Spaceborne precipitation SAR (PSAR): characteristics of PSAR-measured rain-cell shift and its application to Doppler velocity estimation

摘要

Basic system design of Precipitation SAR (PSAR) based on the specification of the Ku-band radar onboard the GPM "core" satellite, increasing the antenna aperture to 5 m, shows that about 4-fold improvement in along-track resolution can be achieved in comparison with the real-aperture-based radar. Apparent rain-cell shift and the beam smearing caused by the spread of raindrop terminal velocity spectrum, inherent problems in PSAR, are quantitatively studied using disdrometer data. A disdrometer-bascd simulation is also performed to study characteristics of rain-cell shift estimated from along-track profiles of PSAR-measured rain echo and path-integrated attenuation, assuming a simple rain cell model. Possibilities of estimating some rain properties such as mean Doppler velocity is suggested. Finally various issues in the system development and usefulness of the PSAR are discussed.