Simulation of the Stokes vector in inhomogeneous precipitation

The large absorption and scattering cross sections of liquid and frozen hydrometeors, respectively, introduce appreciable signatures to measured polarized brightness temperatures, degrading the retrieval of other geophysical parameters such as near-surface ocean winds. In particular, the retrieval of wind direction requires precise knowledge of polarization. This study investigates the fully polarized atmospheric contribution of precipitation and compares these effects with the current sensitivities of passive wind vector retrieval algorithms. A realistic microphysical cloud model supplies atmospheric parameters, including hydrometeor water contents, which are input into a vector radiative transfer model. Scattering is handled using a reverse Monte Carlo method. Radiances are simulated for three frequencies of interest to microwave polarimetry, 10.7, 18.7, and 37.0 GHz, for the four elements of the Stokes vector. The simulations show that the dichroic nature of precipitating media has a significant impact on passive wind vector retrievals.