Abstract
Radars have played an important role in the observation of precipitation and will continue to do so in the future. With the recent introduction of space-based radar for measuring precipitation on the Tropical Rainfall Measurement Mission (TRMM) satellite, weather radar applications now range from local to global scales. The radar basis for characterizing precipitation lies in the scattering and propagation properties of electromagnetic waves through precipitation, and is summarized in this paper. The methodologies for converting the backscattering and propagation measurements such as radar reflectivity, differential reflectivity, differential propagation phase, and attenuation to precipitation estimates are provided for both ground-based and space-based radars. Quantitative precipitation estimation has been a challenging problem for over four decades. This challenge has inspired extensive progress in the area of precipitation microphysics, remote sensing techniques, and in situ observations. Another major advance in quantitative precipitation estimation is the understanding of the critical role player by practical engineering considerations. Techniques for developing precipitation algorithms from space and ground observations as well as strategies for validating the estimates are also presented. Following a summary of the various challenges, the discussion focuses on those areas with potential for significant future progress for the estimation of both local and global precipitation.
