The generally held assumption, that the bulk of tropical rain over the oceans is generated where the sea is warmer than the air, is being largely verified in this article with the new tool of satellite cloudiness mapping. The discussion focuses on the satellite-observed variable position of the boundary between the west Pacific equatorial rain clouds over warm ocean water and the east Pacific aridity along the equator over cool upwelling water. The often quite abrupt changes between these two regimes in the mid-Pacific are known from an eighteen-year sequence of ocean and atmosphere data at Canton Island. This article describes the same phenomena delineated by satellite television data recorded during 1962–67, and adds features of the geographic cloudiness distribution not obtainable from the widely spaced fixed points of observation.

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A selected group of 1973 North Pacific Ocean tropical cyclones was studied by using data from the Nimbus 5 Electrically Scanning Microwave Radiometer (ESMR), the Temperature-Humidity Infrared Radiometer (THIR), NOAA-2 and USAF DMSP imageries. From the unique combination of infrared, visible, and microwave data, it was possible during various stages of storm development to differentiate between dense cirrus outflow and rain areas, to identify centers of circulation and areas of low-level moisture, and by the use of a theoretical model to estimate semi-quantitatively areas of light, moderate, and heavy rainfall rates.

Mid-tropospheric circulation features under essentially clear sky conditions have been noted in the data of the 6.7 /am channel of the Nimbus 4 Temperature-Humidity Infrared Radiometer (THIR) while at the same time these features were undetected by the 11.5 /mi channel of the same instrument. The characteristic response of the 6.7 /am channel to atmospheric water vapor emission is primarily from the 250-mb (10.5 km) to 500-mb (5.5 km) levels with a peak contribution at 350 mb (8 km). Dry and moist patterns seen in the 6.7 ^m data on 21 February 1971 have been integrated into a 400-mb moisture analysis over the United States. This analysis provided more detailed and timely information than was conventionally available about the advection of dry air aloft prior to development of the Mississippi Tornado of February 1971. The derivation of middle to upper atmosphere flow patterns from the Nimbus 4 THIR, 6.7 ^m data under cloud-free conditions has a direct application on a global scale for the GARP and World Weather Watch Programs.