A revised geophysical model function for the advanced scatterometer (ASCAT) at NOAA/NESDIS

The current ASCAT winds retrieval is based on the CMOD5.n geophysical model function (GMF) with the ASCAT wind data processor developed at the Royal Netherlands Meteorological Institute (KNMI). Recent validation of ASCAT wind retrieval reveals that high wind retrievals were underestimated as being compared to the operational QuikSCAT scatterometer. The goal in this paper is to improve ASCAT wind retrievals at high winds. In this paper we map the radar backscatter (σ₀) as a function of extreme wind conditions as measured by an airborne scatterometer and adjusted the isotropic term in CMOD5.n to follow the aircraft GMF trend. The geophysical model QuikSCAT wind inputs are improved for σ₀ that calculated from QuikSCAT wind inputs are improved for σ₀ approximately > -15 dB and in very good agreement with the ASCAT σ₀ measurement. The wind retrieval validations show wind speed rms error is improved at approximately wind speed > 12 m/s and example mean wind composite from two winter seasons shows significant in detection of storm-force winds.