A Proposed Tropical Rainfall Measuring Mission (TRMM) Satellite

TLDR

The TRMM mission aims to map monthly precipitation and latent‑heat release over ~105 km² areas to improve short‑term climate and global circulation models and to better understand tropical oceanic rainfall variability. TRMM will carry the first quantitative spaceborne weather radar, a multichannel passive microwave radiometer, and an AVHRR aboard a ~320 km low‑inclination orbit, enabling twice‑daily sampling of tropical regions and validation through ground‑based calibrated rain radars and advanced radiative‑cloud dynamical algorithms. Progress includes summarized mission goals, development of rain‑retrieval algorithms, and ongoing testing of these algorithms with high‑altitude aircraft microwave instruments over convective systems calibrated by ground radars.

Abstract

The Tropical Rainfall Measuring Mission (TRMM) satellite is planned for an operational duration of at least three years, beginning in the mid-1990's. The main scientific goals for it are to determine the distribution and variability of precipitation and latent-heat release on a monthly average over areas of about 105 km2, for use in improving short-term climate models, global circulation models and in understanding the hydrological cycle, particularly as it is affected by tropical oceanic rainfall and its variability. The TRMM satellite's instrumentation will consist of the first quantitative spaceborne weather radar, a multichannel passive microwave radiometer and an AVHRR (Advanced Very High Resolution Radiometer). The satellite's orbit will be low altitude (about 320 km) for high resolution and low inclination (30° to 35°) in order to visit each sampling area in the tropics about twice daily at a different hour of the day. A strong validation effort is planned with several key ground sites to be instrumented with calibrated multiparameter rain radars. Mission goals and science issues are summarized. Research progress on rain retrieval algorithms is described. Radar and passive microwave algorithms are discussed and the use of radiative models in conjunction with cloud dynamical-microphysical models is emphasized especially. Algorithms are being and will continue to be tested and improved using microwave instruments on high-altitude aircraft overflying precipitating convective systems, located in the range of well-calibrated radars.