Mean cloud distributions over tropical oceans

The paper suggests that mean cloud distributions over tropical coeans as revealed by satellites may be intimately related to distributions of mean ocean surface temperature. From a qualitative consideration of the atmosphere's response to the underlying ocean surface temperature through energy exchanges, formation of clouds in a moving airmass over cold and warm oceans is discussed and illustrated with specific examples from the Indian ocean. It is shown that when warm air moves over a cold ocean, there is little or no formation of clouds. In the case of cold air moving over a warm ocean, there is gradual transformation of clouds from stratified to cellular type and development of cloud cells and cloud groups in the warmer parts of the ocean. Randomly distributed large cloud masses or ensembles known as cloud clusters appear to form over warm equatorial oceans. The intertropical convergence zone which is located in the region of maximum ocean surface temperature appears to be characterised by a band of cloud clusters. Occasionally, two separate cloud bands may be seen in near-equatorial waters, one in each hemisphere. Formation of two prominent cloud bands in the southern hemisphere is discussed. Finally, an examination of the mean rainfall distribution over tropical oceans suggests that it may be related to distribution of mean ocean surface temperature in much the same way as the mean cloud distribution.