Statistical study of ground base cloud radar for developing algorithm of EarthCAER Cloud Profiling Radar

A satellite called EarthCARE (Earth Clouds, Aerosols and Radiation Explorer) is planning to launch in 2015. A W-band Cloud Profiling Radar (CPR) is installed on this satellite and one of the features of CPR/EarthCARE is a Doppler measurement function. This is the first trial to measure the vertical Doppler velocity from space, so there are many issues on Doppler measurement accuracy. Since the satellite will fly horizontally with very high speed, small speed detection of vertical speed of cloud is difficult task and challenging work. Other issue is Doppler folding correction. In order to keep some observation range, pulse repetition frequency is limited. Then, the maximum Doppler velocity is also limited and Doppler folding is unavoidable for large speed echoes, such as large rain drops. For example, in order to keep 20 km observation range, maximum PRF is limited in 6100-6600Hz and Doppler folding are arose over 4.8-5.2m/s velocity. In order to develop Doppler unfolding algorithm for EarthCARE/CPR, we need to check how frequent Doppler folding occur from ground-base observations. We will show statistical study of ground-base cloud radar observation in this presentation and propose some algorithms for Doppler unfolding.