The LDAS data set contains 43 model and observation-based fields produced by the LDAS uncoupled modeling system at the NASA Goddard Space Flight Center using the Mosaic Land Surface Model (LSM). Parameters include snow cover, snow depth, snow melt, albedo, precipitation, temperature, canopy characteristics, longwave and shortwave radiation, heat flux, soil moisture, sublimation, snow water ... equivalent, and meteorolical parameters. Precipitation and solar radiation are observation-based, while other forcing variables (humidity, temperature, wind speed, pressure, longwave radiation) are derived from the National Centers for Environmental Prediction’s (NCEP) Eta Data Assimilation System (EDAS). All other variables in the files are from the Mosaic LSM. Data were produced at an hourly resolution from 1 January 2001 through June 2003. The LDAS data are delivered on an 1/8th-degree regular latitude/longitude grid covering the Large-Regional Study Area (LRSA), located between 38.5-42 N and 104-108.5 W. The resolution in the Y direction of each 1/8th degree LDAS pixel is 13899 meters over the whole domain. The resolution in the X direction ranges from 10878 meters at the southern edge of the LRSA to 10329 meters at the northern edge of the LRSA (it decreases as the distance between longitude lines decreases). This data set is available in ASCII format from the Land Data Assimilation Systems (LDAS) at NASA's Goddard Space Flight Center (http://ldas.gsfc.nasa.gov/). Two sample FORTRAN programs are provided for reading these ASCII gridded data. The NASA Cold Land Processes Experiment (CLPX) is a multi-sensor, multi-scale experiment that focuses on extending a local-scale understanding of water fluxes, storage, and transformations to regional and global scales. Within a framework of nested study areas in the central Rocky Mountains of the western United States, ranging from 1-ha to 160,000 km2, intensive ground, airborne, and spaceborne observations are collected. Data collection focuses on two seasons: mid-winter, when conditions are generally frozen and dry, and early spring, a transitional period when both frozen and thawed, dry and wet conditions are widespread.