GCIP has evolved from its beginning as largely an international project to a largely national project with participation from many different agencies in the USA. This evolution has fostered the development of cooperative and collaborative activities in many different areas.

8.1 Collaboration with Other GEWEX Projects

The GCIP applied research project has connectivity to GEWEX as a whole and to its components through a commonality of scientific objectives. For example the Project for the Intercomparison of Land-Surface Parameterizartion Schemes (PILPS) is partially supported by the NOAA/OGP GCIP Program. The mesoscale convective cloud modeling tasks are coordinated with the theoretical and observational tasks of the GEWEX Cloud Systems Study, and surface flux studies and modeling of the atmospheric planetary boundary-layer research will be carried out in close collaboration with ISLSCP.

During 1995, GCIP and other similar continental-scale projects were combined under a Hydrometeorology Panel within GEWEX. The principal research task for this panel is to assist GEWEX in demonstrating skill in predicting changes in water resources and soil moisture on time scales up to seasonal and annual as an integral part of the climate system. GCIP will benefit from this coordination of continental-scale experiments. The results of the Canadian Mackenzie GEWEX Study (MAGS) will contribute to an improved understanding of cold-region, high-latitude hydrological and meteorological processes, and the role they play in the global climate system. An essential goal of the GEWEX Asian Monsoon Experiment (GAME) is to understand the physical basis of the seasonal forecast of the Asian monsoon and to improve the modeling techniques related to predicting and assessing the regional hydrometeorological conditions under anthropogenic as well as natural climate changes. The key scientific issues in the Baltic Sea Experiment (BALTEX) relate to coupling between the atmosphere and hydrological processes over relatively complicated terrain, sea, and ice.

Adequate description of hydrologic processes is required in global models of the ocean-atmosphere-land system to improve the prediction of weather and climate at all time scales. Research is required to make best use of the data available from GCIP and other GEWEX large-scale observational programs to guide the formulation and validation of such hydrologic submodels. Improving the description of hydrologic processes in global models is a priority issue for GCIP which will be best addressed in collaboration with PILPS, ISLSCP, and the GEWEX Hydrometeorology Panel.

8.1.1 Research relating to the GEWEX Cloud Systems Study

The goal of the GEWEX Cloud Systems Study (GCSS) is to improve the parameterization of cloud systems in climate and NWP models. This objective will be achieved through a better quantitative knowledge of the physical processes involved in cloud systems as well as a quantification of their large-scale effects ( GCSS 1994). Key issues are described in Browning (1994). The investigation of continental cloud systems is part of the long-term objectives of the GCSS Working Group on Precipitating Convective Cloud Systems (Moncrieff et al. 1997).

One of the aims of GCIP is to improve the treatment of surface and hydrologic processes in NWP and climate models, but clouds have an important impact on these processes. GCSS involvement would contribute to the cloud component to GCIP, by way of cloud-resolving modeling and related activities. In turn, the GCIP data sets would be used to evaluate these models against observations.

Cloud Resolving Models

Cloud resolving models, identified by their ability to resolve cloud dynamics, are the approach of choice of the GCSS. These models derive from traditional nonhydrostatic cloud models but their scope is more ambitious. The effects of convection on the environment and the interaction among physical processes (boundary layer, surface layer, radiation, and microphysics) are the pacing issues, rather than individual processes per se. Since the time scales of some interactions (e.g., cloud--radiation) can be weeks, this is not only demanding on model design but also requires large computer resources.

When used to study precipitating convection (e.g. Grabowski et al. 1996a, b) or frontal cloud systems (Dudhia 1994) grid lengths of about 1km can be successfully employed to calculate bulk effects. Consequently, the domains of cloud resolving models span many NWP grid volumes. The time scales examined by 2D models is up to several weeks and these models are poised to address issues on intraseasonal time scales. An example is the effect of cloud-radiation interactions on the atmospheric and surface energy budgets (Wu et al. 1995b).

Cloud-resolving models also explicitly resolve convection-mean flow interactions that are impossible to accurately observe and since cloud-scale dynamics is explicitly simulated, one key uncertainty is minimized. Data sets from cloud resolving models can be used to evaluate single-column climate models - the testbeds for convective parameterization schemes. These data sets are also a key element in formulating new and more comprehensive approaches to parameterization.

Models need to be evaluated against atmospheric data sets. The GCIP region features several cloud system types, ranging from deep precipitating convection during the warm season, to frontal clouds dominated by ice processes in winter. GCIP will provide data sets for evaluating cloud resolving models, noting the relatively high density of routine observations over the U.S., not to say the special long-term observations available from the ARM/CART site.

Two different types of evaluation are required. First, an evaluation of the physical parameterizations used in cloud-resolving models (e.g., microphysics, turbulence, surface processes and radiation) is needed. However, this requires detailed cloud-scale observations, as well as intensive observation periods involving airborne platforms. Neither is available from GCIP.

Second, the effect of clouds on the environment directly relates to convective parameterizations in GCMs and is, in principle, an area to which GCIP can contribute. It is, however, far from a simple matter to utilize data collected during the GCIP Enhanced Seasonal Observing Periods (ESOPs) to evaluate the models.

A basic issue is: what is the minimum observational detail required to evaluate cloud resolving models? An ultimate answer will involve data assimilation in both regional and global models to "fill in" missing or data-void areas. However, present assimilation methods are neither a panacea nor even practicable on cloud resolving model grids. GCSS will therefore focus on basic problems such as the ensemble response of clouds (deep and shallow) to spatially-averaged, time-dependent forcing applied over scales comparable to or exceeding, climate model grid scales.


The GCSS has a cloud-resolving model intercomparison component. Modeling workshops have been conducted by the Working Group on Boundary Layer Clouds. Non-precipitating stratocumulus clouds in idealized environments were examined using Large Eddy Simulation models (Moeng et al. 1995).

The GCSS Working Group on Precipitating Convective Cloud Systems has an ongoing model intercomparison based on convection over the tropical western Pacific. The data set used in the model evaluation is from the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA COARE). To identify scientific and numerical issues as well as to minimize the complications and difficulties of modeling precipitating cloud systems, prototype numerical experiments were conducted (e.g. Grabowski et al. 1996a). This working group intends to move on to continental cloud systems in due course. The GCIP ESOP in 1996, that focused on the GCIP Large Scale Area-South West (LSA-SW) during the warm season, is an opportunity to study organized precipitating systems. A prototype experiment relating to GCIP could start as soon as adequate resources are available and the ESOP data have been analyzed.

GCSS/GCIP Projects

The following are candidate projects. Additional projects may arise; for example, noting that the 1997 GCIP ESOP will concentrate on wintertime processes, a GCSS initiative on frontal clouds is a possibility (Ron Stewart, private communication).

8.1.2 ISLSCP/GCIP Surface Flux Measurements

The purpose of the ISLSCP initiative within GCIP is to provide data sets that can be used to complement the operational and other research data sets being collected in the Mississippi basin. Particularly needed are sensible and latent heat fluxes and related measurements. The basic science question that the ISLSCP initiative will address is: Can the application of more complete bio-physical models and the development and application of relevant remote sensing algorithms be used to improve the quality of the continental-scale description of surface and water exchanges?

The strategy of the ISLSCP initiative will be to use flux towers to study temporal variability of fluxes at a point over an extended period of time and to use aircraft measurements to study spatial variability near the flux towers for selected times representing different seasons. This strategy will support investigations of scaling properties of land surface models and processes and the development and testing of approaches to estimate effective parameters for large areas.

The GCIP science plan (WMO 1992) identified one particular field campaign that cut across several GCIP scientific objectives. The year long field effort (with embedded IOPs) would be used to validate the largescale application of surface-atmosphere flux calculation models forced by remote sensing data, standard meteorological observations, and analyses thereof. This project would provide the following missing components, which are directly relevant to the large-scale objectives of GCIP:

The provision of these additional quantities would not only close the water and energy budget equations for the region but would also provide more detailed information on the spatial distributions of moisture and energy sinks and sources within the experimental area. Measurement and modeling techniques developed with ISLSCP over the last five years could be used to address these missing components.

NOAA has already started a contribution to this effort with a new flux tower operating since May, 1995 in the Little Washita area of Oklahoma. Also augmentation of a flux tower at Oak Ridge, Tennessee has occurred and a third flux tower was added in 1996 at Bondville, Illinois.

In keeping with the philosophy of an effective, directed but economic field effort the following measurements are proposed.

8.2 Collaboration with the Atmospheric Radiation Measurement Program

Since 1993, GCIP has been coordinating many of its data collection activities with the Atmospheric Radiation Measurement (ARM) to achieve synergistic benefits from the outstanding observation facilities established by ARM at the southern great plains Clouds and Radiation Testbed (CART) in Oklahoma and Kansas. In this regard, the soil water and temperature system (SWATS) is a joint venture between the GCIP and ARM. The GCIP has provided the SWATS and data loggers, and supported their installation. The ARM Program is supporting the operation of the system.

Given the fact that the ARM program is investigating radiative transfer processes in the atmosphere as its highest priority at a site within the GCIP study area, GCIP will continue to collaborate with ARM via the existing ARM/GCIP/ISLSCP working group. However, there is a need for GCIP to take a more active role in developing a new joint focus of interest between ARM and GCIP in the area of measuring and modeling the warm season convective production of clouds and precipitation. This is an emerging joint interest of high priority to both scientific programs that should be addressed as a collaborative initiative over the next few years.

8.3 Collaboration with NASA Initiatives in the Mississippi River Basin

Several aspects of the NASA program relate direct to priority science of GCIP. The field studies on soil moisture in the ARM/CART region in 1997 relate directly to some of the science discussed in Section 6, and active collaboration should be sought between GCIP coupled modeling scientists and NASA observational scientists to secure maximum scientific benefit from that study. Equally, NASA and NOAA share an interest in providing improved management of water resources in the GCIP LSA-E, most probably through the Tennessee Valley Authority. Both agencies also share an important common interest in documenting, understanding and, to the extent possible, predicting seasonal-to-interannual variability in the southwest monsoon season, and evaluating the consequences of that variability on the vulnerable human management systems in that region.

8.4 Collaboration with PACS and GOALS

Prediction of weather and climate is made with models which include description of the entire global domain and which, in consequence of technical constraints, necessarily operate with a level of spatial and temporal precision that is inconsistent with the hydrological interpretation of their predictions over continents. Increased specificity in space and time is possible using regional models which operate over a more limited continental domain. In order to allow hydrological interpretation of weather predictions at seasonal-to-interannual time scales, research is required to foster and demonstrate effective coupling between regional models of atmospheric and hydrologic systems on the one hand and global models of atmospheric and oceanic systems on the other.

GCIP is working with the Pan-American Climate Studies (PACS) portion of the GOALS Program to develop a plan for joint studies centered on the North American monsoon system. Such research will include interfacing regional coupled atmosphere-land system models with global coupled ocean-atmosphere models as an important scientific focus.

8.5 Collaboration with the US Weather Research Program

The US Weather Research Program (USWRP), which is jointly funded by NOAA and NSF, has as one of its major goals the development of techniques to improve quantitative precipitation forecasts over short time scales. As part of this process the USWRP has been holding small workshops on relevant issues including precipitation prediction. GCIP is exploring areas of common interest to the USWRP with a view to initiating some joint studies in precipitation estimation and prediction. The data collection for ESOP-95 was carried out as a joint undertaking with the USWRP WAVE project.

8.6 FAA Collaboration - The Water Vapor Sensing System (WVSS) for Commercial Aircraft

Water vapor is ubiquitous, energetically important and volatile, highly variable in space and time, and unfortunately, poorly measured by current methods. The water vapor information from the twice-per-day radiosonde sites will be marginal for the diagnostic budget studies to be performed for GCIP. Two major systems can be used during GCIP to augment these radiosondes. The first of these is to add ascent and descent profiles from commercial aircraft. The second approach is to make greater use of the water vapor channel information from geostationary satellites. Here, however, one needs to continuously calibrate the satellite information because of its vertical-error structure. The horizontal gradient structure in water vapor as seen by the satellite is quite good; however, the data from the commercial aircraft is needed to calibrate the satellite data and provide both the vertical consistency and the missing lower tropospheric water vapor information that the satellite cannot see.

The commercial aircraft high resolution sounding will provide winds, temperature, and water vapor (discussed below). Such profiles will aid the research goals stated in Section 5 concerning the ability to improve water balance calculations with soundings at a far greater frequency than twice per day. Such water vapor profiles will also contribute to the precipitation research discussed in Section 6.

The development of a water vapor sensing system (WVSS) for commercial air carriers was funded by the FAA under the Commercial Aviation Sensing Humidity (CASH) Program. NOAA's Office of Global Programs (GCIP) is now co-funding the procurement phase with the FAA (which is now called the WVSS program). A competitive contract was awarded to Lockheed Martin Corporation (LMC) in July 1995.

1998 Activities

Data from the first commercial aircraft with the WVSS was continuously available for the last four months of WY97. We are achieving an excellent dynamic range of mixing ratio information, the data comparison between ascent and descent from the same air terminal has been consistent, and comparisons against radiosondes (when possible) have been quite good with consistent vertical changes in degrees of wetness. All of our error quality control checks also appear to be working as we gave them to Allied Signal.

This first aircraft was a United Parcel Service (UPS) B-757. FAA certification for all B-757 was finally granted in August 1997. Installation for the next five WVSS units on UPS aircraft began in September 1997 and is expected to be completed in November 1997. The government exercised an option in the LMC contract for 60 additional units in September 1997.

A radiosonde intercomparison test of the six WVSS units and radiosondes launched at Louisville, KY (there is currently no radiosonde site at the UPS hub), will occur in November 1997. This is being co-funded by this project and the National Weather Service. The UPS labor strike, other FAA delays, and the reduced GCIP budget for this program have all contributed to a delay in the government's decision on the next 60 units. Subsequently, the production team for the WVSS must be reassembled and the delivery of the next 60 units can only begin in February 1998 and be completed by the end of fiscal year 1998. However, considerable work can be accomplished with the first six WVSS units (they provide 24 ascents and 24 descents per day) toward data evaluation and new 4DDA algorithms for water vapor information being combined with satellite data. By the end of the year the 66 WVSS units will be providing 264 new water vapor profiles each day, primarily over the GCIP region. The descent and en route data will also contribute to the satellite calibration and water vapor flux calculations.

Evaluation of the data will be performed by NOAA Forecast Systems Laboratory (FSL) for GCIP and the FAA. Quality-controlled data sets of wind, temperature, and water vapor from the commercial aircraft will be made available through the GCIP in situ data source module described in Section 9.

1999 and 2000 Activities

A second contract option for an additional 100 WVSS units will be made in FY98 as originally planned; however, due to GCIP budget decreases for this program, the full amount of money for this option is not available. The current price for this option is approximately $9K per unit and $6K for installation. The FAA has agreed to continue their share in FY99 and thus pay

back a lender of funds in FY98. If GCIP continues to fund this program at the current rate (including a similar FY99 commitment), then approximately 80 of the 100 units can be procured. This would provide the last two years of GCIP with water vapor information from 146 aircraft. Moreover, the WVSS can be continued into the future for a continued GCIP/PACS project as once the capital costs for the WVSS have been paid, the operational and maintenance cost are trivial.

8.7 Cooperative Atmospheric-Surface Exchange Study (CASES)

CASES is a facility of about 5000 km2 to study mesoscale processes of and linkages among meteorology, hydrology, climate, ecology and chemistry, in the upper Walnut River watershed, north of Winfield, Kansas. This is located within the ARM/CART site. Boundary layer instrumentation, in conjunction with WSR-88D radars, stream gauges, soil moisture data, topographical and land use data, mesonet surface data, and coupled atmospheric-hydrologic models, will produce data sets useful to GCIP SSA and ISA studies when this facility is fully implemented.

CASES will provide seasonal and interannual information on precipitation, soil moisture, runoff, vegetation, evapotranspiration, and atmospheric thermodynamics, which will allow modelers to not only define the surface hydrology but approach closure on the hydrologic cycle between the atmosphere and the watershed as well. CASES will provide a comprehensive data set on a scale which will allow aggregate testing of model structure and model parameters derived from studies of the Little Washita watershed and the FIFE experiment.

Initial activities are ongoing to prepare a retrospective data set for the Walnut River basin. Further plans exist for implementing some of the sensor systems identified above, and these will be implemented as resources become available.