Rain Mitigation for OSCAT Using a Rain Geophysical Model Function

Scatterometers are designed to measure the normalized radar backscatter (σ
^o
) of the ocean surface. Wind-only Geophysical Model Functions (GMF) are used to relate the σ
^o
to the near surface Wind Vector (WV), wind direction and speed. Rain alters the relationship between WV and σ
^o
captured in the wind-only GMF. Making a GMF that encapsulates the rain effects on σ
^o
lowers the error between retrieved WV and actual measured WV.The Ocean Scatterometers (OSCAT-1 and -2) are a Ku-band dual beam scatterometers that operated from 2009-2021. To create a rain GMF OSCAT is collocated with Tropical Rain Measurement Mission (TRMM) rain measurements and European Centre for Medium-Range Weather Forecast (ECMWF) model winds. The rain GMF is created using a simple phenomenological rain model that relates σ
^o
in the presence of rain to surface wind-induced roughness. The Simultaneous Wind and Rain (SWR) algorithm uses the conventional wind-only GMF injunction with the rain GMF to estimate WV from σ
^o
.