Seasonal variations in the diurnal patterns of convection in Cameroon–Nigeria and their neighboring areas

Abstract

Abstract High‐resolution (5‐km, 30‐min) Meteosat 7 infrared images are used to document seasonal variations of the diurnal cycle of convective activity over Cameroon and Nigeria during the period 1998‐2002. Cloud fraction, considered to diagnose the properties of cold clouds, is derived by using a threshold of brightness temperatures less than 235 K, thus providing a detailed view of regional differences in the diurnal patterns. The features of the diurnal cycle of convection were investigated for six sampled regions. Over land, the diurnal cycle of convection is mainly controlled by the radiative heating and associated low‐level destabilization. Strong spatial variations exist in the seasonal amplitude of diurnal cycle, highlighting that complex orography, land‐sea contrast and coastline curvature play an important role in modulating the spatial and diurnal patterns of convection. There is consistent noon diurnal peak without obvious seasonal variations of the phase over the ocean. Copyright © 2010 Royal Meteorological Society