On the Diurnal Cycle of Rainfall and Convection over Lake Victoria and Its Catchment. Part II: Meteorological Factors in the Diurnal and Seasonal Cycles.

The purpose of this article is to determine the meteorological factors controlling the lake-effect rains over Lake Victoria. Winds, divergence, vertical motion, specific humidity, convective available potential energy (CAPE), and convective inhibition (CIN) were examined. The local wind regime and associated divergence/convergence are the major factors determining the diurnal cycle of rainfall over the lake and catchment. The major contrast between overlake rainfall in the wet- and dry-season months is the vertical profile of omega. This appears to be a result of seasonal contrasts in CAPE, CIN, and specific humidity, parameters that play a critical role in vertical motion and convective development. Significance Statement: The results of this study suggest that local factors (the anabatic–katabatic flow and lake–land breezes) do not play a role in the seasonal contrast in the lake-effect rains. The major contrast between the dry and wet seasons is evident in the vertical profile of omega, which is stronger and extends higher in the atmosphere during the wet season. Atmospheric humidity is higher during the wet season, modifying the values of CAPE and CIN. By modulating omega, these determine the seasonal cycle of lake-effect rains. These results have implications for predicting changes in the lake that will occur under global warming. [ABSTRACT FROM AUTHOR]