Cloud and Precipitation Observation by Spaceborne Radar in Japan: Current and Future Missions

The Tropical Rainfall Measuring Mission (TRMM) is a Japan-US joint satellite mission which equips the world first spaceborne precipitation radar (PR) as well as microwave imager (TMI) and has been producing very valuable precipitation data more than twelve years. This long term precipitation record including vertical profile information from the TRMM PR made it possible to provide not only the precise global precipitation amount but also improve the understanding tropical cyclones such as typhoons and hurricanes and diurnal cycles of rainfall. It is worth to note that the precipitation climatology developed from the PR data has been used to evaluate Global Climate Models for the prediction of the climate change and the global cloud resolving model such as NICAM. The follow-on mission of the TRMM which is called the Global Precipitation Measurement (GPM) mission is planned to be launched in 2013. The GPM mission consists of the Core satellite which equips dual frequency (14 GHz and 35 GHz, the former is same frequency as the TRMM/PR) radar to improve the estimation accuracy of rainfall and to observe the light rain and snowfall and constellation satellites which equip microwave radiometer to gain the sampling of precipitation. Satellite cloud remote sensing started with optical sensors to estimate cloud characteristics such as the effective radius. In 2006, NASA’s CloudSat satellite was launched to observe the cloud using 95-GHz cloud radar. CloudSat has been providing the vertical structure of clouds and even light rain and enables us to see the cloud and precipitation properties at the same time. In Japan, spaceborne cloud radar similar to the CloudSat but upgraded in terms of sensitivity, long life time and the additional Doppler capability is being developed for EarthCARE mission which is a JAPAN-ESA joint program aiming to reveal the aerosol-cloud processes, to realize more precise Earth radiation budget estimation using cloud radar and lidar (laser radar), and to improve future predictions of the global warming. * Corresponding author. Riko Oki, Earth Observation Research Center, Japan Aerospace Exploration Agency.