Development of Cloud Profiling Radar for EarthCARE

Global three-dimensional cloud distributions and their properties (liquid/ice phase, optical depth, drop sizes, etc.) are important information to estimate the earth radiation budget more precisely. The interactions between cloud particles and aerosols are also focused to improve accuracies of climate model. In order to meet expectations of scientists developing climate models for global warming problem, European and Japanese space agencies plan to launce a satellite called EarthCARE (Earth Clouds, Aerosols and Radiation Explorer) in 2012. A Cloud Profiling Radar (CPR) is installed on this satellite as a main sensor to observe clouds. Comparing with optical sensors, millimeter wave radar can penetrate upper thick clouds and observe cloud or rain layers below it. CPR has much sensitivity to cloud particles than meteorological weather radar, so CPR can detect most of radiatively important clouds in global region. Powerful effectiveness of CPR has been already displayed by CloudSat, which installs first millimeter wave radar in space. Following this success, CPR on EarthCARE is expected to bring new important information on various clouds on earth.

Comparing with CPR on CloudSat, CPR on EarthCARE will have better sensitivity to cloud detection. CPR is now designed to achieve about 10 dB better sensitivities with use of larger high gain antenna and lower satellite orbit. Other feature of CPR/EarthCARE is a Doppler function. CPR/EarthCARE will try to measure vertical Doppler velocity of cloud echoes, which are important for cloud physics and drizzle detection. Since the satellite will fly horizontally with very high speed, small speed detection of vertical speed of cloud is difficult task and challenging work.

CPR on EarthCARE is going to develop mainly in Japan side (NICT and JAXA) in cooperation with European Space Agency (ESA). In order to get better sensitivity and better Doppler accuracy, detail designs of the CPR are studied now. The latest consideration of CPR design will be introduced in this presentation.