during the April to September 1995 Enhanced Seasonal Observing Period (ESOP-95) and include surface data from a variety of federal and state agencies, upper-air data, radar data, land characterization data, satellite data, and model output data. Additional ESOPs are being planned as GCIP emphasis moves from LSA-Southwest toward LSA-North Central, LSA-East, and eventually LSA-Northwest. The types of ESOP data gathered and disseminated will vary depending on data availability and needs within LSAs. For example, snow depth and areal extent measurements will be a special emphasis of the north central ESOP.
Most of the GIDS-4 data were collected by the University Corporation for Atmospheric Research (UCAR) Joint Office for Science Support (formerly known as the Office for Field Project Support) from existing data collection systems, although several unique data sets were derived from or supplement standard data (e.g., GIDS hourly and daily composites of precipitation and surface observations). ESOP-95 was also coordinated with the VORTEX project, and project data from both initiatives are available to all researchers. This combined data collection exemplifies the character of the climatological GCIP effort; GCIP is not planning specific field campaigns but instead intends to augment the GCIP continental and climatological perspective with data from individual field programs. Especially noteworthy is the successful cooperative data arrangement with the DOE's Atmospheric Radiation Measurement program, which will be included in the standard and LSA-SW ESOP data sets compiled for GCIP.
The GCIP Reference Data Set (GREDS) has been widely disseminated. GREDS includes a considerable amount of relevant background information, broadly characterized as data that will change little if at all during the next several years. This includes information on the physical geography of the GCIP region, along with cartographic information. GCIP is supporting additional efforts for characterizing soil physical and hydraulic properties. A soils data set is being developed from the U.S. Department of Agriculture (USDA) National Resource Conservation Service (NRCS) State Soil Geographic Database (STATSGO) and the county-level Soil Survey Geographic Database (SSURGO). This data set covers the 48 conterminous United States at a resolution of 1 km and contains information on texture, depth to bedrock, particle size distribution, rock fragment class and volume, porosity, hydrologic soil groups, and available water capacity. These data sets not only are useful to GCIP but also are useful to a wide variety of interdisciplinary studies.
Another retrospective data project being developed consists of pertinent data from two abnormal climatic events, the 1998 drought and the 1993 floods in the Mississippi River basin, which occurred just as GCIP was beginning its data collection efforts. These data will be used in conjunction with regional modeling efforts designed to understand these extreme events. Future data projects will include compiling high-quality hydrometeorologic data for even longer time periods (e.g., 30 years) to put ESOP and Enhanced Observing Period (EOP) data in their climatologic context and to assess the impact of climate variability on water