3-D effects in microwave radiative transport inside precipitating clouds: Modeling and applications

New rainfall techniques urge microwave physically based retrievals to produce an estimate error, to be more precise at the instantaneous level and to provide a correct geolocation of the raining areas. Within 3D structured clouds the coupling between horizontal and vertical inhomogeneity introduces additional uncertainties to instantaneous estimate because of the azimuthal dependence of the radiation field. In fact conical scanning microwave radiometers looking at the same point at the ground from different positions may measure quite different brightness temperatures. For radiometric scene over mirror surfaces, this 3D radiative effect, averaged over TMI-like footprint, can be fully described by 1D slant path models, except for strongly scattering highly developed raining cells at 85 GHz. A simulation radiative transfer study applied to Goddard Cumulus Ensemble Cloud Resolving Models, shows that the fore/after view configuration, now available for some new generation sensors, may help in capturing features like tilted or different stage raining cells, emission peaks, asymmetric ice decks, especially in convective regions. This definitely leads to a better insight in the slant path cloud properties and to an improvement of Bayesian technique driven rain retrievals