ABSTRACT
The former accelerates the atmospheric gases towards the earth’s surface, so that they exert a pressure upon the surface. In the northern hemisphere winter surface north-easterlies are dominant over most of West Africa. Over West Africa in the northern hemisphere winter net radiation levels are generally below 225 langleys and albedos are high. With the advancing sun comes a rise in net radiation and surface air temperature in northern West Africa. Towards the middle of the year with the continuing advance of the maritime airmass from the south, so the baroclinic and barotropic gradients from south to north across West Africa increase and the upper easterlies become the Easterly Tropical Jet. With rising air temperatures in West Africa comes a replacement of surface high pressure conditions by low pressure relative to that over the Gulf of Guinea. Deflection of the air movement to the right produces a clockwise circulation of the air out of the anticyclone.
