Foundations for statistical-physical precipitation retrieval from passive microwave satellite measurements. Part II: emission-source and generalized weighting-function properties of a time-dependent cloud-radiation model

Abstract

We first develop the theory needed to interpret the vertically distributed radiative sources and the emission-absorption-scattering processes responsible for the behavior of frequency-dependent top-to-atmosphere brightness temperatures TB's. This involves two distinct types of vertical weighting functions for the TB's: an "emission-source weighting function' describing the origin of emitted radiation that eventually reaches a satellite radiometer, and "generalized weighting function' describing emitted-scattered radiation undergoing no further interactions prior to interception by the radiometer. The weighting-function framework is used for an analysis of land-based precipitation processes within a hail-storm simulation originally described in Part I. The individual roles of cloud drops, rain drops, graupel particles, ice crystals, and snow aggregates - as well as absorbing gases, the earth's surface, and cosmic background - on generating and modulating the frequency-dependent TB's are examined in detail. Finally, a summary of the various components of a hybrid statistical-physical rainfall algorithm used to produce liquid-ice profile information, as well as surface rain rates, is given. The algorithm employs the cloud model to provide a consistent and objectively generated source of detailed microphysical information as the underpinnings to an inversion-based perturbative retrieval scheme. -from Authors