RAINFALL OBSERVATION FROM SPACE - APPLICATIONS OF TROPICAL RAINFALL MEASURING MISSION (TRMM) AND GLOBAL PRECIPITATION MEASUREMENT (GPM) MISSION

摘要

Satellite observation is a unique and effective tool to cover a large area homogeneously in a short time. In this paper, we introduce two missions for rainfall observation, i.e., the Tropical Rainfall Measuring Mission (TRMM) and the Global Precipitation Measurement (GPM) mission. The TRMM satellite is the first satellite mission focused on rainfall observation. TRMM is a joint mission between Japan and the U.S. and was launched in November 1997. The TRMM carries the world's first satellite-borne Precipitation Radar (PR) developed by Japan, in addition to instruments, such as an infrared imager and a passive microwave imager (TRMM Microwave Imager; TMI). The combined use of PR and the TMI has greatly improved the estimation of rainfall amount. It has also revealed the three-dimensional structure of tropical cyclones over the ocean, which was rarely observed before the TRMM satellite. More than 12 years after the satellite's launch, it continues to perform excellent observations and provide valuable meteorological and climatological data relating to precipitation. Currently, the GPM mission, led by Japan and the U.S., is scheduled under international collaboration. One major characteristic of the GPM mission as follow-on and expansion of the TRMM satellite is operation of the GPM core satellite, which will carry dual-frequency precipitation radar (DPR) and a passive microwave radiometer, with a non-sun-synchronous orbit as a "calibrator" to other satellites. The other is its collaboration with a constellation of several other satellites developed by each international partner (space agency), each of which will carry passive microwave radiometers and/or microwave sounders, to increase observation frequency. The TRMM satellite focused on observation of the tropics, and the GPM mission will cover broader areas including high latitudes.