The development of a C-band Advanced Scatterometer (ASCAT) geophysical model function at NOAA/NESDIS

Validation of the ASCAT wind vectors show that the ASCAT wind speed errors are within 2 m/s RMS error for wind speeds up to 15 m/s, however they exhibit and increasing low bias beyond 15 m/s. An examination of the ASCAT ¿⁰ revealed some additional sensitivity at the higher wind speeds that was not adequately represented by the current geophysical model function (GMF). A revised GMF is empirically derived using a near-real-time QuikSCAT as a surface truth. A new DC term in the GMF is derived and replaced in the operational CMOD5.5 GMF. Validation of the revised GMF shows that the wind speed retrievals are closer to QuikSCAT for wind speeds > 15 m/s than the operational retrievals, while wind direction retrievals remain the same for all wind speeds as expected.