This section describes the progress and near-term plans for observation enhancements largely supported by GCIP. It also summarizes the plans for data products with emphasis on the critical variables described earlier in section 6.

10.1 Precipitation Measurements and Analysis

It is a goal of GCIP to contribute to the development of a derived product which combines WSR-88D, gauge, and satellite estimates of precipitation resulting in a product with a 4-km spatial and hourly temporal resolution. Such a goal is not expected to be achieved for a routine product until much later in the EOP since it is dependent upon some of the modernization improvements yet to be implemented by the NWS.

OBJECTIVE: Produce the best possible estimates of spatial and temporal distribution of precipitation at time increments of one hour to one month and spatial increments of 4 to 50 km.

GCIP requires the best available precipitation products and recognizes the potential value of the WSR-88D radars in meeting this requirement. Combined radar and gauge-based precipitation fields are expected to provide better estimates of precipitation than estimates based on raingauge values only. However, the limitations of radar estimates need to be evaluated because these are not well enough understood to provide research quality data sets over continental-scale areas.

Associated with the measurement of precipitation caught by the gauge is the question of representative exposure of the gauge and the effect of not having wind shields or the characteristics of different shields on gauge catch, evaporation, etc. The systematic correction of gauge errors is a necessary requirement for the development of good-quality precipitation fields. The National Climate Data Center (NCDC) applies basic quality control techniques to the cooperative observer network, but quality control and gauge error correction of all the operational data that might be used in a national precipitation product are major tasks that could require the development of new techniques.

Two task summaries are given for precipitation:




TASK TITLE -- 10.1.1 Precipitation Analysis

OBJECTIVE -- To provide the precipitation analysis products from the NCEP operational analysis to the GCIP Data Management System

PRODUCT DESCRIPTION -- The current product consists of a national daily precipitation analysis at a 40 km resolution based on the gauge only measurements collected in near real time at the NCEP. This is an operational product produced by the NCEP beginning in the summer of 1994.

PROJECTED IMPROVEMENTS -- Evolutionary changes will occur as part of a Stage IV national precipitation composite mosaic being implemented at the NCEP. An interim real-time Stage IV national product will be produced hourly beginning in the summer of 1996, using real-time Stage I products and gauge data as well as any Stage III products then available. Improvements in the spatial and temporal resolution will also be made during this period.

GCIP DATA SOURCE MODULE-- Model Output (Contact: R. Jenne, NCAR)

SCHEDULE- Operational product sent by NOAA/NCEP each month to the GCIP Data Source Module.

GCIP USER AVAILABILITY - Three months after the end of the analysis month.

RESOURCE SUPPORT- Development support from NOAA GCIP Program through the NWS CORE Project for GCIP. The operational product is a contribution from the NOAA/NCEP






TITLE -- 10.1.2 Precipitation Observation Composite

OBJECTIVE -- To provide a quality controlled composite of all available precipitation observations in a common format.

PRODUCT DESCRIPTION -- The precipitation composite contains precipitation data from all real- time and recording gauges in the geographic domain as both hourly and daily totals. The Composite is produced by the In-Situ Data Source Module using data from up to 14 different observing networks. A precipitation observation composite was produced for each of the GCIP Initial Data Sets.

PROJECTED IMPROVEMENTS -- Evolutionary improvements in quality control procedures will be implemented as proven techniques warrant. There are no current plans to correct for measurement errors by the different sensor systems.

GCIP DATA SOURCE MODULE -- In-Situ (Contact: S. Williams)

SCHEDULE -- Continuing as the observation data become available. Data from the NWS Cooperative Network is the last available and determines the completion schedule for a particular month. A Composite for a specific month is expected to be completed about six months later with a nominal collection schedule by all the networks.

GCIP USER AVAILABILITY -- The In-Situ Data Source Module will make the data available on-line through the World Wide Web as composites are completed for monthly periods. The Composite for a complete EOP year is projected to be available about nine months after the completion of the EOP year. The data for the first year of the EOP will be available about June 1997.




10.2 Snow and Snow Water Equivilant

OBJECTIVE: Develop improved parameterizations of snow processes, develop supporting data sets, and develop improved spatial estimation techniques for orographic precipitation and snow.

Point snow measurement relies primarily on the Soil Conservation Service (Natural Resources Conservation Survey) SNOpack TELemetry (SNOTEL) network, which is largely to the west of the Mississippi River basin, and a comparatively sparse network of snow depth measurements at NWS synoptic stations. Snow courses are measured by various agencies, but these are limited and are restricted to the higher snowfall areas. Remote sensing offers a more practical approach to assess snow over large areas and this is addressed in the next section. However, the need for new techniques or additional ground truth measurements has to be considered.

The program in NESDIS is focused on the development of an interactive system for producing daily, rather than the current weekly, Northern Hemisphere snow maps on Hewlett Packard 755 UNIX-based workstations from a variety of satellite imagery and derived mapped products in one hour or less. Resolution of the final product will be improved from 190 kilometers to 23 kilometers. Ultimately, the final product will also provide information on snow depth in addition to snow cover.

10.3 Cloud Data Products

Several satellite-based cloud data sets will be generated during the course of the EOP, based on both POES and GOES observations: ASOS (GOES), CLAVR (POES), and high-resolution (time and space) clouds (GOES).

A gridded version of the Automated Surface Observing System (ASOS) clouds will be generated for GCIP as a continental-scale product. The ASOS clouds are produced operationally from GOES at weather station locations to supplement the laser ceilometer observations of the ASOS of the modernized weather service. The ASOS clouds are generated from the GOES sounder using the carbon dioxide slicing technique (Menzel and Strabala, 1989; Wylie and Menzel, 1989). They can also be generated from the image data by substituting the water vapor channel for the carbon dioxide band. Whether the sounder or imager version is implemented depends on which technique is chosen by the NWS for the operational ASOS product. In addition to cloud information, the ASOS-cloud processing system produces clear sky surface temperature as an intermediate product, which will be evaluated for surface energy budget studies and validation of the Eta and other models.

CLAVR stands for clouds from the advanced very high resolution radiometer (AVHRR) on the POES. NESDIS has developed this cloud product over the last few years, and it is currently being generated on a routine basis from the afternoon POES observations (Stowe et al., 1991). This product includes cloud amount, type, and height of each cloud type at a resolution of one degree in latitude. During GCIP it will be produced routinely on a global basis by NESDIS for day and night from both POES spacecraft. The NESDIS will access the product to produce a CONUS sector for the GCIP database.

The ASOS cloud product produced from the GOES data meets the needs of GCIP users better than the CLAVR cloud product produced from POES data. We shall therefore select the ASOS product as the best available now" for GCIP with the CLAVR to be used in the event of difficulties with the ASOS product. A summary of the clouds task is given in Task 10.3.1.




TASK TITLE -- 10.3.1 Cloud Products

OBJECTIVE -- To provide the cloud products from the operational NESDIS output to the GCIP Data Management System

PRODUCT DESCRIPTION -- The ASOS cloud product is produced from GOES image and vertical sounder data each hour for the geographical domain of the continental U.S (CONUS).

PROJECTED IMPROVEMENTS -- This is a relatively new satellite derived product so that any improvements need to await reactions from the users.

GCIP DATA SOURCE MODULE -- Satellite Remote Sensing (Contact: B. Motta)

SCHEDULE -- Data are archived on a routine basis

GCIP USER AVAILABILITY -- Within three months after the observation time

RESOURCE SUPPORT -- Development support from the NOAA GEWEX Program through the NESDIS portion of the CORE Project for GCIP. The operational product is a contribution from the NOAA/NESDIS.

TASK LEADER -- D. Tarpley

GCIP PRA COORDINATION -- Clouds and Radiation

10.4 Radiation Data Products

Radiation data sets are required for the GCIP EOP on a continental scale. This information will include top-of-the-atmosphere, surface, and atmospheric radiation data based on both POES and GOES observations.

10.4.1 Outgoing Longwave Radiation (OLR) and Planetary Albedo

The OLR and planetary albedo radiation budget products have been obtained from multispectral, narrowband radiometric scanners for many years. This product is currently being produced using a technique to infer the OLR from four of the channels on the high-resolution infrared sounder (HIRS) flown on the POES(Ellingson et al., 1989; Ellingson et al., 1994a).

The above methodologies for obtaining top-of-the-atmosphere, OLR, and planetary albedo are being applied to GOES-8 data and are being produced for GCIP.

10.4.2 Surface and Atmospheric Radiation Budget Components

In addition to the OLR, methods have been developed to infer the downward longwave radiation (DLR) flux at the surface (Lee and Ellingson, 1990) and the vertical profile of longwave cooling (LC) (Shaffer and Ellingson, 1990; Ellingson et al., 1994b) from POES observations. The DLR and LC estimation techniques require spectral radiance data from the HIRS and the vertical distribution of cloud amount and cloud base height. The NESDIS is implementing the techniques in an experimental operations test in the TOVS sounding system.

Insolation and photosynthetically active radiation (PAR) for the GCIP CSA (and in fact, for the whole U.S.) will be produced from GOES 8/9 imager observations. The insolation algorithm, developed at the University of Maryland (Pinker and Ewing, 1985; Pinker and Laszlo, 1992) is a physical algorithm that uses GOES imager observations of reflected visible radiation. The algorithm uses target clear radiance, target cloudy radiance, fraction of clouds in the target and atmospheric precipitable water (from the Eta model). Other required input to the model is surface albedo (Matthews, 1985) and snowcover. Net solar irradiance at the surface can be derived from the insolation and surface albedo.

This algorithm has been modified at the University of Maryland to use GOES 8/9 data as input. A two threshold cloud detection method has been developed that provides the clear and cloudy radiances and the fractional cloud cover required by the algorithm. Over the past two years the insolation algorithm has been implemented into the GOES sounding system at NESDIS and routine production has begun. The products are not operational, however, but are currently experimental and generated specifically for GCIP.

Because the insolation algorithm is newly developed for GOES 8/9 data, it is vital that the insolation estimates be compared with ground truth and all aspects of the procedure, from cloud detection through insolation production, and be subject to modification and improvement. This way, the accuracy and reliability of the products will increase, thereby meeting one of the main objectives of GCIP.

Outgoing longwave radiation, DLR at the surface, and atmospheric LC rates will be derived from GOES-8 by applying the methodologies used to generate these quantities from POES-HIRS observations. Some development is needed to apply the techniques to GOES data.

In the case of clear skies, surface temperature measurements will be obtained as a byproduct of the ASOS clouds processing. These measurements can be used to obtain upward longwave radiation fields at the surface, which can be combined with the DLR to obtain net longwave irradiance at the surface for clear skies. A summary of satellite radiation budget data setsto be generated for the EOP is contained in Table 10-1.

Table 10-1 Satellite Radiation Budget Data Sets for GCIP Continental-Scale Area during the EOP

PRODUCT INSTRUMENT RESOLUTION FREQUENCY -------------------------------------------------------------------- POES Outgoing LW AVHRR 0.7 Deg 4/day Planetary Albedo AVHRR 0.7 Deg 4/day Downward LW HRS 1.0 Deg 4/day LW Cooling Rate HRS 1.0 Deg 4/day Outgoing LW HRS 1.0 Deg 4/day GOES Outgoing LW Sounder 0.5 Deg hourly Downward LW Sounder 0.5 Deg hourly LW Cooling Rate Sounder 0.5 Deg hourly Insolation/PAR Imager 0.5 Deg hourly

There is another source of surface temperature that should be considered for GCIP. This is the Derived Product Imagery (DPI) which includes surface skin temperature, lifted index, and total precipitable water. The DPI is a planned operational suite of products from the GOES 8/9 imager that is currently under active development. The resolution of the surface temperature in the DPI is 4 km, so in addition to averages of surface temperature for targets of about 50 km. resolution, histograms of surface temperature could be saved. This could be of considerable interest to the modeling community.




TASK TITLE -- 10.4.1 Satellite Radiation Data Products

OBJECTIVE -- To provide the satellite radiation products from the NESDIS to the GCIP Data Management System

PRODUCT DESCRIPTION --Radiation products produced from the POES and GOES satellites

PROJECTED IMPROVEMENTS -- Outgoing longwave radiation , downward longwave radiation at the surface and atmospheric longwave cooling rates from GOES 8 type data is now being developed and will be added by the end of the first year of the EOP. Some limited data sets are projected to be available during the ESOP-96 in the LSA-SW

GCIP DATA SOURCE MODULE -- Satellite Remote Sensing (Contact: B. Motta)

SCHEDULE -- Data are archived on a routine basis

GCIP USER AVAILABILITY -- Within three months after the observation time

RESOURCE SUPPORT -- Development support from the NOAA GEWEX Program through the NESDIS portion of the CORE Project for GCIP. The operational product is a contribution from the NOAA/NESDIS.

TASK LEADER -- D. Tarpley

GCIP PRA COORDINATION -- Clouds and Radiation

10.4.3 SURFRAD Sites for GCIP

Six Surface Radiation (SURFRAD) sites are planned for the contiguous 48 states (three of these are already installed in the Mississippi River basin). This network is intended to provide high quality, long-term solar and infrared radiation measurements for a variety of research needs: to validate satellite-derived surface insolation; to provide a long-term climatology of surface radiation measurements (at least 25 years); to detect trends in surface radiation; and, to verify radiative transfer models. The basic instrumentation set (see
Table 10-2) includes radiometers for upwelling and downwelling solar and INFRARED radiation, a sun-tracking normal incident pyrheliometer (NIP) for measuring direct solar irradiance, and a meteorological tower. Other special sensors may be added.

Table 10-2 Basic Instrumentation at a Surfrad Site.
Measurment                        Name                             Cost ($)        Accuracy
Direct Solar Irradiance   Cavity radiometer (required at BSRN)      18,000         2 W/m^2
                          shadow band radiometer NIP                10,000
                                                                     1,800         5 W/m^2
Diffuse Solar             Pyranometer (2pi solar flux)               1,800         5 W/m^2
                          (radiation >2.5 pm filtered out)
Global Solar              Pyranometer                                1,800        10 W/m^2
  (direct and diffuse)    (no tracker)
Reflected Shortwave       Inverted pyranometer                       2,000        10 W/m^2
                          (shaded from sun)               
Downward Longwave         Pyrgeometer (filtered pyranometer)         2,850       6-8 W/m^2
Upward Longwave           Inverted Pyrgeometer                       2,850       6-8 W/m^2
Photosynthetically        PAR Instrument                              200         TBD
  Active Radiation        (filtered silicon detector)  
Surface Meteorology Tower 10-m height:  winds, pressure,             6,000        TBD
                          temperature, humidity

The URL http://www.srrb.noaa.gov has detailed information on SURFRAD sites, instrumentation, and access to data. In addition to the instrumentation mentioned on Table 10-2, NOAA has obtained Multi-Filter Rotating Shawdowband Radiometers (MFRSR) for SURFRAD. Operation MFRSR algorithmss retrieve column aerosol optical depth, predictable water, and ozone; research algorithms provide cloud optical depth. The SURFRAD combination of broadband and MFRSR measurments will permit the estimation of aerosol direct radiative forcing to climate over GCIP.

SURFRAD sites have been chosen to be representative of extended regions. Each has reasonably uniform and stable surface properties that are representative of the region. This requirement is the primary concern of those doing verification of satellite-based algorithms. Those who will use SURFRAD data to verify the satellite-derived surface radiation data require that the area surrounding the sites be spatially uniform over at least the area of one GOES-8 sounder pixel, which is 10 km (E-W) by 40 km (N-S).

One SURFRAD site in the GCIP region is at Bondville, Illinois, located approximately eight miles southwest of Champaign, Illinois. It is owned by the University of Illinois Electrical Engineering Department and managed by the Illinois State Water Survey. This site consists of six acres of grassland (being updated to 14 acres) and surrounded by 220 acres of soybeans and corn. This site is currently operational and also contains a suite of aerosol measurement systems operating under a separate NOAA funded aerosol monitoring program. A second SURFRAD site in the GCIP region is the Poplar River site (near Fort Peck, Montana). The Poplar River flows south out of Canada and into the Missouri River. This site has good hydrological data available and the Poplar River is not used for irrigation (because of high levels of alkali). The site is on rangeland with no trees in northeastern Montana. This site was operational in the summer of 1994. A third SURFRAD site in the GCIP region is the Goodwin Creek site (near Oxford Mississippi). The Goodwin Creek Experimental Watershed is an ARS site located in northern Mississippi. It is relatively flat, and its land use is about 14 percent agricultural, 26 percent timber, and 60 percent idle pasture land. Four lakes are in the region. This site was operational in the fall of 1994.

1997-1998 Activities

In addition to the usual radiation and hydrological measurements at the three SURFRAD sites identified earlier, funds have been requested to add instrumentation for the following: soil moisture, snowfall measurements (in the northern sites), ground heat flux, and cloud determination via lidar and/or possibly digitized pictures.

The data from these sites will be quality controlled by NOAA's Air Resource Laboratory (ARL) in Boulder, Colorado. Data will be archived at the ARL facility in Oak Ridge, Tennessee and accessible via the GCIP in situ data source module.

1998 Activities

Not all the requested instrumentation will be immediately available at all the GCIP SURFRAD sites. It is expected that further implementation of instrumentation will likely occur as more resources become available and become part of the normal operations at the three SURFRAD sites.

10.5 Soil Moisture Profiles

The few routine soil moisture observations available for GCIP applications is being significantly enhanced during the next two to three years; primarily as a result of sensors installed in the Little Washita Experimental Watershed and the ARM/CART site combined with planned enhancements to the Oklahoma Mesonet. The situation in the LSA-SW is such that GCIP can potentially compile in-situ soil moisture measurements on three different scales using automated soil moisture sensing systems:

Six soil moisture sensing systems were installed in the Little Washita Watershed in the summer of 1995. An additional seven sensor systems were installed in this Watershed during 1996.

A total of 22 soil moisture sensing systems are being installed within the ARM/CART site. The first seven were installed and operating by the beginning of ESOP-96 in April 1996 and an additional 12 installed by the end of Water Year 1996. An example of the relative soil moisture response curves in the ARM/CART site is given in Figure 10-1 which was very dry during the spring and early summer. The Campbell Scientific Heat Dissipation Soil Moisture Sensor (Model 229L) provides data from six different depths as shown in Figure 10- 1. The calibration to convert the sensor is not yet completed. Therefore, the relative response in degrees celsius is given in the figure with lower values wetter and higher values drier. The curves from Ashton in May 1996 are typical of the response from many sites this spring and summer. The soil was very dry throughout the profile, and what little rain fell did not infiltrate very deeply into the profile. At Ashton, the rain on May 10th wetted the top two sensors, with only a slight amount of moisture penetrating as far as the 35-cm sensor.


Figure 10-1 Relative soil moisture response curves for Ashton, OK during May 1996 from the Campbell Scientific Heat Dissipation Soil Moisture Sensor.

The Oklahoma Mesonet is planning to install soil moisture sensing systems at about half of their 109 stations in the state-wide mesonetwork.

An initial soil moisture data set for both the Little Washita and the ARM/CART site will be compiled during as part of the ESOP-96 data set. It is projected that in-situ soil moisture measurements on the three different scales noted above will become available in a more complete sense during the second year of the EOP in WY97.

Also during WY97 a soil moisture analysis for at least a portion of the LSA-NC can be made by making use of soil moisture measurements from the Illinois State network plus other sites available in the LSA-NC. Task 10.5.1 outlines the task for providing soil moisture analysis from observations. Task 10.5.2 outlines a task for deriving soil moisture from a hydrologic model for evaluation by the in-situ measurements.




TASK TITLE -- 10.5.1 Soil Moisture Analysis from Observations

OBJECTIVE -- To develop an analyzed soil moisture product for portions of the Mississippi River basin in evolutionary steps over the next two to three years.

PRODUCT DESCRIPTION -- A series of analyzed products will be produced for different temporal and spatial scales based on both the GCIP needs and the availability of suitable data for such analyses.

PROJECTED IMPROVEMENTS --The soil moisture analysis will start out with relatively simple procedures over those areas having suitable data. The analysis techniques will become more sophisticated over time. Also, the ability to incorporate remotely sensed data will enable the analysis product to be extended geographically beyond those areas having in-situ measurements.

GCIP DATA SOURCE MODULE -- In-Situ (Contact: S. Williams)

SCHEDULE --to be determined

GCIP USER AVAILABILITY --to be determined

RESOURCE SUPPORT -- In-Situ measurements being supported by several sources. Development of analyzed product support is to be determined.

TASK LEADER -- to be determined





TASK TITLE -- 10.5.2 Soil Moisture from Hydrologic Model

OBJECTIVE -- To validate a capability of providing soil moisture data from hydrologic model(s)

PRODUCT DESCRIPTION -- It is anticipated that soil moisture analyses can be derived as part of a model output from a model such as the Land Data Assimilation System. Thus, it can be argued that these models will provide a more realistic simulation of the soil moisture changes, both in time and space.

PROJECTED IMPROVEMENTS -- To be determined after demonstration of initial results from model.

GCIP DATA SOURCE MODULE -- to be determined



RESOURCE SUPPORT -- Several different models are in different states of development and supported by NOAA/GCIP and other agencies. The development of the LDAS is supported by the NOAA/GCIP Program through the NWS portion of the CORE Project for GCIP.

TASK LEADER -- E. Engman for Soil Moisture PRA, J. Schaake and K. Mitchell for the NOAA/NWS CORE Project for GCIP.

GCIP PRA COORDINATION -- Jointly between the Coupled Modeling and Data Assimilation

1998 Activities

Temperature and volumetric water content will be made to a depth of 1.3-2.0 meters (site dependent). Eight to ten measurements will be made over that depth. Analysis of this data will be an on-going project.

10.6 Soil Temperature Profiles

Soil temperature profiles or subsurface heat flux profiles are being measured in the ARM/CART, Little Washita micronetwork, and Oklahoma mesonetwork at the locations providing the soil moisture profile measurements.

10.7 Land Surface Data Products

The derived data products for land surface characteristics are described within the categories of vegetation/land cover, soils and topographic data products.

10.7.1 Vegetation and Land Cover Data Products

Some of the sources for vegetation/land cover characteristics data include the global one-degree latitude-longitude modeling data sets recently published on CD-ROM by NASA/GSFC under GEWEX/ISLSCP Initiative No. 1 and various AVHRR data sets produced by NOAA/NESDIS and USGS. For example, NASA's ISLSCP CD-ROM includes monthly one-degree by one-degree calibrated, continental NDVI data (1982 to 1990); enhanced NDVI fields; Fraction of Absorbed Photosynthetically Active Radiation (FPAR) fields derived from enhanced-NDVI data; LAI and canopy greenness resistance fraction calculated from the derived FPAR fields; surface albedo and roughness length fields derived from land process models; and canopy photosynthesis and canopy conductance fields estimated by inverting the Simple Biosphere (SiB) Model 2 land surface parameterization (LSP) with FPAR as the key model input. The CD-ROM also includes a one-degree global land cover data set developed under the leadership of the University of Maryland.

Although these ISLSCP Initiative No. 1 CD-ROM data are of direct interest to GCM and possibly mesoscale modeling, the remote sensing algorithms and approaches for inverting an LSP to derive the land cover characteristics will guide efforts to similar use of higher resolution AVHRR and LANDSAT TM data. NASA/GSFC is currently implementing ISLSCP Initiative No. 2 which focuses on enhanced global land cover characteristics data sets at a 1/2-degree latitude-longitude grid.

The NOAA/NESDIS has developed AVHRR global vegetation index (GVI) data sets. These data sets include weekly satellite image composites consisting of five AVHRR channels, solar zenith and azimuth angles, and the GVI for 1985 to the present. These data are calibrated for sensor drift and intersensor variability, and are available in a 1/6-degree resolution latitude-longitude product. Recently, NOAA/NESDIS produced a five-year climatology of the GVI data, and is now working to derive vegetation fraction from the GVI. The NOAA/NESDIS is also working with NASA/GSFC on the AVHRR Global Area Coverage (GAC) Pathfinder project to develop calibrated 8-km AVHRR data with a period of record beginning in 1981.

The USGS EROS Data Center (EDC) has developed 1-km AVHRR databases for the conterminous United States and is now processing global 1-km AVHRR data for land areas. The databases for the conterminous United States include biweekly AVHRR time-series image composites on CD-ROM (1990-1994) and a prototype land cover characteristics database for 1990 on CD-ROM. This 1990 land cover characteristics database is currently undergoing validation based on field survey data. Ongoing USGS activities also include the preliminary development of experimental, temporally smoothed 1-km seasonal NDVI greenness statistics for test and evaluation. These statistics consist of 12 seasonal characteristics that are associated with each 1-km NDVI seasonal profile for each year during the period 1989 to 1993, as well as the five-year means throughout the conterminous United States. Under the auspices of the International Geosphere Biosphere Project (IGBP)-led 1-km AVHRR global landcover database development activity, the USGS is currently processing global, 10-day AVHRR image composites for land areas. Efforts to develop a 1-km AVHRR North American land cover characteristics database are well under way, with some testing underway in 1995. Several global climate change research modelers are currently testing and evaluating these USGS data sets.

10.7.2 Soils Data Products

The STATSGO database provides the most useful resource for characterizing the role of soil in mesoscale atmospheric and hydrological models. This database was developed by generalizing soil-survey maps, including published and unpublished detailed soil surveys, county general soil maps, state general soil maps, state major land resource area maps, and, where no soil survey information was available, LANDSAT imagery. Map-unit composition is determined by transects or sampling areas on the detailed soil surveys that are then used to develop a statistical basis for map-unit characterization. The STATSGO map units developed in this manner are a combination of associated phases of soil series.

The STATSGO database will be useful for regional-scale analysis; however, GCIP researchers will require, on a selective basis, SSURGO data for detailed watershed studies and intense field observation programs. Although this database will not be complete for the entire United States or even the GCIP study area for many years, selected watersheds within the Mississippi basin should have this, or similar coverage, within the EOP. The SSURGO and STATSGO databases are linked through their mutual connection to the NCSS Soil Interpretation Record (Soil-5) and Map Unit Use File (Soil-6).

Doug Miller at Penn State University is developing a multi-layer soil characteristics dataset based on the STATSGO for application to a wide range of SVAT, climate, hydrology and other environmental models. A more detailed description of this dataset is given on the World Wide Web at the URL address: http:\\eoswww.essc.psu.edu\soils.html

10.7.3 Topographic Data Products

Topographic information includes surface elevation data and various derived characteristics such as aspect, slope, stream networks, and drainage basin boundaries. In general, the requirements of atmospheric modelers for topographic data (i.e., spatial and vertical resolution and accuracies) are much less demanding than the requirements for hydrological modeling. For example, available DEMs for the conterminous United States (0.5 km and approximately 100-m resolution) are generally adequate for most atmospheric modeling. A 60-m DEM derived by USGS from 2-arc second elevation contours is available for the entire ARM/CART region and other selected quads.

The 100-m DEM is generally appropriate for hydrological modeling in large basins (e.g., greater than 1,000 km2 in area). However, topographic data for small basins down to watersheds are needed at two general hydrological scales: hillslope and stream network. The hillslope scale is the scale at which water moves laterally to the stream network. Available USGS 60 m DEMs derived from 2-arcsecond contour data are generally available for the ARM/CART region.

Hillslope flow distances vary and may be as great as 500 m to 1 km. Definition of hillslope flow paths and the statistics of hillslope characteristics require surface elevation data at about 30 m spatial resolution. Such data have been digitized by the USGS from 1:24,000 scale map sheets for part, but not all of the Mississippi River basin. Also, stream locations (but not drainage boundaries) are available in vector form for these map sheets. Because 30- m resolution data are not available globally nor in some parts of the Mississippi basin, research is needed to see how well hillslope statistics, that are important to some hydrological models, can be estimated from topographic properties of lower resolution terrain data. Research is also needed to determine how important hillslope information is to hydrological response of the land surface. Because 1:24,000 scale maps are not available globally, research is needed on how best to use remote sensing techniques as part of a sampling strategy to develop regionalized hillslope statistics (which may be mapped at an appropriately large scale).

10.8 Surface and Ground Water Measurements

The primary observations of hydrological variables are from in situ networks and consist of stream gauges, measuring wells, measurements of water storage in large reservoirs, soil moisture, evaporation and estimates of snow cover. GCIP is treating soil moisture as a separate variable (see Section 10.5) and also estimates of snow cover. (see Section 10.2). There are few measurements of evaporation available. This leaves stream gauges, measuring wells and measurements of water storage which are needed to provide derived information for computing water budgets. In cooperation with many other Federal, state, and local agencies, the USGS collects water data at thousands of locations throughout the nation and prepares records of stream discharge (flow), and storage in reservoirs and lakes, ground-water levels, well and spring discharge and the quality of surface and ground water. The number of stations collecting such data was summarized in Table 1 of the GCIP Implementation Plan, Volume I (IGPO, 1993), and is updated for each of the data sets compiled by GCIP.

Most of the gauged streams in the Mississippi River basin are affected by various water management activities such as upstream storage and diversion for human activities and irrigation. The USGS has a hydrological benchmark network of 58 stations virtually unaffected by human activity distributed across the United States (Lawrence, 1987). Wallis et al. (1991) prepared a set of 1009 USGS streamflow stations for which long-term (1948-88) observations have been assembled into a consistent daily database and missing observations estimated using a simple closest station" prorating rule. Estimated values for missing data, as well as suspicious observations, are flagged. The data are retrievable by station list, state, latitude-longitude range, and hydrologic unit code from a CD-ROM. This data set is being updated to include the years since 1988 with primary emphasis on those stations important to GCIP. Landwehr and Slack (1992) compiled measured streamflow data for 1659 stations with at least 20 years of complete records between 1874 and 1988. A streamflow data product similar to those described above will be produced for the GCIP EOP. A summary of the Surface and Ground Water Task is given in Task 10.8.1.




TASK TITLE -- 10.8.1 Surface and Ground Water

OBJECTIVE -- To provide the Surface and Ground Water data products from the USGS National Water Information System to the GCIP Data Management System.

PRODUCT DESCRIPTION -- The USGS compiles and indexes information on sites for which water data are available , the types of data available , and the organizations that store the data. The surface-water discharge data processed on a water-year basis is a very important data product needed for all the stations in the Mississippi River basin. Other types of data such as that available for lakes and reservoirs are also needed for water budget studies.

PROJECTED IMPROVEMENTS -- Improvements in computer facilities and database design will make these data more readily available through electronic means. Also, preliminary computations of discharge are being made available.

GCIP DATA SOURCE MODULE -- In-Situ (Contact: S. Williams)

SCHEDULE -- Preliminary data, when available within two months after the observation month. Finalized data are available within six to nine months after the end of the water year.

GCIP USER AVAILABILITY - - Preliminary data within two months after the observation month. Finalized data about nine months after the end of the water year.

RESOURCE SUPPORT -- Surface and Ground Water data products are contributed to GCIP by the USGS



10.9 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.

1997-1998 Activities

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

(i) Four to six flux towers should be located within the GCIP area. These will be sited on the basis of a land cover/climatological classification of the GCIP area, conducted well ahead of time, using AVHRR data among other sources. The flux towers should be located near the (monitoring) radiation rigs and should measure:

These measurements should be made throughout one experiment year, preferably 1996 or 1997.

(ii) Airborne eddy correlation
Eddy correlation aircraft (preferably twin engine aircraft like the NCAR King Air on the NAS/NRC Twin Otter) will be used during a series of Intensive Field Campaigns (IFC); perhaps three or four IFC's each of 10-20 days during the experimental year.

The aircraft will be used to conduct the following tasks:

These airborne eddy correlation data will be used to validate the large- scale application of surface-atmosphere flux calculation models forced by remote sensing data and meteorological observations or analyses.

(iii) Airborne soil moisture measurements

Aircraft equipped with gamma-ray or microwave sensors should be used to make soil moisture transect measurements. In some cases, these should be validated by a compact ground measurement exercise.

1999 Activities

The routinely-acquired satellite data and the combined surface observations/analysis fields of meteorological conditions will be used to drive regional scale models that will calculate continuous time-series fields of the following quantities:


Heat Fluxes: Momentum: Surface conditions:

10.10 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. These high resolution "soundings" 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 is now co-funding the procurement phase with the FAA.

1997 Activities

A competitive contract was awarded in July 1995 with FAA certification of the WVSS completed in 1996. After successful certification, six units will fly for two to three months each on a Boeing-757 aircraft. This activity will be a final confirmation that the data are of sufficient quality and that the sensing system operates unattended as expected before implementing contract options for 160 additional aircraft for the FAA and for GCIP.

Evaluation of the data will be performed by NOAA's Forecast Systems Laboratory (FSL) for 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 13. The 160 aircraft will provide approximately 640 ascent profiles per day. The similar number of descent profiles" are of a different form, and although not like a sounding, do provide additional information for 4DDA.

For the demonstration program in 1998 and 1999 United Parcel Service (UPS) will carry at least 22 units and the balance will be carried by American Airlines and other commercial carriers.

10.11 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. 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.