A new method for analyzing the attenuation characteristics of satellite radar altimeter signals due to rainfall based on a multilayer medium model

Rainfall has an attenuation of backscatter coefficient of the sea surface and a change in the sea surface roughness, and these effects give rise to some errors in retrieving the sea surface wind speed, the significant wave height, and wave slope. It is meaningful to make considerable efforts to study the attenuation of radio waves caused by rainfall. In this article, a new model of analyzing the attenuation characteristics of satellite radar altimeter pulse signals because of rainfall is presented. First, the model of the equivalent permittivity of rainfall is calculated and presented. The imaginary part of the equivalent permittivity is studied when radio frequency and rainfall rate vary, respectively. Second, a new theoretical model and method of analyzing the effect of rainfall on satellite radar altimeter pulses is presented based on a multilayer-medium model with the equivalent permittivity of rainfall. On the other hand, some existing models of computing rainfall attenuation characteristics of radar signals are studied and improved to some extent. Finally, some attenuation characteristics of radar signals due to rainfall are calculated by those models. The calculated results show that the attenuation characteristics of radar altimeter pulse signals are all in good agreement with those by other models. The results computed by the multilayer-medium model can provide a good theoretical explanation and understanding for these attenuation characteristics of radar pulse signals and can also give some data support and corrections for the measured oceanic parameters by the satellite radar altimeter.