Deep cloud clusters in the tropics

Abstract

Deep cloud clusters (DCC) play an important role in the transfer of energy and moisture from the surface to the upper troposphere of the earth. The factors which govern the existence of DCC over oceanic regions have been examined by many investigators and they have shown that the necessary condition for the existence of DCC in oceanic regions is that the sea surface temperature (SST) must be above 28 C. In this paper the factors which govern the existence of DCC in both continental and oceanic regions has been examined. It has been shown that the necessary condition for the existence of DCC in continential (oceanic) regions is that the surface moist static energy must be above 350 kJ/kg (340 kJ/kg). The difference in the moist static energy threshold between the oceans and the continents has been attributed to the differences in the vertical profile of moist static energy. If the mean moist static energy of the troposphere from surface tu 400 millibar is used (instead of the surface moist static ,energy) then the threshold for the existence of DCC is 335 kJ/kg and is the  same for both oceans and continents. The total energy convergence in the troposphere has been shown to be an important constraint which could reduce the presence of DCC in the warmest oceans or continent. It has been shown that there can be several routes to desertification when vegetation is removed from a continental region.