROM THE NAME EVENT RAIN GAUGE NETWORK (NERN)

David J. Gochis, National Center for Atmospheric Research, Boulder, CO, USA

Christopher J. Watts, U. Sonora, Hermosillo, Sonora, MX

Julio-Cesar Rodriguez, IMADES, Hermosillo, Sonora, MX

Jaime Garatuza-Payan and Iran Cardenas, ITSON, Cd. Obregon, Sonora, MX

Wei Shi, CPC/NCEP/NWS/NOAA, Camp Springs, MD, USA

The NAME Event Raingauge Network (NERN) provides event rainfall measurements at more than 90 locations in the core North American Monsoon region of northwest Mexico. The value of the NERN data archive continues to grow with the acquisition of each new season of data. Recent analyses using NERN data have focused on characterizing the variability of precipitation intensity, frequency and total accumulations as functions of time-scale and season. These analyses characterize a precipitation regime that shows significant variability at between seasons and an evolution of the precipitationelevation relationship as a function the annual cycle. The NERN has also recently been used to assess remotely sensed estimates of precipitation characteristics from the PERSIANN product. Combined, NERN data and analyses are contributing to a greatly improved process understanding of precipitation in northwest Mexico and highlight the utility of the network as a critical component of a regional climate observing system.

The Precipitation Climatology of the Western United - Part I: Raingauge and Satellite Data Analysis

Kristen Goris

The goal of this project is to use very-high resolution model simulations together with observationally-based precipitation data to improve our ability to make hydrometeorological predictions at various space/time scales in the western United States. Specifically, we aim to enhance our predictive capability by defining the roles of land surface processes (soil moisture, vegetation and the orography of the Western Cordillera) in modulating the hydrometeorology there. This first stage of the project uses principal component-based regionalization techniques to isolate regions having distinct precipitation climates and investigates whether the results of the regionalization are dataset dependent. Principal component-based regionalization methods are important tools in atmospheric and climate research. Several studies have used such eigentechniques with data from raingauge networks to study regional precipitation regimes in order to identify patterns of precipitation covariability. However, the reality that many parts of the world are covered sparsely by, or are completely void of, such networks limits the scope of these types of studies. In this first stage of the project we examine the utility of satellite-based data products for regionalization studies by conducting a comparative regionalization of the precipitation climate of the western United States using raingauge and satellite data. Specifically, we (i) assess the degree of sensitivity of the rotated principal component solution to changes in spatial resolution and temporal domain and (ii) test the degree of similarity between solutions obtained using raingauge versus satellite-based data products.

The rotated loading patterns are found to exhibit a marked influence by topography as is indicative of the precipitation climate in the western United States. The methodology is shown to be stable to changes in spatial resolution and temporal domain. The rotated principal component solution additionally shows stability across datasets. The results suggest that satellite data may in fact be a useful tool in regionalization studies, which has implications for raingauge installation and planning, climate research, and numerical modeling experiments.

Interannual Variability of Near-Coastal Eastern Pacific Tropical Storms

David S. Gutzler

Interannual fluctuations of tropical storms affecting the west coast of North America are modulated by the ENSO cycle and by Pacific decadal variability, during the early months of the warm season. More tropical storms affect the Pacific coast in May-July during La Niñears (when equatorial Pacific Ocean temperature is anomalously cold) than during El Niñears. The difference between La Niñnd El Niñears was particularly pronounced during the mid-20th Century epoch when cold equatorial temperatures were enhanced, as described by a standard index of the Pacific Decadal Oscillation.

NAMAP2 and the NAME Climate Process Team

D. Gutzler1, L. Williams2, and NAMAP2 contributing modeling teams

1 Dept. of Earth & Planetary Sciences 2 NOAA Climate Prediction Center

University of New Mexico 5200 Auth Road

Albuquerque, NM 87131 USA Camp Springs, MD 20746 USA

[gutzler@unm.edu] [lindsay.n.williams@noaa.gov]

We present initial results from the second phase of NAMAP (called NAMAP2), a model assessment effort associated with the North American Monsoon Experiment. The simulations provide a set of comparable runs for the North American warm season of 2004, during which NAME enhanced monitoring took place in the field. This project is a follow-on to the pre-field phase set of simulations known as NAMAP (Gutzler et al. 2004), which established benchmarks for model improvement based on common simulation of an earlier year (1990). Results from NAMAP2 will feed into operational model development at NCEP via the NAME Climate Process Team. NAMAP2 simulations were completed early this year; results and assessment are ongoing.

Evaluation of the NCEP Regional Reanalyses over Complex Terrain

John Horel

Spurious grid-scale precipitation occurs in many mesoscale models when the simulated atmosphere becomes convectively unstable and the convective parameterization fails to relieve the instability. SGSP events are also found in the North American Regional Reanalysis (NARR) and are accompanied by excessive maxima in grid-scale precipitation, vertical velocity, moisture variables (e.g., relative humidity and precipitable water), mid- and upper-level equivalent potential temperature, and mid- and upper-level absolute vorticity. SGSP events in environments favorable for highbased convection can also feature low-level cold pools and sea level pressure maxima.

Prior to 2003, retrospectively generated NARR analyses feature an average of ~370 SGSP events annually. Beginning in 2003, however, NARR analyses are generated in near-real time by the Regional Climate Data Assimilation System (R-CDAS), which is identical to the retrospective NARR analysis system except for the input precipitation and ice cover datasets. Analyses produced by the R-CDAS feature a substantially larger number of SGSP events with more than 4000 occurring in the original 2003 analyses. An oceanic precipitation data processing error, which resulted in a reprocessing of NARR analyses from 2003-2005, only partially explains this increase since the reprocessed analyses still produce ~2000 SGSP events annually. These results suggest that many NARR SGSP events are not produced by shortcomings in the underlying Eta model, but by the specification of anomalous latent heating when there is a strong mismatch between modeled and assimilated precipitation.

NARR users should ensure that they are using the reprocessed NARR analyses from 2003-2005 and consider the possible influence of SGSP on their findings, particularly after the transition to the R-CDAS. Programmatic efforts to develop a high-resolution analysis of record will also be discussed.

Experimental Medium-range Ensemble Streamflow Forecasts Based on Coupled GFS-Noah Ensemble Runoff Forecast

Dr. Dingchen Hou

Environmental Modeling Center/NCEP/NOAA

Dingchen.hou@noaa.gov

Co-authors

Kenneth Mitchell, Zoltan Toth, EMC/NCEP/NOAA

Dag Lohmann, Risk Management Solution Ltd.

and Helin Wei, EMC/NCEP/NOAA

A major thrust of CPPA is directed toward improving the utility of seasonal hydrological predictions for water resource management. Since seasonal precipitation forecasts exhibit large uncertainties, seasonal hydrologic forecasts must be framed in a probabilistic form, following an ensemble forecast approach. At the National Centers for Environmental Prediction (NCEP), the recent coupling of the Noah Land Surface Model (Noah LSM) to the global atmospheric model of the NCEP Global Forecast System (GFS) . including in the GFS-based Global Ensemble Forecast System (GEFS) -- in combination with the streamflow routing scheme previously developed for the NCEP N. American Land Data Assimilation System (NLDAS), provided the means for exploring the feasibility of coupled medium-range ensemble streamflow prediction. This study represents the precursor to a near-future follow-on study for the intra-seasonal and seasonal range using the ensemble seasonal predictions of the NCEP Climate Forecast System (CFS) coupled to the Noah LSM.

To generate streamflow initial conditions (which we also use for forecast evaluation), observed precipitation values and other land surface forcing from NCEP's mesoscale N. American Data Assimilation System (NDAS) are used to force the NLDAS system, which produces the analysis of runoff fields that drive the attendant streamflow routing model in analysis mode. Experimental mediumrange ensemble streamflow forecasts are then generated by forcing the same streamflow routing model with the ensemble of predicted runoff fields from the coupled land-atmosphere GFS/Noah model, as executed in ensemble mode in the operational GEFS system. Both the GFS/Noah runoff predictions and streamflow routing network are represented on the1/8-degree latitude/longitude CONUS grid of the NLDAS.

A subjective evaluation of the preliminary experiments reveals the following features at short- to medium-range lead times: (1) the variability in the ensemble streamflow forecasts is of the same order of magnitude as the error in the mean of the ensemble, (2) for large basins, the ensemble streamflow forecasts appear to capture well the variations in the NLDAS analysis of streamflow, and (3) for medium- and small-sized basins, a serious under-dispersion is present in the spread of the ensemble streamflow forecasts (likely due to a lack of sufficient variability in the precipitation forcing on the scale of the chosen river basin).

The Pan-American Precipitation Pattern and its tropical connections

Huei-Ping Huang

Huei-Ping Huang, Richard Seager, Yochanan Kushnir

(E-mail: huei@ldeo.columbia.edu)

Lamont-Doherty Earth Observatory of Columbia University

Observational analyses and numerical simulations show that when the Southwest U. S. and Mexico are wetter than normal, Northern and South-Central South America are drier and wetter than normal, respectively. The positive (wet Southwest U. S.) and negative phases of this Pan-American Precipitation Pattern recur on interannual to interdecadal time scales. Its variability is shown to be strongly influenced by the tropical Pacific SST anomalies due to El Nino and the decadal-to-interdecadal changes in the tropical ocean circulation. Although the Pan-American Precipitation Pattern (PAPP) projects onto the canonical ENSO response in precipitation, the former is more general because it can also be reproduced by atmospheric GCMs forced with the observed interdecadal change in the tropical SST that does not resemble an ENSO SST anomaly. Numerical simulations indicate that the mean condition of the tropical Pacific SST anomaly is relevant in determining the polarity of the PAPP. A warm tropical Pacific corresponds to a (wet, dry, wet) pattern in precipitation for (Southwest U. S., Northern South America, South-Central South America). A cold tropical Pacific corresponds to the opposite phase with a dry condition in the Southwest U. S. related to prolonged droughts in that region. The statistical significance of this tropical SST-North American drought relationship is established with ensemble GCM simulations for recent and historical droughts. The tropical influences on extratropical precipitation are accomplished by two types of zonally symmetric and asymmetric processes. The zonally asymmetric response is dominated by a Rossby wave train that is forced mainly by the Eastern Pacific SST anomalies. The zonally symmetric component involves a more complicated interplay between the tropical tropospheric temperature response and the changes in storm track induced by the tropical SST anomalies. The detail of these processes will be discussed.

Mid-level and Deep Convective Cloud Characteristics across the Tropical Pacific

Michael P. Jensen

Convective clouds of various shapes and sizes are an obvious feature in satellite images of tropical latitudes due to their high shortwave albedos. However, depending on the atmospheric state and large-scale dynamics different convective cloud types can develop. Within a given convective cloud type we may also observe great variability in cloud macro- and microphysical properties. These different cloud types and cloud characteristics may have vastly different impacts on the local water and energy budgets.

We use ship-based remote sensing observations and soundings from the EPIC 2001 field experiment coupled with a simple entraining parcel model in order to address the following questions about deep convective cloud types: 1) Which environmental factors play a role in determining the depth of tropical convective clouds? 2) What environmental parameters are related to entrainment rate in cumulus congestus clouds? We compare these results to previous (Jensen and Del Genio 2006) and ongoing analysis in the tropical Western Pacific. Our results suggest that in regions with a relatively low frequency of deep convection a drying of the mid-troposphere is a more likely to be responsible for limiting convective cloud-top heights than a stabilizing of the freezing level. We also find that low-level CAPE and the RH profile account for the largest portion of the variance in cumulus congestus entrainment rates, consistent with the idea that entrainment rate depends on the buoyant production of turbulent kinetic energy. Initial results from the Eastern Pacific ITCZ (EPIC 2001) indicate that in regions with more intense deep convection the stability at the freezing level plays a much more important role in limiting the depth of cumulus congestus clouds.

We also present some results from the analysis of several years of observations of tropical deep convective systems by the Moderate Imaging Spectroradiometer (MODIS) aboard NASA.s Terra and Aqua satellites. The statistical analysis involves the determination of cloud-averaged values of several important cloud properties (e.g. cloud particle effective size, cloud-top temperature, optical thickness, cloud-top pressure, shortwave albedo). We use a cloud identification algorithm to define convective cloud systems. Our analysis concentrates on two regions of the Pacific Ocean, the tropical eastern Pacific region (as sampled during the EPIC 2001 ITCZ) and the tropical Western Pacific, which has a history of field projects (TOGA COARE) and long-term monitoring sites (ARM).

Diurnal Cycle of Sea Surface Winds and Temperatures during NAME

Richard Johnson

The 2004 North American Monsoon Experiment (NAME) had a key objective of exploring the large-scale circulation patterns and their diurnal variation over northwestern Mexico and the southwestern United States, and how they relate to the onset and evolution of the North American Monsoon. For this study, the core of the Enhanced Observing Period spanned 1 July - 15 August. This work examines surface winds and temperatures over oceanic regions using high-resolution satellite products with particular emphasis on NASA's Quick Scatterometer (QuikSCAT). The monsoon contributes a substantial fraction of the annual precipitation in northwest Mexico and the southwest US. This study shows that surface winds just offshore in the NAME region are significantly modulated by sea and land breezes and that the spatial extent of this modulation varies from pre- to post-monsoon onset.

Moreover, there are important interannual variations of surface wind and SST, which will be reported on in this paper.

Reprocessed Historical Hydrometeorological Automated Data System (HADS) Precipitation Data in National Climatic Data Center

Dongsoo Kim and Brian Nelson

NOAA/NESDIS/National Climatic Data Center

The Hydrometeorological Automated Data System (HADS) is a real-time and near real-time data acquisition, processing and distribution system operated by the Office of Hydrologic Development (OHD) of the National Weather Service (NWS). The system has been operational since 1996 and the real-time data are used at the NWS River Forecast Centers (RFC) for hydrologic modeling (i.e., flood forecasting) and for adjustment of radar-rainfall estimates in the Multi- Sensor Precipitation Estimation (MPE) algorithm.

Recently, NOAA.s National Climatic Data Center (NCDC) became the archival custodian of the real-time HADS data as well as historical HADS data and as part of data quality measures, we have reprocessed all of the precipitation data (HADS includes several other hydrometeorological variables) from the original Shared Hydrometeorological Exchange Format (SHEF). A similar hourly precipitation data set which is processed from the real-time HADS at Climate Prediction Center (CPC) has been an important resource, and was archived and made available to the user from UCAR with the support of the GEWEX Continental-Scale Intercomparison Project. Our reprocessing scheme has recovered many precipitation estimates that were otherwise recorded as missing in the UCAR archive. An hourly precipitation product we call the baseline product is the result a simple recovery of missing values when the accumulated precipitation is identical before and after missing periods. The next step, the level 1 product, is an output of quality control applied to the baseline product to remove false precipitation that results in negative precipitation. The level 2 product is an output of a spatial consistency check within +/- 0.5 degrees latitude/longitude. The level 3 product is an output of a consistency check with NEXRAD radar based precipitation estimates. These reprocessing steps are not possible in real-time. Thus this products differs from the UCAR archived product We present the steps involved in reprocessing and the added value of reprocessed HADS precipitation as compared to the UCAR archived hourly precipitation. We provide three important measures for comparison:

(1) Recovery of missing values.

(2) Assignment of the correct observation time stamp for SHEF processed files.

(3) The value added product as seen at monthly and longer scales.

A beta version of the hourly precipitation product will be available in late 2006. Other levels of precipitation product will be available with added QC later. The level 3 product will depend on the output of Multi-sensor Precipitation Reanalysis (MPR) which is an ongoing collaborative project of NCDC with the National Weather Service Office of Hydrologic Development (OHD). The MPR is an extension of and re-engineering of the real-time MPE run by NWS River Forecast Centers (RFC).

A comparison of orographic precipitation simulated using high spatial resolution and a subgrid parameterization

L.R. Leung

Regional downscaling is expected to have the largest impacts on simulating precipitation and surface hydrological processes in regions with complex orography. Two dynamical downscaling methods have been successfully used in the past to simulate regional climate change and assessing its impacts in mountainous regions. The first approach uses regional climate models (RCMs) to simulate the effects of orography on clouds and precipitation. As RCMs are applied to smaller geographic regions, higher spatial resolution can be achieved to explicitly resolve orographic effects such as rainshadowing. Several studies, however, have suggested a tendency for the simulated regional mean precipitation to increase with increasing spatial resolution, leading to wet biases in high resolution simulations. The second approach applies subgrid parameterizations in climate models to simulate orographic effects. In the subgrid method developed by Leung and Ghan, precipitation is simulated for a small number of subgrid elevation classes within each model grid cell. During postprocessing, the subgrid variables are mapped geographically based on the location and surface elevation of the model grid cells and subgrid classes to generate high resolution spatial distributions of precipitation and snowpack. This approach is computationally efficient, but rainshadow effects are only resolved at the explicit grid resolution, since areas belonging to the same subgrid elevation class within a grid cell receive the same amount of precipitation regardless of its orientation with respect to the topographic gradients.

To gain a better understanding of the strengths and weaknesses of these two approaches and to guide future developments, this study compares simulations performed using the Weather Research and Forecasting (WRF) model at 30, 15, and 5 km spatial resolutions for the western U.S. with a global climate simulation using the Community Atmosphere Model (CAM) with the subgrid orographic precipitation scheme. Precipitation characteristics and surface water budgets simulated by the models for both the warm and cold seasons will be compared against observations to understand model biases.

A Proposed Definition for Rainy Season Onset and Demise

Brant Liebmann

A definition is proposed to determine onset of the rainy season. The definition is objective in that it is based on rainfall accumulation anomalies relative to the local climatology. The definition implicitly disregards 'false starts.' It is shown that in almost any area, onset and ending are marked by large jumps in rainfall.

Theory of convective margin shifts under tropospheric warming

B R. Lintner

Regional precipitation anomalies under El Nino or global warming scenarios manifest considerable spatial sensitivity, especially in the vicinity of tropical deep convective zones. Using a simplified set of equations, we develop an analytic prototype of convective margins for tropical land regions, focusing on the importance of inflow from ocean regions. This approach yields expressions for the location of the convective margin, from which it is straightforward to deduce how perturbations in climate impact the margin. We compare the results of the prototype to full model simulations of the equatorial South American precipitation response to El Nino forcing and find general agreement. Analysis of the observations further supports the basic validity of the inflow convective margin prototype.

Merging a high-resolution meteorological distribution model (MicroMet) with a detailed snow-evolution model (SnowModel)

Glen E. Liston

An intermediate-complexity, quasi-physically-based, meteorological model (MicroMet) has been developed to produce high-resolution (e.g., 30-m to 1-km horizontal grid increment) atmospheric forcings required to run spatially distributed terrestrial models over a wide variety of landscapes. The following seven variables, required to run most terrestrial models, are distributed: air temperature, relative humidity, wind speed, wind direction, incoming solar radiation, incoming longwave radiation, and precipitation. To produce these distributions, MicroMet assumes at least one value of each of the following meteorological variables are available for each time step, somewhere within, or near, the simulation domain: air temperature, relative humidity, wind speed, wind direction, and precipitation. These variables are collected at most meteorological stations. MicroMet includes a preprocessor component that analyzes meteorological data, then identifies and corrects potential deficiencies. Since providing temporally and spatially continuous atmospheric forcing data for terrestrial models is a core objective of MicroMet, the preprocessor also fills in any missing data segments with realistic values. Data filling is achieved by employing a variety of procedures, including an AutoRegressive Integrated Moving Average calculation for diurnally varying variables (e.g., air temperature). To create the distributed atmospheric fields, spatial interpolations are performed using the Barnes objective analysis scheme, and subsequent corrections are made to the interpolated fields using known temperature-elevation, windtopography, humidity-cloudiness, and radiation-cloud-topography relationships.

MicroMet has been merged with SnowModel, a spatially-distributed snowevolution modeling system designed for application in landscapes, climates, and conditions where snow occurs. It is an aggregation of four sub-models: MicroMet defines meteorological forcing conditions, EnBal calculates surface energy exchanges, SnowPack simulates snow depth and water-equivalent evolution, and SnowTran-3D accounts for snow redistribution by wind. Simulated processes include snow accumulation; blowing-snow redistribution and sublimation; forest canopy interception, unloading, and sublimation; snow-density evolution; and snowpack melt. Conceptually, SnowModel includes the first-order physics required to simulate snow evolution within each of the global snow classes (i.e., ice, tundra, taiga, alpine/mountain, prairie, maritime, and ephemeral). Here we present our application of MicroMet/SnowModel to the mountains of Colorado as part of the Cold Land Processes Field Experiment (CLPX).

A hydrological ensemble seasonal forecast system over the Eastern U.S.

Lifeng Luo

Progress in diagnosing, modeling and predicting seasonal climate variability represents a major scientific advancement of the 20th century, however, progress in the effective utilization of forecasts has lagged behind (Goddard et al, 2001). This research builds on an experimental seasonal hydrologic forecast system in the Ohio River basins to address a central scientific question of whether seasonal climate predictions have sufficient skill to provide improved hydrologic forecasts and water management information across the eastern U.S., as well as consider how seasonal hydrologic predictions can be made most skillful given the climate predictions, and how this skill can be quantified. The project focuses over the eastern U.S., and carries out the following two major activities:

1) The development of an expanded Eastern U.S. hydrologic ensemble forecast system that will include all basins east of the Mississippi main stem up to the mouth of the Ohio River.

2) An evaluation and analysis of the resulting seasonal hydrological predictions, with a focus on understanding the reliability of the ensemble forecasts and the overall uncertainty in the hydrologic ensembles due to model (seasonal climate and hydrologic) uncertainty, calibration uncertainty, data uncertainty, and so forth.

The project will enhance NOAA operational activities by extending current links to the NCEP-lead LDAS activities, by providing results useful for the NWS/HDL proposed water initiative and by demonstrating the usefulness of the seasonal hydrologic forecasts through application studies.

Intraseasonal Variability of the South American Monsoon System

Hsi-Yen Ma

Department of Atmospheric and Oceanic Sciences, UCLA

hyma@atmos.ucla.edu

Co-Author:

C. Roberto Mechoso, Department of Atmospheric and Oceanic Sciences, UCLA

We have been examining the intraseasonal variability of the South American Monsoon System (SAMS) using observational datasets and the UCLA AGCM simulations for the southern summer (December-January-February). One principal goal is to explore the diurnal cycles of rainfall in locations affected by SAMS.

For selected locations in Amazonia and the South Atlantic Convergence zone (SACZ) the NCEP Reanalysis and simulation data reveal that the anomalous (in reference to the climatology) low-level wind can be steadily from the west (as in the seasonal mean) or from the east during periods at least several (three-to-ten) day-long (westerly and easterly wind regimes or WWR and EWR, respectively). In both wind regimes the composites of anomalous precipitation over South America show a dipole pattern with poles in northwestern and central-southeastern Brazil (over the Andes and in centralsoutheastern Brazil) in the Reanalysis (in the simulation). During WWRs (EWRs) precipitation anomalies in the central-southeastern pole are positive (negative) implying a stronger (weaker) SACZ. During WWRs the monsoon high at upper levels is stronger and the subtropical jet in the South American sector is stronger and closer to the equator. Also, there is enhanced cyclonic flow over southeastern South America. The EOF analysis shows the wind regimes may be associated with the downstream development of the Pacific South American (PSA) patterns or .modes..

The diurnal cycle of rainfall from three CEOP Model Output Time Series (MOLTS) in Rondonia (Brasilia) in the different poles of the dipole in rainfall anomalies is examined. The diurnal cycle has an early afternoon maximum in the two selected locations during both regimes. There is, however, an interesting difference between regimes. In Rondonia (Brasilia), days in the EWRs (WWRs) show another early morning (nocturnal) maximum that contributes to the higher diurnal mean rainfall in this regime. In the simulation, WWRs and EWRs appear with approximately the same frequency. There is also a dipole pattern in the anomalous precipitation during days in the regimes, albeit poles are displaced. The diurnal cycles of rainfall in the different wind regimes are nearly identical. It is argued that there are significant differences between the diurnal cycles of the SAMS rainfall in days belonging to the different wind regimes in SAMS. The reasons for this low-frequency variability is been investigated.

Statistical Downscaling of the Warm Season Precipitation in the Core North America Monsoon Region

Kazungu Maitaria

Kazungu Maitaria, Dave Gochis, Steve Mullen, Dave Yates & Jim Shuttleworth

The North America Monsoon System (NAMS) is the principal feature of summer climate of Mexico and the southwest U.S. This study explores the veracity of statistically downscaled forecasts of warm season precipitation over the core region of the North American Monsoon Experiment (NAME). Normalized, 24-h precipitation anomalies for northwest Mexico during the 49 summers of 1950 to 1998 are subjected to a rotated empirical orthogonal function procedure that identifies three contiguous precipitation regions, each of which is analyzed separately. Using output variables from the National Centers for Environmental Prediction 1998 medium-range forecast (MRF) model, we determine which variables are important predictors of the hydrometeorological and boundary layer features associated with NAMS rainfall. Predictor choice is important because it has a pronounced impact on the performance of the downscaling algorithm when evaluated against station observation data for the period 1979-1998. The K-Nearest Neighbor algorithm (KNN), an analog-type downscaling technique, is applied to derive local-scale predictions of precipitation from specified MRF model variables. For a given grid point, the KNN matches the featured day ensemble fields with archived predictors by employing principal component-based technique to identify a subset of days (K) similar to the feature day. An ensemble of 105 members (15 medium range forecasts ï 7 statistical predictions) is used to define an estimate of local precipitation. The quality of the downscaled forecasts is evaluated by a comprehensive suite of verification metrics to quantify how well the model captures the space-time variability of the weather fields at each individual station. The verification suite includes estimates of bias, ranked probability skill score, spatial covariance between stations, temporal persistence, consistency between variables, and conditional bias to develop spread-skill relationships.

Boreal Summer Intraseasonal Variability and Air-Sea Interaction in the Tropical Northeast Pacific

Eric D. Maloney

We present an analysis of eastern north Pacific intraseasonal variability during June-September using satellite and buoy observations. QuikSCAT ocean vector winds and TRMM precipitation indicate that periods of anomalous surface westerly flow over the east Pacific warm pool during an intraseasonal oscillation (ISO) lifecycle are generally associated with an enhancement of convection over the east Pacific warm pool. Periods of surface easterly anomalies are generally associated with suppressed convection. Enhanced wind speed occurs during the ISO westerly phase associated primarily with southwesterly intraseasonal vector wind anomalies adding constructively to the climatological southwesterly flow, with a much weaker contribution from enhanced eddy wind variability on timescales of less than 20 days. Suppression of wind speed occurs during the ISO easterly phase with equal contributions from northeasterly intraseasonal vector wind anomalies adding destructively to the climatological southwesterly flow and strong suppression of eddy activity.

The increase in wind speed during periods of ISO westerly anomalies implies an increase in the wind-induced component of latent heat flux. TAO buoys along the 95W line are used to examine the relationship between intraseasonal precipitation and latent heat flux. A statistically significant correlation between intraseasonal latent heat flux and precipitation occurs in the east Pacific warm pool, consistent with previous studies suggesting a role for wind-evaporation feedback in supporting intraseasonal convection there. Intraseasonal latent heat flux anomalies at all buoys are primarily wind-induced.

Wind jets in the Gulf of Tehuantepec and Gulf of Papagayo appear to be active during periods of ISO easterlies and suppressed convection. The composite total wind vector in the Gulf of Papagayo and Gulf of Tehuantepec during ISO westerly phases is close to that in the June-September mean.

Eight years of TMI SST data in conjunction with the shorter east Pacific warm pool TAO buoy record are used to examine ISO-related SST variability. A statistically significant spectral peak in summertime east Pacific warm pool sea surface temperatures is observed at a timescale about 50 days, associated with the ISO. Composite SST variations of 1°C occur over parts of the warm pool, with the SST leading ISO convection and westerly wind anomalies by about 5-10 days. Buoy surface radiative, heat, and momentum fluxes are being used to determine the processes responsible for SST regulation during an ISO lifecycle.

Annual Cycle Explorer (ACE)

Brian Mapes

GUI driven software for viewing the annual cycle in climate datasets, with special emphasis on high-frequency features, will finally be released! The software runs right off a CD or DVD with two clicks, on any PC, Mac or Linux platform. Come see, get a copy.

Diurnal Cycle of Sea Surface Winds and Temperatures during NAME 2004

Brian D. McNoldy

Colorado State University

mcnoldy@atmos.colostate.edu

Richard H. Johnson

Colorado State University

johnson@atmos.colostate.edu

Paul E. Ciesielski

Colorado State University

paulc@atmos.colostate.edu

The monsoon contributes a substantial fraction of the annual precipitation in northwest Mexico and the southwest US. The study shows that surface winds just offshore in the NAME region are significantly modulated by sea and land breezes and that the spatial extent of this modulation varies from pre- to postmonsoon onset. Moreover, there are important interannual variations of sea surface winds and temperatures, which will be reported in this paper.

26-year global land climatology for the NOAA Climate Test Bed

Jesse Meng

Accurate assessment of land surface states, namely, soil moisture, soil temperature, vegetation, and snowpack, is critical in numerical weather and climate prediction systems because of their regulation of surface water and energy fluxes between the surface and atmosphere over a variety of spatial and temporal scales. To provide the NOAA Climate Test Bed (CTB) optimal land climatology, an uncoupled, land-component only, Land Information System (LIS) has been implemented. LIS, developed primarily by NASA Goddard Space Flight Center (GSFC) with close collaboration with NOAA National Centers for Environmental Prediction (NCEP), aims to perform high-quality land surface simulation using state-of-art land surface models (LSMs) and further minimizes the errors of simulation by constraining the LSMs with observation-based precipitation and radiation, and satellite land data assimilation techniques. The LIS infrastructure has been ported to the NCEP supercomputer that serves the CTB framework. In this implementation, the NCEP Global Reanalysis-2 and the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) will be used to drive the Noah LSM to perform uncoupled land surface simulation experiments. The latest version of Noah LSM has been coupled to the operational NCEP Global Forecast System (GFS) for weather prediction and test bed versions of the NCEP Climate Forecast System (CFS) for climate prediction. It is crucial that the uncoupled LIS/Noah use exactly the same Noah code (and soil and vegetation parameters therein), and execute on the same horizontal grid, landmask, terrain field, soil and vegetation types, seasonal cycle of green vegetation fraction and surface albedo as in the coupled GFS/Noah and CFS/Noah. To support CTB, LIS/Noah will be executed on the same T126 gaussian grid as of CFS, for the period of 1980-2005, starting with pre-execution 10-year spin-up, to generate the 26-year retrospective global land surface states. This LIS/Noah retrospective will be used for the global land surface climate variability assessment and land initial conditions for the ensemble CFS seasonal hindcast experiments. Finally, this LIS/Noah retrospective will provide the global land climatology and anomaly needed as the foundation for a global drought/flood monitoring system that includes realtime updates of the land surface states.

Seasonal Influence of ENSO on the Atlantic ITCZ and equatorial South America

Matthias Munnich

In late boreal spring observed precipitation anomalies over equatorial South America and the Atlantic intertropical convergence zone (ITCZ) show a significant correlation with eastern equatorial Pacific and central equatorial Atlantic sea surface temperature anomalies (SSTA).

Correlations between equatorial Pacific SSTA, equatorial Atlantic wind stress, SSTA, sea surface height, and ITCZ precipitation suggest causal chain in which El Nino/Southern Oscillation (ENSO) induces western equatorial Atlantic wind stress anomalies, which in turn affect Atlantic equatorial ocean dynamics. These correlations show strong seasonality, apparently arising within the atmospheric links of the chain.

This pathway and the influence of equatorial Atlantic SSTA on South American rainfall in May appear independent of that of the northern tropical Atlantic. Brazil's Nordeste is affected by the northern tropical Atlantic while the equatorial influence lies further to the north over the eastern Amazon and the Guiana Highlands.

Variability of the cross-equatorial flow over the eastern Pacific Ocean from 8 years of pilot balloon observations at Piura, Peru

Javier Murillo¹, Michael W. Douglas², Norma Ordinola³ and Luis Flores³

¹CIMMS/University of Oklahoma, Norman, Oklahoma USA

²National Severe Storms Laboratory, Norman, Oklahoma USA

³ University of Piura, Piura, Peru

Pilot balloon observations have been made at Piura, Peru (~5.2˚S) since 1997 as part of the PACS-SONET project. These observations were begun as an effort to measure possible cross-equatorial flow variations that might be related to rainfall variations in Central America. Originally, observations were to have lasted for 6-months, but observations were extended because of the 1997-8 El Niñvent, and then variously extended until the present. This data set is the most complete set of observations from SONET, with the only major gap in observations due to a period when a boundary layer wind profiler was operating at Piura (this profiler has a much more .gappy. record due to hardware failures). The mean winds at Piura show that even with unfavorable cloudiness conditions it is possible to obtain monthly mean values of the wind that are sufficiently accurate to describe intraseasonal to interannual variations. The requirement is of course that the standard deviation of the winds about the mean be not excessively large compared with the variations which one seeks. The large signal associated with the 1998 El Niñvent stands out as the most prominent feature of the 8-year record, although the cool year of 2005 showed a significant departure from the 8-year mean in the opposite sense.

The initiation and upscale growth of convection within the diurnal cycle along the Sierra Madre Occidental

Stephen W. Nesbitt (snesbitt@uiuc.edu)

This study will examine modes and variability in the diurnal cycle of deep convection tied to topography within the NAME Tier-1 domain during the 2004 EOP. Specifically, ground-based precipitation retrievals the NAME Event Rain gauge Network (NERN) and polarimetrically- and NERN- tuned CSU/NCAR version 2 radar composite precipitation estimates over the southern NAME Tier-I domain will be compared with rainfall estimates from the CMORPH, TRMM 3B42, and PERSIANN to examine the timing and magnitude of the diurnal cycle along the western slopes of the Sierra Madre Occidental (SMO). In addition, half-hourly images of 11-micrometer brightness temperatures from GOES will be analyzed to examine the modes of vertical development of convection as a function of topography and the diurnal cycle. Furthermore, vertical profiles of radar reflectivity from the TRMM precipitation radar will be examined to elucidate convective vertical structure as a function of topography in context with the GOES results.

Preliminary results, confirming the inference of Hong et al. (2006, conditionally accepted in J. Hydromet.) show that over the highest terrain (above 2000 m), shallow convection tends to form just west (downwind) of the highest terrain just before local noon, and thus warm rain microphysical processes are important in rainfall production early in the diurnal cycle. The onset of deep convection (defined as cloud tops which reach a cold IR brightness temperature less than 208K) is delayed until 1500 LT, and occurs almost exclusively in terrain below 2000 m elevation, where it continues to grow upscale and organize into mesoscale convective systems. In this poster, we will examine the intraseasonal variation in these processes, as well as the environments that control deep convective growth by examining limited surface thermodynamic data available in the high terrain of the SMO during the NAME EOP.

Observed vegetation-climate feedbacks in the United States

Michael Notaro

Observed vegetation feedbacks on temperature and precipitation are assessed across the United States using satellite-based fraction of photosynthetically active radiation (FPAR) and monthly climate data for the period of 1982.2000. This study represents the first attempt to spatially quantify the observed local impact of vegetation on temperature and precipitation over the United States for all months and by season. Lead.lag correlations and feedback parameters are computed to determine the regions where vegetation substantially impacts the atmosphere and to quantify this forcing. Temperature imposes a significant instantaneous forcing on FPAR, while precipitation's impact on FPAR is greatest at one-month lead, particularly across the prairie. An increase in vegetation raises the surface air temperature by absorbing additional radiation and, in some cases, masking the high albedo of snow cover. Vegetation generally exhibits a positive forcing on temperature, strongest in spring and particularly across the northern states. The local impact of FPAR on precipitation appears to be spatially inhomogeneous and relatively weak, potentially due to the atmospheric transport of transpired water. The computed feedback parameters can be used to evaluate vegetation.climate interactions simulated by models with dynamic vegetation.

Effects of Surface Moisture, Land-Atmosphere Exchanges, \par and Turbulent Transport on Precipitation over the Rocky Mountains and High Plains

M. Pagowski

The ratio of how much precipitation comes from a local region through evaporation as compared to how much comes from advection into a region is known as a ``recycling ratio''. The recycling ratio, effectively, denotes the feedback mechanism between the evaporated moisture and precipitation over a region. In addition to this direct feedback mechanism, indirect effects of surface moisture, land.atmosphere exchanges, and turbulent transport on precipitation, which is extracted from the ambient flow, can be diagnosed from moisture budget. In this study, we elucidate the role of soil moisture, parameterizations of surface exchanges, and boundary layers on the diurnal cycle and amounts of precipitation by analyzing moisture budget in regional summer climate simulations over the Rocky Mountains and High Plains.

We also compare simulations using different couplings of surface and boundary layers with common convective closures and explicit microphysics schemes to observations. This allows us to assess their reality. This comparison and the analysis of differences between the simulations allow for quantification of those uncertainties of simulating precipitation in local climates which are due to the incomplete knowledge of surface moisture and inaccuracies in surface and boundary layer parameterizations.

Surface heterogeneity effects on regional-scale fluxes in stable boundary layers: an LES study

Fernando Porte-Angel

(email: fporte@umn.edu)

The ability to parameterize turbulent fluxes over heterogeneous terrain is dependent upon our understanding of the complex, non-linear interactions between land-surface characteristics and atmospheric boundary layer (ABL) dynamics. Under stable ABL conditions, the effect of stratification on local characteristic turbulence length scales further complicates this interaction. In this research, we use large-eddy simulation (LES), with recently developed tuningfree dynamic subgrid-scale models, to study the effect of heterogeneous surface temperature distributions on grid-averaged turbulent fluxes. The simulation setup is based on the GABLS LES intercomparison case with an expanded domain. The surface heterogeneity consists of simple one-dimensional patches with different temperatures. Simulations are performed with changing patch sizes and also temperature differences between patches. Results indicate that within the surface layer both traditional and local Monin-Obukhov similarity theories fail to fully represent the average turbulent fluxes of heat and momentum. The error increases with increasing patch size and also with increasing temperature difference between patches. Above the blending height, which depends on the patch size, the turbulent fluxes follow local similarity. These results are expected to help improve parameterizations used in large-scale weather and climate models. In the future we will extend this research to include the effect of the degree of organization of remotely sensed surface properties on the boundary layer fluxes using data from the NASA CLPX experiment.

The Sensitivity of Peruvian Stratocumulus to Large-Scale Orography

Ingo Richter

Ingo Richter and Carlos R. Mechoso

Dept. Atmospheric and Oceanic Sciences/University of California Los Angeles

(richter@atmos.ucla.edu)

Marine stratocumulus decks play an important role in the climate systems of the tropical Pacific and Atlantic. It is therefore important to understand the processes governing their formation, maintenance and destruction. Even though much progress has been made in this regard, the simulation of these clouds in coupled ocean-atmosphere models remains a difficult problem.

One area of particularly persistent stratocumulus is located off the western coast of South America. The present study examines the sensitivity of those stratocumulus decks to the South American orography. This is done in the context of an uncoupled atmospheric general circulation model capable of producing a realistic simulation of planetary boundary layer (PBL) clouds.

In one set of experiments, the influence of South American orography is investigated. The removal of orography results in a substantial decrease of stratocumulus incidence off the coast of Peru, and the strongest impact is found in austral winter. Inspection of the lower tropospheric stability reveals that it is enhanced when orography is present, which is favorable to stratocumulus formation. The stability increase is due to two effects: 1) colder advection from higher latitudes near the surface, and 2) higher temperatures in the lower troposphere. The first effect results from the blocking of the flow by orography.

The second effect is due to sinking and warming off the Peruvian coast. This mechanism is different from the one found in a companion study of the stratocumulus off the Namibian coast. In that case, the increase in lower tropospheric stability when orography is mediated mostly through horizontal warm air advection above the PBL.

The impact of tropical cyclone remnants on the rainfall of the North American southwest region

Elizabeth A. Ritchie

New Mexico has a mild, arid or semiarid, continental climate characterized by low annual precipitation, abundant sunshine, low relative humidity, and a relatively large annual and diurnal temperature range. Summer rains fall almost entirely during brief, but frequently intense thunderstorms. In general, a southerly circulation from the Gulf of Mexico brings moisture into the State, and strong surface heating combined with orographic lifting as the air moves over higher terrain produce the thunderstorms. The location of the Gulf of Mexico high-pressure system is critically important for location of the monsoonal moisture and summer precipitation in the North American southwest. July, August, and September are the rainiest months over most of New Mexico, producing, on average, approximately 45 percent* of the annual moisture. However, in years where the large-scale pattern is shifted so that the high lies over or to the west of New Mexico, as little as 20% of the annual rainfall has fallen in these months.

An additional source of tropical moisture is occasionally advected into the Southwest U.S. from the Eastern Pacific and Gulf of Mexico in the form of tropical cyclone remnants. These mesoscale systems make landfall on the Mexican, Texan, or Californian coastline and, if the synoptic conditions are favorable, advect over the North American southwest. Although the tropical cyclone-strength winds rapidly diminish upon making landfall, these systems still carry a large quantity of tropical moisture and, upon interaction with mountainous topography, have the potential to drop copious amounts of precipitation. However, these systems are traditionally difficult to forecast accurately due to the nature of their interaction with the midlatitude flow.

In this study we will investigate the impact that tropical cyclone remnants from the Eastern Pacific have on precipitation in the arid North American southwest region. We will study their climatological impact, the resulting rainfall patterns, and the nature of the large-scale circulations that advect them across the southwest U.S. using both observational and model data.

*Value calculated for the National Weather Service (NWS) site at the Albuquerque Sunport.

ECPC Contributions to CEOP

John Roads

(jroads@ucsd.edu)

The Experimental Climate Prediction Center (ECPC) contributed 4 terabytes of model output to the international archive at the Max Planck Institute of Meteorology in Germany. Data from both the Seasonal Forecast Model (SFM, Kanamitsu et al. 2002a) reanalysis and the Reanalysis-2 (RII, Kanamitsu et al. 2002b) are now available over the entire CEOP time period, along with 36-hour forecast experiments from each model initialized daily. We also contributed to the Inter-CSE Transferability Study (ICTS), which compares simulations from different regional models over seven regional domains associated with the eight Continental Scale Experiments (CSEs). For each domain, simulations were carried out from July 1999 to December 2004 with the ECPC Regional Spectral Model (RSM). Output from the regional simulations for the seven domains were also archived at the CEOP model archive. This global and regional output is now being utilized in many CEOP model inter-comparison and in situ validation studies with particular emphasis on the diurnal scale and surface fluxes of water and energy variables and processes.

Ruane and Roads (2006) compared the continental United States summertime diurnal behavior of surface and column-integrated atmospheric water and energy components among three reanalyses. The strength of the diurnal solar forcing leads to consistent phases among surface energy components across the continent and all reanalyses, but the amplitudes vary widely. This forcing has a particularly strong and direct impact on the surface energy cycle, but interacts with many aspects of the surface and columnintegrated water cycle through dynamical convergence, leading to large diurnal fluctuations in the atmospheric reservoir of water vapor. Diurnal variations in atmospheric energy respond not only to the direct solar forcing, but also to the resulting dynamically-forced semidiurnal thermal tide.

Ruane and Roads (2006b) compared the frequency characteristics of three satellites. precipitation products to our output over the 3.5-year CEOP period. The role of the diurnal cycle in different parts of the globe is analyzed using both Fourier and harmonic approaches. By dividing the spectrum of precipitation into three wide bands (covering periods shorter than 2 days, between 2 - 30 days, and longer than 30 days), the frequency contributions reveal that far more power lies in the high-frequency range of the spectrum than is explained by the harmonic fit of the diurnal and semidiurnal cycles. The RII does a much better job of reproducing observed precipitation frequency characteristics at all frequencies than does the SFM, particularly in the Tropics, where the SFM underestimates high-frequency power.

Meinke et al. (2006) evaluated the ECPC RSM simulated precipitation (Meinke et al. 2006). Model deficiencies in the amount of precipitation simulation were identified for almost all model domains. Although the RSM simulates the seasonal evolution and the spatial distribution well, the RSM has an almost uniform positive bias (RSM greater than observations), except for the domain over the BALTic sea EXperiment (BALTEX) CSE, where the RSM has a negative bias. Most of the positive bias is either connected with the Intertropical Convergence Zone (ITCZ) convection or with monsoon convection (Southeast Asia). Stratiform precipitation is also excessive over high orography. Since the control simulations used the Relaxed Arakawa Schubert scheme (RAS), sensitivity tests with 3 additional convection schemes were then carried out to see if the simulations could be improved. The additional convection schemes included: 1) the Simplified Arakawa Schubert scheme (SAS), 2) the Kain-Fritsch (KF), and 3) the Zhang McFarlane (ZM). It was found that the precipitation simulation could be significantly improved for for almost all domains using the SAS scheme. To provide the best possible data for the ICTS, new long-term runs for the seven domains have been started using SAS.

Kanamitsu, M., A. Kumar, H.-M. H. Juang, W. Wang, F. Yang, J. Schemm, S.-Y. Hong, P. Peng, W. Chen and M. Ji, 2002a: NCEP Dynamical Seasonal Forecast System 2000. Bull. Amer. Met. Soc., 83, 1019-1037

Kanamitsu, M., E. Wesley, J. Woollen, S. -K. Yang, J. J. Hnilo, M. Fiorino, and G. L. Potter, 2002b: NCEP-DOE AMIP-II reanalysis (R-2). Bull. Amer. Meteor. Soc. 83, 1631-1643

Meinke, I, Roads, J and M. Kanamitsu, 2006: Global evaluation of the RSM simulated precipitation through transferability studies during CEOP. Submitted to JMSJ, CEOP special issue (January 2006).

Ruane, A.C., and J.O. Roads, 2006a: .The diurnal cycle of water and energy over the Continental United States from three reanalyses.. Submitted to JMSJ, CEOP special issue (January 2006).

Ruane, A.C., and J.O. Roads, 2006b: Low, synoptic and high frequency characteristics of precipitation in observations and two CEOP analyses. (To be submitted)

Moisture parameters in models and the regional reanlaysis

David Salstein

We analyzed a number of parameters including evaporation, precipitation, water vapor fluxes and divergence, and precipitable water for the warm seasons (May - Oct) of some focus years highlighted for studies of areas including the North American Monsoon Region over the southwest US/ Mexico region. Various regional models that participated in the first modeling and analysis efforts were identified, and budget differences were identified, as well as a comparison with the parameters derived in the North American Regional Reanalysis (NARR). The NARR was used as well to note the characteristics of the recent year, and will be used too to compare model results for 2004 when they become available.

Diagnostic and Numerical Studies with SALLJEX data from diurnal to intra-seasonal time scales

Celeste Saulo

(saulo@cima.fcen.uba.ar)

The focus of this research is in the interaction of diurnal, synoptic and intra-seasonal time scales with a main theme on low level circulations, the veracity of their representation in analyses - with and without enhanced SALLJEX data- and forecast simulations, land surface effects and circulation impact and feedbacks with downstream rainfall predictability.

Recently, a global reanalysis using SALLJEX (South American Low Level Jet Experiment) observations has been completed and it is now available (Herdies et al., 2006 submitted). Preliminary results indicate that enhanced observations over central South America have an impact not only locally but also remotely (as shown by the 500 hPa meridional wind component). Additional examination of these data sets to better understand this behavior is in process. The impact of SALLJEX observations upon forecast quality is being addressed through a set of numerical experiments using WRF (Weather Research and Forecasting) model initialized with GDAS and with SALLJEXgridded reanalysis. Results for individual cases, mostly related with heavy precipitation over Southeastern South America show some impact in precipitation and low level circulation representation.

In order to investigate land/ atmosphere interactions over Central Argentina and Southeastern South America, several sensitivity studies using WRF model and employing different land use and soil moisture patterns are being done. A case study of a Northwestern Argentina Low episode observed during SALLJEX reveals a strong sensitivity to an augmentation of soil dryness over western Argentina, which causes a deepening of the NAL and an acceleration of the northerly flow to the east of the NAL. This kind of response, as expected, leads to a change in the position of the related precipitation area that shifts from central La Plata Basin (LPB) to southern LPB.

National Weather Service Hydrologic Ensemble Pre-Processor (EPP) GFS Subsystem

J. Schaake, R. Hartman, J. Demargne, L. Wu, M. Mullusky, E. Welles, H. Herr, D. J. Seo, and P. Restrepo

This poster reports on the progress being made to develop an Ensemble Pre-Processing (EPP) system that will produce ensemble precipitation and temperature forcing for Ensemble Streamflow Prediction (ESP) at National Weather Service River Forecast Centers for forecast lead times from one day to one year. The goal is to remove biases from input weather and climate forecasts and to downscale the information to the scales required by hydrologic forecast models. Because hydrologic models are highly non-linear, it is essential for the EPP to reliably preserve uncertainty information at multiple space and time scales over all forecast lead times. The development strategy is to introduce a set of simple, parsimonious procedures that provide an initial .reference. capability. We plan to add additional procedures based on results of CPPA research and results from HEPEX testbeds.

Drought and wet spells over the United States and Mexico

Jae Schemm

The wet and dry extreme events as measured by the Palmer Drought Severity Index (PDSI) and the Standardized Precipitation Index (SPI) have preferred regions to occur and persist. The interior United States west of 90-95W and the northwestern Mexico are more prone to droughts and wet spells. On contrary, the extreme events are less persistent over the eastern United States and California. The physical mechanisms for the regional preference are examined by classifying extreme events into three categories: Multi-decadal, interannual and intraseasonal time scales.

The extreme events are most likely to occur over the northwestern Mexico and the western Mountain regions. Rainfall over these two regions is associated with multi-decadal modes of SSTAs. The extreme events which have interannual time scales are located over the Great Plains and Arizona and western New Mexico. The SST forcing which persists over the raining season has consistent influence on rainfall over these areas.

The areas that the extreme events are less likely to occur and persist are the central eastern United States, the East Coast and the Ohio Valley. These areas have very weak seasonal cycle. Rainfall from many seasons can contribute to the SPI or the PDSI. Rainfall is influenced by ENSO events which often last from winter to summer. However, ENSO often has the opposite impact on winter and spring or summer rainfall.

The extreme events are also less persistent over California because rainfall is modulated by not only ENSO but also convection over the East Pacific and the intraseasonal oscillations which have the time scales less than a season.

NAME CPT Project - Issues for Warm Season Prediction

Jae Schemm

Co-Authors:

J. Schemm, K. Mo, L. Williams and S. Yoo , NOAA/NWS/NCEP/CPC D. Gutzler, Univ. of New Mexico

NAME Climate Process and Modeling Team (CPT) has been established to address the need of linking climate process research to model development and testing activities for warm season climate prediction. The project builds on two existing NAME-related modeling efforts. One major component of this project is the organization and implementation of a second phase of NAMAP, based on the 2004 season. NAMAP2 will re-examine the metrics proposed by NAMAP, extend the NAMAP analysis to transient variability, exploit the extensive observational database provided by NAME 2004 to analyze simulation targets of special interest, and expand participation. Vertical column analysis will bring local NAME observations and model outputs together in a context where key physical processes in the models can be evaluated and improved.

The second component builds on the current NAME-related modeling effort focused on the diurnal cycle of precipitation in several global models, including those implemented at NCEP, NASA and GFDL. Our activities will focus on the ability of the operational NCEP Global Forecast System (GFS) to simulate the diurnal and seasonal evolution of warm season precipitation during the NAME 2004 EOP, and on changes to the treatment of deep convection in the complicated terrain of the NAMS domain that are necessary to improve the simulations, and ultimately predictions of warm season precipitation These activities will be strongly tied to NAMAP2 to ensure technology transfer from research to operations.

Results based on experiments conducted with the NCEP GFS GCM will be reported at the meeting with emphasis on the impact of horizontal resolution in predicting warm season precipitation over North America.

Progress Update on Development of Prototype Hydrologic Ensemble Forecast System for NWS Operations

Dong-Jun Seo

NOAA/NWS/Office of Hydrol. Development & Univ. Corp. for Atm. Res.

dongjun.seo@noaa.gov

Co-Authors:

Julie Demargne

NOAA/NWS/Office of Hydrol. Development & Univ. Corp. for Atm. Res.

julie.demargne@noaa.gov

Shuzheng Cong

NOAA/NWS/Office of Hydrol. Development & Univ. Corp. for Atm. Res.

shuzheng.cong@noaa.gov

Limin Wu

NOAA/NWS/ Office of Hydrol. Development & RS Information Systems

limin.wu@noaa.gov

John Schaake

NOAA/NWS/ Office of Hydrol. Development, Consultant

john.schaake@noaa.gov

Pedro Restrepo

NOAA/NWS/ Office of Hydrol. Development

pedro.restrepo@noaa.gov

As a part of the CPPA Core Project, NOAA/NWS/OHD with RFCs and other collaborators has been developing a prototype hydrologic ensemble forecast system for experimental operation at RFCs. Leveraging the NOAA.s Advanced Hydrologic Prediction Service (AHPS) program, this activity fast-tracks research, development, and research-to-operations transition of hydrologic ensemble prediction and data assimilation capabilities for NWS operations. In this poster, we provide an overview of the OHD-led development activities and an update on the progress. In the two companion posters, we describe two of the prototype components of the forecast system: the Ensemble Pre-Processor (EPP), which generates bias-adjusted (in the probabilistic sense) ensembles of precipitation and temperature from single-value forecasts, and the prototype data assimilator of hydrologic and hydrometeorological observations for operational lumped and distributed hydrologic models.

Real-time Assimilation of Streamflow Data into Operational Hydrologic Models

Dong-Jun Seo

NOAA/NWS/ Office of Hydrol. Development & Univ. Corp. for Atm. Res.

dongjun.seo@noaa.gov

Co-Authors:

Victor Koren

NOAA/NWS/ Office of Hydrol. Development

victor.koren@noaa.gov

Lee Cajina

NOAA/NWS/ Office of Hydrol. Development

lee.cajina@noaa.gov

Robert Corby

NOAA/NWS/West Gulf River Forecast Center

robert.corby@noaa.gov

Tracy Howieson

NOAA/NWS/West Gulf River Forecast Center

tracy.howieson@noaa.gov

Uncertainty in the initial conditions of soil moisture accounting models is one of the largest sources of error in operational hydrologic prediction. Being an integrated quantity in space and time, streamflow observations provide, measurement by measurement, arguably the most reliable piece of information about the aggregate state of the hydrologic system. Assimilating streamflow data into soil moisture accounting models, however, is challenging because of large degrees of freedom involved, and nonlinear model dynamics and observation processes. In this poster, we present the results from a real-time experiment at WGRFC in Forth Worth, TX, carried out to evaluate a variational data assimilator (DA) for the Sacramento soil moisture accounting model (SAC), and share preliminary results from a hindcasting experiment carried out to evaluate a variational DA for a prototype OHD/Hydrology Laboratory Distributed Hydrologic Model (HL-DHM).

The Impact of the NAME Simple Raingauge Network Data on the CPC Precipitation Analysis Quality

Wei Shi

The raingauge data collected from the CPPA funded project Enhancement of the Daily Raingauge Network in Mexico in Support of NAME has been incorporated into CPC.s existing US_Mexico raingauge database for the period of 2004-present. The daily precipitation analysis based on this new database is compared to CPC.s existing real-time analyses for the same period to investigate the impact of the new data. Intercomparisons of daily, monthly and seasonal precipitation statistics between the analyses, and comparisons of each analysis to a suite of satellite estimates of precipitation provide an assessment of the range of uncertainty in our precipitation analysis products.

Ensemble Inference and Performance Assessment of Hydrologic Prediction in the Presence of Various Uncertainty Sources

S. Sorooshian

The key step to enhance the accuracy of hydrologic prediction is the realistic characterization of uncertainty. In this study we use a sequential ensemble filtering method to propagate the uncertainties of forcing data in the Leaf River basin in Mississippi, into a conceptual hydrologic model and quantify the joint state-parameter and streamflow forecasting uncertainties. Recent progress in satellite-based precipitation observation techniques offers an attractive option for considering spatio-temporal variation of precipitation as particularly needed in ungauged basins. In this study we use the PERSIANNCCS precipitation product and characterize its uncertainty by a power law function of precipitation intensity as well as its spatio-temporal scale. Some uncertainty scenarios are set up to incorporate and investigate the impact of the individual uncertainty sources from precipitation, parameters and also combined error sources on the hydrologic response. Also probabilistic measures are used to quantify the quality of ensemble prediction.

Analysis of NARR, LDAS and LIS Surface Water and Energy Balance for Water Resources Applications

Daivd Toll

The primary objective of our study is to evaluate surface water and energy balance for water resources applications through study of a selected range of modeling and data assimilation systems associated with NASA and NOAA. Specifically, the joint analysis of North American Regional Reanalysis (NARR) data, North American Land Data Assimilation System (NLDAS) and Land Information System (LIS) data versus in-situ measurements provides a unique look at the water and energy flux estimation from different modeling and data system approaches. For reference we used in situ data from the Coordinated Enhanced Observing Periods (CEOP 3&4), the Oklahoma Mesonet sites, and the NASA-Reclamation ET tower sites.

Comparison shows that large biases are found on partitioning sensible heat and latent heat fluxes in most models during spring and summer seasons. . Possible factors, such as model forcing, land cover classifications and model physics, affecting the energy fluxes are further investigated at a spatial high resolution through NASA LIS. It was found that the model forcing data, land cover classifications and model physics had significant influences on the energy flux estimation. This study will suggest the optimal forcing data and modeling for future operational predictions.

Impact of the Atlantic Warm Pool on the Summer Climate of the Western Hemisphere

Chunzai Wang

The North Atlantic subtropical high (NASH), being the strongest during the summer, determines the strength of the tropical easterly trade winds at its southern flank. The easterly trade winds carry moisture from the tropical North Atlantic into the Caribbean Sea where the flow intensifies forming the Caribbean low-level jet (CLLJ). The CLLJ then splits into two branches: one turning northward and connecting with the Great Plains low-level jet (GPLLJ), and the other one continuing westward across Central America into the eastern North Pacific. This paper finds that the easterly CLLJ is maximized in the summer and winter, whereas it is minimized in the fall and spring. The semiannual feature of the CLLJ results from the semi-annual variation of sea level pressure in the Caribbean region owing to the westward extensions and eastward retreats of the NASH.

The Atlantic warm pool (AWP) with a large area of warm water is comprised of the Gulf of Mexico, the Caribbean Sea, and the western tropical North Atlantic. The NCAR community atmospheric model and observational data are used to investigate the impact of the AWP on the summer climate of the Western Hemisphere. Two groups of the model ensemble runs with and without the AWP are performed and compared. The model results show that the AWP.s effect is to weaken the summertime NASH, especially at its southwestern edge. The AWP also strengthens the summertime continental low over the North American monsoon region. In response to these pressure changes, the CLLJ is weakened and the GPLLJ is strengthened during the summer. The weakening of the CLLJ decreases the westward moisture transport from the AWP and thus suppresses rainfall in the eastern North Pacific, whereas the strengthening of the GPLLJ enhances the northward moisture transport for summer rainfall over the central United States. Finally, the AWP largely reduces the tropospheric vertical wind shear in the main development region that favors the hurricanes. formation and development during August-October.

Quantifying the strength of soil moisture-precipitation coupling and its sensitivity to changes in surface water budget

Guiling Wang

Guiling Wang, Yeonjoo Kim, Dagang Wang

Department of Civil & Environmental Engineering

University of Connecticut

Correspondence: GuilingWang@uconn.edu

This paper presents a new index to quantify the strength of soil moistureprecipitation coupling in AGCMs based on intra-ensemble relative variance, and explores how the soil moisture-precipitation coupling in the CAM3-CLM3 model responds to a modification in the vegetation canopy interception parameterization that leads to significant surface water budget changes. Specifically, this study examines how these surface water budget changes influence (a) the strength of soil moisture-precipitation coupling as measured by the proposed new index, (b) the strength of soil moisture-precipitation coupling as measured by the index currently used in the Global Land-Atmosphere Coupling Experiment (GLACE), and (c) the memory of the coupled land-atmosphere system as measured by the correlation between soil moisture and subsequent precipitation and evapotranspiration. Two main differences are found between the newly proposed index and the index currently used in GLACE. First, the newly proposed index identifies Europe as a major region of modest-to-strong coupling in addition to what the GLACE index suggests. Secondly, as a result of the canopy interception parameterization changes that presumably favor a stronger soil moistureprecipitation coupling, the newly proposed index increases significantly but the GLACE index decreases in some major regions of strong coupling. Changes in the land-atmosphere system memory suggest an increase of coupling strength, consistent with results based on the proposed index. An excessive dependence of the GLACE index on the relative importance of atmospheric internal variability is identified as an important cause for the differences between the new index and the GLACE index in the regions of strong coupling they identify and in their response to model parameterization changes.

Impact of vegetation feedback on the response of precipitation to antecedent soil moisture anomalies over North America

Guiling Wang

To investigate how vegetation feedback modifies the impact of initial soil moisture anomalies on the subsequent precipitation over North America, a series of ensemble simulations are carried out with the coupled CAM-CLM model. The CLM model includes a predictive vegetation phenology scheme so that the coupled model can represent interactions between soil moisture, vegetation and precipitation at the seasonal timescale. The focus of this study is on how vegetation feedback varies with the timing and direction of initial soil moisture anomalies. During summer, wet soil moisture anomalies lead to increased vegetation growth, and the resulting vegetation anomalies enhance the response of precipitation to the initial soil wetness via increased evapotranspiration and surface heating. Therefore, the soil moisture-vegetation-precipitation feedback is positive under wet summer soil moisture anomalies. The response of vegetation to dry soil moisture anomalies in the summer months, however, is not significant due to a dry bias in the model, so the resulting vegetation feedback on precipitation is minimal. To soil moisture anomalies in spring, vegetation shows delayed response since vegetation growth is limited by both cold temperature and water availability in that time of the year. During the summer following spring soil moisture anomalies, vegetation feedback is negative, i.e., it tends to suppress the response of precipitation.

Towards the improvement of the NCEP Noah land surface model in the North American Land Data Assimilation System during the warm season

Helin Wei

Environmental Model Center, NOAA/NWS/NCEP

(helin.wei@noaa.gov)

Co-Authors:

Kenneth Mitchell, Environmental Model Center, NOAA/NWS/NCEP

Michael EK, Environmental Model Center, NOAA/NWS/NCEP

Youlong Xia, Environmental Model Center, NOAA/NWS/NCEP

The NCEP Noah land surface model (LSM) has been extensively evaluated with in situ observations over the southern Great Plains during the North American Land Data Assimilation System (NLDAS) Phase I simulation periods (May - September of 1998 and 1999). The model does a fairly good job but still some discrepancies in the surface energy partition between model and observations. The Bowen ratio is too low in the spring and too high in the summer. To improve the performance, we have further refined some parameters particularly those related to the calculation of canopy resistance such as the soil moisture stress function, vapor pressure deficit function, and minimum canopy resistance values. Varied LAI and root fraction have been applied as well to reflect its seasonal variation which has significant consequence on the temporal evolution of surface fluxes.

The new version of Noah LSM has been used to rerun NLDAS Phase I 3- year core period as well as some sensitivity tests. These results have been validated against some observation data. It is found that the high/low latent heat flux biases during the spring/summer have been reduced in the new version. Also the surface skin temperature and the surface water budget have been improved significantly.

Oceanic Eddy Flux Forcing in the Eastern Subtropical Pacific

Robert Weller

A surface flux buoy moored under the Chile-Peru stratus decks shows that a significant contribution to the annual mean heat flux is made by the divergence of the mesoscale oceanic eddy flux. Eddies formed near the coast, and composed of upwelled water, propagate into the interior and decay. The mixing of this coastal upwelled water with the subtropical surface layers represents an order one source of cooling and freshening. The physical processes that create this large heat and freshwater flux are germane to most eastern boundary regions.

University of Washington West-wide experimental hydrologic forecast system

Andrew W. Wood and Dennis P. Lettenmaier

We describe an implementation of macroscale land surface models over the western U.S. at 1/8 degree spatial resolution for experimental hydrologic prediction at lead times of up to one year using the Variable Infiltration Capacity (VIC) model. Climate forecast ensembles are downscaled from NCEP and NASA climate model ensemble output (monthly temperature and precipitation), and from the CPC official seasonal outlooks. As a benchmark forecast, we also produce parallel forecasts using VIC via the well-known Extended Streamflow Prediction (ESP) method, and the ESP forecasts are further composited to provide ENSO and PDO-conditioned ensembles. The primary forecast products are: 1) monthly streamflow distributions and volume runoff statistics (similar to those provided by the NWS River Forecast Centers) for about 100 locations in the western US; 2) diagnostics of related climate and water balance variables (soil moisture and snow water equivalent or SWE) during the water year up to the forecast date; and 3) spatial maps for the entire domain of forecast ensemble averages for runoff, soil moisture, and SWE. Initial testing in real-time began with bi- monthly updates for the Pacific Northwest (for winter 2002-3), and the domain was subsequently expanded to the U.S. west of the Rocky Mountains. Initial hydrologic conditions are improved using a simple method for assimilating observed snow water equivalent anomalies at the start of the forecast. We have also addressed the relative dearth of meteorological observations in the final months before the forecast start using interpolated monthly precipitation percentiles and temperature anomalies from a set of real-time index stations. We are in the process of increasing the forecast update cycle to weekly, and expanding the forecast domain to include the upper Missouri River basin. This poster gives an overview of the components of the system and the ongoing developmental activities.

Launching Phase II of NLDAS: A Preliminary Result

Dr. Youlong Xia

NOAA/NWS/NCEP/EMC

Youlong.Xia@noaa.gov

Kenneth Mitchell, NOAA/NWS/NCEP/EMC

Eric Wood, Princeton University

Dennis Lettenmaier, University of Washington

Lifeng Luo, Princeton University

Andrew Wood, University of Washington

Helin Wei, NOAA/NWS/NCEP/EMC

Brian Cosgrove, NASA/GSFC/HSB

Christa Peters-Lidard, NASA/GSFC/HSB

John Schaake, NOAA/NWS/OHD

Pedro Restrepo, NOAA/NWS/OHD

The North American Land Data Assimilation System (NLDAS) is multiinstitutional and multi-models research project in an uncoupled mode. Its purpose is (1) to improve weather and seasonal climate prediction in the North America through providing reliable initial states, such as soil moisture, soil temperature, snowpack, and other reliable parameters such as albeo to regional weather and climate models, and (2) to provide water information (soil moisture, snowpack, runoff, streamflow) to government agencies for water resource management and uses such as drought monitoring, agricultural management, flood prediction etc. Phase I of the NLDAS project included a 3-year retrospective land data assimilation analysis by running four land surface models (NOAH, VIC, MOSAIC, SAC) using 3-year retrospective forcing data spanning October 1996 through September 1999, and a realtime land data assimilation analysis spanning April 1999 to present with one land model (Noah).

Phase II of the NLDAS has been launched recently via collaborations between NCEP/EMC, NWS/OHD, NASA/GSFC/HSB, NCEP/CPC, Princeton University, University of Washington, University of Maryland, and the other research institutions. It will include 1) a long-term 25-30 year NLDAS retrospective analysis using observed precipitation from CPC precipitation analysis and all other surface forcing form North American Regional Analysis (NARR), 2) a daily realtime update and 3) a seasonal predictive component. This seasonal predictive component consists of multi-model ensemble seasonal dynamical prediction products from global climate models, empirical seasonal prediction products from the CPC seasonal outlook, prediction from land surface models, and Bayes theory to use to weight different sources of predicted surface forcing. Here a preliminary result is given only. For long-term retrospective analysis, a 9-year land water and energy balance analysis was conducted using the NOAH model and a NLDAS dataset from October 1996 to June 2006. The results are employed to analyze temporal and spatial distributions for soil moisture, soil temperature, sensible heat flux, latent heat flux, and skin temperature and are compared with observations. In the near future, the other 3 land models will be run (VIC, MOSAIC, SAC). For the seasonal prediction component, we transition to and demonstrate of NCEP the VIC-based ensemble seasonal streamflow prediction system developed under CPPA-sponsorship at Princeton University using ensemble seasonal forecasts of surface forcing from NCEP's Climate Forecast System (CFS). In the near future, we will transition to NCEP the methodology of the CPPA-sponsored development at University of Washington, whereby the official seasonal forecasts of CPC are applied to generate additional ensemble member of seasonal predictions of land surface forcing for the purpose of deriving multiple land models. The multi-models and multi-ensembles seasonal streamflow prediction system using multi-models (including dynamical and empirical models) and multi-ensemble seasonal predictions products will be installed in the future.

Assessing the NCEP CFS Model Bias Associated with the Marine Stratus Clouds over Southeastern Pacific

Pingping Xie1), Wanqui Wang1), Wayne Higgins1), M. Cronin2), P.A. Arkin3), R. Weller4)

1) NOAA Climate Prediction Center

2) NOAA Pacific Marine Environmental Laboratory (PMEL)

3) ESSIC, Univ. of Maryland

4) Woods Hole Oceanographic Institution

A preliminary investigation has been conducted to examine the bias in the NCEP operational CFS climate forecast model associated with the insufficiently simulated stratus clouds over SE Pacific. Global fields of SST, surface winds, solar radiation, cloudiness, and precipitation generated by fully-coupled and radiation-corrected CFS simulations have been compared with in situ and satellite observations. Our initial results showed the following:

1) While large-scale precipitation patterns are reproduced reasonably by the CFS CMIP simulations, differences exist in the magnitude of precipitation and in the latitudinal position of the ITCZ over the eastern Pacific sector;

2) The latitudinal displacement of the ITCZ in the CFS CMIP run is closely related to the warm SST bias in SE Pacific stratus deck region;

3) About half of the warm SST bias is attributable to the insufficient amount of stratus clouds simulated by the CFS model (and most other climate models as well);

4) The interannual variability in SST over the central weakens with the reduction in the warm SST bias in the eastern Pacific, and

5) The stratus clouds over the regions have very low cloud tops and exhibit a strong diurnal cycle generated by a regional circulation caused by the contrasting surface conditions between the oceanic regions and their adjacent continents.

Further work is underway to examine the relative importance of the convection over the land areas in forming the stratus clouds and the oceanic processes in forming the warm SST bias. Results will be reported at the workshop.

A Regional Ocean-Atmosphere Model for Eastern Pacific Climate: Towards Reducing Tropical Biases

Shang-Ping Xie

The tropical Pacific Ocean is a climatically important region, home to El Nino and the Southern Oscillation. The simulation of its climate remains a challenge for global coupled ocean-atmosphere models, which suffer large biases especially in reproducing the observed meridional asymmetry across the equator in sea surface temperature (SST) and rainfall. A basin ocean general circulation model is coupled with a full-physics regional atmospheric model to study eastern Pacific climate processes. The regional ocean-atmosphere model (ROAM) reproduces salient features of eastern Pacific climate, including a northward-displaced intertropical convergence zone (ITCZ) collocated with a zonal band of high SST, a low-cloud deck in the southeastern tropical Pacific, the equatorial cold tongue and its annual cycle. The simulated low-cloud deck experiences significant seasonal variations in vertical structure and cloudiness; cloud becomes decoupled and separated from the surface mixed layer by a stable layer in March when the ocean warms up, leading to a reduction in cloudiness. The interaction of low cloud and SST is an important internal feedback for the climatic asymmetry between the Northern and Southern Hemispheres. In an experiment where the cloud-radiative effect is turned off, this climatic asymmetry weakens substantially, with the ITCZ migrating back and forth across the equator following the sun. In another experiment where tropical North Atlantic SST is lowered by 2^oC.say, in response to a slow-down of the Atlantic thermohaline circulation as during the Younger Dryas.the equatorial Pacific SST decreases by up to 3^oC in January-April but changes much less in other seasons, resulting in a weakened equatorial annual cycle. The relatively high resolution (0.5^o) of the ROAM enables it to capture mesoscale features such as tropical instability waves, central American gap winds, and a thermocline dome off Costa Rica. The implications for tropical biases and paleoclimate research are discussed.

The effect of vegetation biophysical processes (VBP) in climate simulation

Y. Xue

The study (Xue et al., 2004, 2006) has shown that using the NCEP general circulation model (GCM) coupled with two different land surface schemes, one with the Simplified Simple Biosphere Model (SSiB) and another with a two layer soil model, two simulations produce substantial different monsoon evolution, large scale circulation, and precipitation at continental scales, especially in the monsoon regions and some of the large continental areas.

To further understand the VBP effect, we conduct two sets of 6-year simulation using the UCLA GCM with climatological sea surface temperature (SST) and two land surface parameterizations. one is SSiB-1 (referred to as UCLA GCM/SSiB-1) and another is the standard UCLA land surface parameterizations (referred to as UCLA GCM/CTL): specified soil moisture and surface albedo, i.e., no interaction is allowed. Meanwhile, the surface temperature is obtained using a simple single layer energy balance model. The UCLA/SSiB-1 substantially reduces the bias and root-mean-square (RMS) errors in the UCLA GCM/CTL precipitation simulation. Over the land, the annual mean bias was reduced by 69% and RMS error was reduced by 40%. This improvement is very consistent for every season/month (Table 1). Over the ocean, there is no substantial difference between the UCLA GCM/CTL and the UCLA GCM/SSiB-1. The improvement is very significant during the northern monsoon onset (Figs. 1a and 1b). The UCLA/SSiB eliminates wide spread wet bias over the North American continent, Eurasian continent, and the Sahel area in May. This improvement is consistently throughout the northern summer monsoon season (Figs. 2a and 2b). During the southern monsoon season, the UCLA GCM/SSiB-1 also improves the monsoon simulation (Figs 3a and 3b), although it is not as substantial as the northern summer, mainly due to the land mass size. Most improvement is in southern and central African continent, Amazon, and eastern Australia.

To further test the VBP effect, we also run the UCLA/SSiB-2 for 6-years. SSiB-2 includes Collatz et al..s photosynthesis model. To improve computational efficiency and to produce stable solutions for long-term simulations in GCM, quasi-analytical solutions of photosynthesis parameterizations have been developed. Meanwhile, a new scaling methodology for the canopy scale, which includes leaf-shading effects, has been developed to improved simulation of the diurnal cycle of carbon and evapotranspiration. Although the UCLA GCM/SSiB-2 produces the similar global annual mean precipitation as the UCLA/SSiB-1, it improves some seasonal mean precipitation (Table 1). Over the North American and Eurasian boreal forest areas, the improvement in precipitation is quite substantial in the northern summer season (Fig. 1c and Fig. 2c).

Summer and Winter Seasonal Ensemble Hindcasts over North American with the Eta Regional Climate Model

Rongqian Yang and Kenneth Mitchell

SAIC and NOAA/NWS/NCEP, Camp Springs, MD, Rongqian.Yang@noaa.gov;

NOAA/NWS/NCEP, Camp Springs, MD, Kenneth.Mitchell@noaa.gov

To examine actual seasonal prediction using a regional climate model (RCM), in this study we continue our advancement and testing of a high resolution Eta-model based Regional Climate Model (Eta RCM). In terms of physics, resolution (32-km) and domain size (large North and Central American domain), the version of the Eta model we use is identical to that used by NCEP in the Eta-model based N. American Regional Reanalysis (NARR). We only make changes to model configuration to make the model execution consistent with the longer time scales of seasonal forecasts. These configuration changes include adding daily updates to the SST fields, sea ice cover, green vegetation cover, and surface albedo.

The substantial extension here with respect to our previously presented Eta RCM studies is that we executed a complete 5-year hindcast of Eta RCM seasonal predictions for the period 2000-2004, plus the two additional years of 1983 and 1999, for both summer and winter prediction scenarios. In contrast to many previous RCM studies, in which the RCM is initialized from one single date, we used an ensemble approach in both simulation mode and fully predictive mode. In the classical simulation mode, we apply observed SST and analyzed lateral boundary conditions, in our case from NCEP Global Reanalysis II. In the full prediction mode, we apply the predicted SSTs and predicted lateral boundary conditions from NCEP's Climate Forecast System (CFS). Our full prediction mode study here is one of only a handful of previous RCM studies carried out in full prediction mode. The vast majority of previous RCM studies have been for either the simulation mode or the "quasi-prediction" mode (which uses predicted lateral boundary conditions but observed SSTs).

For the summer season predictions and simulations, we produced an ensemble of ten Eta RCM runs out to end of September from ten different initial dates spanning mid April through early May for each summer for each year of 2000-2004 and 1999. We focus on the Eta RCM and CFS summer prediction for year 1999, in which a rather above normal (wet) southwest U.S. monsoon event occurred. For the winter season predictions and simulations, we produced an ensemble of seven Eta RCM runs out to end of April from seven different initial dates spanning mid December to late December, for each winter of 2000-2004 and 1983. We focus on the Eta RCM and CFS winter prediction for year 1983, in which a rather strong El' Nino event occurred.

Our focus in this study is to what extent the Eta RCM prediction of seasonal precipitation does or does not show improved skill or value-added attributes (such as temporal frequency) relative to the driving ensemble predictions of the CFS global model. The advantage of investing the great effort to execute a multi-year hindcast, such as the 5-year hindcast here for 2000-2004, is that model predictions can be cast in terms of predictions of anomalies with respect to the model's own climatology, thereby mitigating the effects of model systematic errors and biases.

The Sensitivity of North American Monsoon System Precipitation to Vegetation and Groundwater Dynamics

Zong-Liang Yang

Department of Geological Sciences

The John A. and Katherine G. Jackson School of Geosciences

The University of Texas at Austin, Austin, Texas

liang@mail.utexas.edu

Co-authors:

Guo-Yue Niu, and Xiao-Yan Jiang

Department of Geological Sciences

The John A. and Katherine G. Jackson School of Geosciences

The University of Texas at Austin, Austin, Texas

This study explores the effects of vegetation and groundwater dynamics on the precipitation during the North American monsoon season through sensitivity studies by using a coupled land-atmosphere model, the Weather Research and Forecasting (WRF) model with the Noah land surface model (LSM). A dynamic vegetation model and a simple groundwater model (SIMGM) are implemented into the unified Noah LSM. Three sensitivity experiments are conducted with time-varying sea surface temperatures: 1) the vegetation fraction is prescribed according to the value on the initial time of the model integration ; 2) vegetation dynamics as represented by the dynamic vegetation model in the Noah LSM; and 3) based on 2) but with groundwater dynamics as represented by the SIMGM.

Results show that the inclusion of the dynamic vegetation improves the July precipitation in the Northern North American Monsoon System (NNAMS) region. The simulation is further improved with the SIMGM in the Noah LSM and more peak precipitation in the NNAMS and Southern Great Plains are captured. The default WRF/ Noah LSM produces much less precipitation in the NNAMS and the Central U.S. The increased precipitation simulated by the experiments 1) and 2) agrees well with the increase of vegetation fraction. In addition, the implementation of the SIMGM induces higher latent heat flux in the Central U.S. and the NNAMS, resulting in more precipitation. These sensitivity experiments demonstrate the need for augmented representations of vegetation and groundwater dynamics in the current Noah LSM.

Hydroclimatic Anomaly Propagation with Increasing Depth of the Soil Profile in Illinois - Implications for Land Memory Processes

Pat Yeh

In this study we investigate the patterns of hydroclimatic Anomalies (drought and flood) at the regional scale of Illinois, based on a comprehensive data set covering 25-year (1981-2005) monthly precipitation, soil moisture, groundwater depth, and streamflow. The focus is on the vertical (downward) propagation of hydroclimatic anomalies with increasing soil depths as well as the associated anomaly amplification or dissipation, at the monthly, seasonal, and inter-annual timescales. The characteristics of persistence and downward propagation of droughts and floods through the soil profile and unconfined aquifer are analyzed by using analytical crossing theory. Crossing theory deals with the properties of excursions of random processes above and below certain threshold values, and is well suited for studying droughts and floods. The role of deep-layer soil moisture and shallow groundwater in affecting land surfaceatmospheric feedback on longer timescales is underscored.

Growing temperate shrubs over arid to semi-arid regions in CLM-DGVM

Xiaodong Zeng and Xubin Zeng

Shrubs, especially the temperate shrubs, distribute widely in the world and covers more than 10% of the land. They are the dominant vegetations over the semi-arid regions. Currently released CLM-DGVM has not yet included shrubs. This study is to develop a new component for the CLM-DGVM to realistically grow shrubs over semiarid regions. The major model revisions and improvements include: (1) a new function describing shrubï.2s ability of maintaining its photosynthesis under the stress of drought; (2) a new phenology type describing the quickly response of shrub to rain event; (3) a set of parameters for shrub morphology; (4) a new scheme for the light competition among trees-grasses-shrubs. Results show that our revision can grow shrubs and reproduce the phenomenon of competition and coexistence of shrub and grass in the arid to semiarid regions.