Precipitation Modeling for Inversion Purposes

Abstract

Precipitation retrieval from space which makes use of physical forward radiative transfer modeling requires the proper treatment of all sources of radiation scattering and emission in atmosphere, clouds. and interaction with surfaces. This involves the evaluation of the significance of individual effects with respect to the observed signals. In case of microwave radiation, these effects are the three-dimensional distribution of temperature, humidity, and hydrometeor concentrations, particle size distributions, and particle composition and shape. On the technical side of the problem, the accuracy of the radiative transfer model and the simulation of the radiometer's imaging specifications are important. Most of the above effects have been described in the past thus a certain background for the generation of retrieval databases from radiative transfer simulations is available. However, there are major drawbacks at the current state of precipitation retrieval: (1) even though individual radiation processes are well described, no synthesis is available combining the best available models; (2) the errors of radiative transfer in realistic clouds are unknown thus limit its use in numerical prediction models together with satellite data; (3) the input to the radiative transfer models, i.e., cloud and precipitation models seem insufficient for the application of retrievals beyond regional studies.