A High-Resolution Hydrometeorological Forcing and Landscape Attributes Data Set for Hydrological Applications over the Southeastern United States

In anticipation of NASA's Global Precipitation Measurement (GPM) ground-validation activities the SE United States and synergies with NOAA's Hydrometeorology Testbed-Southeast Pilot Study (HMT-SEPS) in western North Carolina, a high-resolution data set is being developed to provide the Hydrologic Modeling community with common control forcing and landscape attributes to facilitate multi-scale, multi-purpose hydrologic modeling studies ranging from flash-flood forecasting to basin-scale water resource assessments. In the first phase of the project, the goal is to generate quality hydrometeorological forcing data sets at high spatial and temporal resolution (1km×1km, hourly time step) for the five-year time period 2007-2011 with a focus on the river basins with headwaters in the Southern Appalachians: Upper Tennessee River Basin (56,573 km2), Savannah River Basin (27,110 km2), Santee River Basin (39,862 km2) and Yadkin-Pee Dee River Basin (46,310 km2). For subsequent years, the data are updated on every three months. Space-time varying land surface properties such as broadband albedo, broadband emissivity, fractional vegetation coverage and leaf area index are derived from MODIS products. The original products are re-projected and composited to the study area, bilinearly interpolated to basin grids, and then linearly interpolated into hourly time steps from the nominal daily, 8 day or 16 day. Missing data gaps are addressed using physically meaning full constraints based on ancillary data. Precipitation is generated from NCEP/EMC 4KM Gridded Data (GRIB) Stage IV hourly data using the nearest neighbor method. Integration of Stage IV data with precipitation observations from research networks in the region provides dynamic relationships for improving precipitation accuracy in mountainous terrain. The atmospheric forcing data are extracted from North American Regional Reanalysis (NARR) products originally at 32-km spatial resolution and 3-hour temporal resolution. Elevation adjustments and corrections to near-surface variables are applied between NARR envelope terrain and local terrain at every time-step based on predicted atmospheric conditions (e.g. using dynamic lapse rates). Special bias corrections for downward shortwave radiation are applied through dynamical adjustment, accounting for localized elevation and topographic effects. The temporal interpolation for shortwave radiation is integrated in the topographic correction to capture the diurnal solar cycle and the evolution of illumination geometry over the complex terrain. Results of systematic evaluation of the data through analysis of water and energy budgets using a physically-based fully-distributed hydrological model over the Upper Tennessee River Basin are presented.