Some Examples of Rapidly Growing Oceanic Cumulonimbus Clouds

Abstract

Infrared satellite photographs of the tropical oceanic regions within and around the GATE A/B array point to the existence of large, rapidly growing, cumulonimbus clouds. The region along 10°N experiences the greatest frequency of these storms. Also a pronounced diurnal variation is found in the times of initial development with maximum frequencies near midnight. In most cases, this anvil cloud grows to an areal extent ?7000 km2 in about 4 h, then dissipates in another 3 h. The velocity divergence in the anvil is 1?3?10?4s?1 and the mass outflow is 100?200 kton s?1. These storms account for some of the difference in diurnal variation of high cloudiness that is observed between tropical oceanic and continental regions. A large number of rapidly growing cumulonimbus clouds was observed on 10 August 1974 in connection with a disturbance in the tropical easterlies that ultimately developed into Tropical Storm Alma.