Improved Sacramento Soil Moisture Accounting model calibrations from bias-corrected NEXRAD radar based precipitation estimates

The NOAA/NWS Ohio River Forecast Center (OHRFC) utilizes the Sacramento Soil Moisture Accounting (SAC-SMA) model for real-time hydrologic forecast operations, both for short lead-time deterministic forecasts and for Advanced Hydrologic Prediction Services (AHPS) Ensemble Streamflow prediction (ESP) 90-day probabilistic streamflow forecasts. Consequently, it is necessary to have well-calibrated SAC-SMA model implementations with minimal biases. Analyses of OHRFC Stage3/MPE NEXRAD radar based precipitation data from 1997-present show considerable bias at monthly, seasonal, and annual time scales.

Utilizing techniques developed at the NWS Office of Hydrologic Development (OHD), Hydrology Laboratory, based on the Parameter-elevation Regressions on Independent Slopes Model (PRISM) monthly historical data, bias corrections were made to the OHRFC archived Stage3/MPE precipitation data from 01/1997 to 08/2010. Independent automatic model calibrations using the Shuffle Complex Evolution (SCE) optimizer were made for several basins in the Ohio River Valley for both the bias-corrected and uncorrected Stage3/MPE precipitation data. Final calibration statistics show marked improvement using the bias-corrected Stage3/MPE precipitation data over the uncorrected Stage3/MPE precipitation data calibrations.