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This note is intended to serve primarily as a reference guide to users wishing to make use of the Tropical Rainfall Measuring Mission data. It covers each of the three primary rainfall instruments: the passive microwave radiometer, the precipitation radar, and the Visible and Infrared Radiometer System on board the spacecraft. Radiometric characteristics, scanning geometry, calibration procedures, and data products are described for each of these three sensors.

The spatial and diurnal variation of rainfall over Asia was investigated using the spaceborne radar data for four seasons during 1998–2003. The regional variation of the prevailing precipitation systems most closely associated with the maximum hourly rainfall was shown by examining the fine spatial distribution of rainfall amount and scale‐based precipitation systems. Small precipitation systems (<102 km2) occurred most frequently around early afternoon over most land. The south facing slopes of the Himalayas, especially south of Mount Everest and the upper portion of the Brahmaputra valley, is the most obvious region of the daytime genesis of the convective systems over the Asian landmass. Over the Tibetan Plateau the occurrence of the small systems was larger than over inland India and the foothills. Large systems (>104 km2) developed mostly in the evening over nearly flat landmasses. Wide‐spread systems with intense rain pixels developed over the foothills of the Himalayas in late night–early morning period, which was distinct from the daytime convection. Over ocean, in addition to the morning signature, spatially inhomogeneous and systematic characteristics were evident over the offshore region, for example, around the maritime continent. Large systems, which are strongly associated with terrain, have a great influence on the total number of rain pixels and the total amount of rainfall. For 86% of the region where large system is dominant the time of maximum rainfall is within 3 hours of the time of maximum rainfall for large systems.

Observations from the precipitation radar aboard the Tropical Rainfall Measuring Mission satellite provide the first opportunity to map vertical structure properties of rain over the entire Tropics and subtropics. Storm height histograms reveal a distinct bimodal distribution over the oceans with the lowest mode near 2 km and the upper mode at 5 km. The low mode is the dominant feature over regions previously associated with precipitating marine stratocumulus/stratus and trade wind cumulus. In those regions a lognormal distribution fits the observed storm height distributions quite well, and a strong correlation exists between conditional mean rainfall rate and storm height. In addition, the low mode appears within the major tropical convergence zones associated with significant precipitation, and in those regions a mixed lognormal distribution is used to separate the storm height distribution into two parts: shallow and deep. In this exploratory analysis, the correlation between rainfall intensity and storm height is used in combination with the mixed lognormal distribution to estimate that shallow precipitation composes approximately 20% of the total precipitation over tropical oceans during both El Nin ˜o and La Nin ˜a conditions.

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