ABSTRACT
Accurate observation of global precipitation is important for water resource management, agriculture, hydrology, natural disaster monitoring and warning, weather forecasting, and climate study. Despite its importance, it is a dif†cult task since each common observational method has its own de†ciencies. For example, global rain gauges are sparse, particularly over ocean and underpopulated areas, and can also be affected by wind. Remote sensors receive signals from hydrometeors aloft that may evaporate or change location before reaching the ground. Global radar coverage is sparse. Only satellites can provide global coverage and can repeat frequently. Satellite sensors
11.1 Introduction .......................................................................................................................... 191 11.2 Physical Basis of Passive Millimeter-Wave Precipitation Retrieval .................................... 192
11.2.1 Thermal Radiation .................................................................................................... 192 11.2.2 Millimeter-Wave Interaction with Atmospheric Constituents .................................. 193
11.2.2.1 Millimeter-Wave Interaction with Hydrometeors ...................................... 193 11.2.2.2 Millimeter-Wave Interaction with Atmospheric Gases ............................. 194
11.2.3 Radiative Transfer Equation ..................................................................................... 195 11.3 Description of AMSU ........................................................................................................... 197 11.4 Physics Relating Precipitation Rate to Millimeter-Wave Radiance Spectra ........................ 198 11.5 Signal Processing Methods ...................................................................................................200
