Rainfall is major driving force of the global water and energy circulation.
In the PR, swath width of 215 km is achieved by using an active phased array technique. Measurement of rain by PR, TMI, and VIRS PR, TMI, and VIRS are sensors for measuring the rain. PR and TMI, which can directly see the rain through cloud, are primary instruments for quantitative rain measurement. TMI has a wide swath and can make quantitative rain measurement over ocean. VIRS provides the information of cloud height and properties.