ИСТИНА

Passive microwave sounding is a very effective and commonly applied technique for investigation of atmospheric precipitation from space. Progress in this field is largely related to the experiment SSM/I within DMSP project. Sounding was performed on several frequencies within 19 - 85 GHz band from the 833 km high polar sun-synchronous orbit. Results of these measurements have been involved in many published research. As it is known, typical signature of raining atmosphere in the microwave band is its dichroism due to non-spherical shape of falling rain drops. Polarization of both thermal radiation and radar echoes is determined by this dichroism. Most applied theoretical model of this situation is a homogeneous flat slab medium. Atmospheric clouds, and therefore rain fields, are typically spatially ingomogeneous (the so-called broken clouds). In practice, rain field consists of separate rain cells of several kilometers size. Numerical simulations of radiative transfer in such cell is very complicated in comparison with flat layered slab medium. In the present work, numerical results of computer simulations of thermal radiation in the flat layer, 2D and 3D rain cell are presented. Radio brightness temperatures for vertical and horizontal polarization are assessed. I has been shown that the 2nd Stokes parameter Q (difference between vertical and horizontal poalrization) can reach up to 3-5 K, which is enough for reliable identification of rain with space-borne microwave radiometer. Specifications of the orbital interferometric radiometer necessary for detection and estimation of isolated rain cells are discussed.