SEA SURFACE TEMPERATURE AND RAINFALL DELIVERY DURING THE DRY-WET TRANSITION MONTHS IN THE COASTAL BELT OF WEST AFRICA

Abstract

The interaction between the atmosphere - ocean results in the exchange of heat, momentum and water vapour, through latent heat flux, sensible heat flux, and radiation. Atmospheric humidity is a key variable in determining the geographical distribution and maximum intensity of precipitation, potential maximum intensity of tropical cyclones, human heat stress, biosphere and surface hydrology. This study examined the impact of sea surface temperature and the role of vertical velocity at 700hpa and relative vorticity at 500hpa on atmospheric moisture build up during the dry-wet transition months of January-April. A 30 years data of sea surface temperature, precipitable water, rainfall, relative vorticity at 500hpa, vertical velocity at 700hpa, maximum moisture depth (Hmax), maximum magnitude of zonal and meridional wind (Umax, Vmax) over 5 locations in the coastal belt of West Africa was used to investigate rainfall delivery. The sea surface temperature between 299.2- 302.9K was found to enhance the supply of precipitable water to locations in the longitudinal east as the easterly wind brings in moisture. This study also revealed that huge rainfall delivery in a coastal location is a function of sea surface temperature, positive relative vorticity at 500hpa and negative vertical velocity at 700hpa.Therefore sea surface temperature, longitudinal location, maximum moisture depth (Hmax), maximum magnitude of zonal wind (Umax), relative vorticity at 500hpa, and vertical velocity at 700hpa are all important parameters to consider for moisture build up during the transition months of January-April over the coastal station of West Africa.