Forcing Data and Hydrological Parameters

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Datasets Description 

Soil hydraulic parameters (i.e. saturated hydraulic conductivity, porosity, field capacity and wilting point) were extracted in ArcGIS from the STATSGO database. The values for the vertical the top 11 standard soil layers in STATSGO are provided.  The standard soil layers defined in STATSGO are given in Table 2. Space-time varying land surface properties such as broadband albedo, broadband emissivity, fractional vegetation coverage and leaf area index are derived from MODIS products (Table 3) . The original products are re-projected and composited to the study area, bi-linearly interpolated to basin grids, and then linearly interpolated into hourly time steps. Quality-control and temporal filtering for these landscape attributes data are performed to reduce the discontinuity caused by cloud contamination. The atmospheric forcing data are extracted from the 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 local diurnal solar cycle based on solar zenith angle. Precipitation is generated from NCEP/EMC 4KM Gridded Data (GRIB) Stage IV hourly data using bi-linear interpolation and orographic corrections. Integration of Stage IV data with precipitation observations from research networks in the region provides dynamic relationships for improving precipitation accuracy in mountainous terrain.

Table 1 Summary of the datasets (N=Row, M=Col, T=Time step)

Table 2 Soil layers defined in STATSGO

Table 3 Summary of the MODIS Products used in this project