Presenting Author: Dr. Thomas Meissner

We have developed algorithms that retrieve ocean surface wind speed and direction under rain using brightness temperature measurements from passive microwave satellite radiometers. For accurate radiometer retrievals of wind speeds in rain it is essential to use brightness temperature signals at different frequencies, whose spectral signature makes it possible to find channel combinations that are sufficiently sensitive to wind speed but little or not sensitive to rain. The wind speed retrieval accuracy of an algorithm that uses C-band frequencies and is trained for tropical cyclones ranges from 2.5 m/s in light rain to 3.5 m/s in heavy rain. We have also trained and tested a global algorithm, that is less accurate but can be applied under all conditions. Its estimated accuracy is between 2.5 m/s in light rain and 5.5 m/s in heavy rain. The wind direction retrieval accuracy degrades from about 10o in light rain to 25o in moderate – heavy rain. We compare the performance of wind vector retrievals under rain from microwave radiometers with those from scatterometers and discuss advantages and shortcomings of both instruments. We also analyze the wind induced sea surface emissivity including its wind direction dependence at high wind speeds up to 40 m/s, which are generally only present under rain.

2025 International OVWST Meeting May 5th - 8th Darmstadt, Germany

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