Microwave emission properties of a precipitating atmosphere with respect to remote sensing of precipitation from space by means of microwave radiometry

The study of precipitation at the observation of the Earth from space is one of the important problems of remote sensing. For the first time the possibility of estimation of rain intensity by upwelling Earth radiation was shown by the experiment conducted on the satellite "Kosmos-243" in 1986. Areas of precipitation falling over sea surface were registered by typical emission of brightness temperature at wavelengths of 0.8, 1.35 and 3.2 cm. By the magnitude of emission several rain intensity levels may be distinguished. Further development of precipitation observation from space is related with American satellite DMSP with microwave radiometric system SSM/I, which received radiation in a wide range of wavelengths from 0.35 to 1.6 cm. This system made it possible to carry out the study of precipitation fields over the surface and sea. The precipitation in radiometric images appeared as areas with lower brightness temperature at 0.35 cm wavelength. This is accounted for by the increase of the Earth albedo due to multiple microwaves scattering on large rain drops. Over recent years the remote sensing of precipitation was conducted on Japan-USA satellite TRMM. A large project GPS (Global Precipitation Mission) is under preparation.