Significant impacts of radiation physics in the Weather Research and Forecasting model on the precipitation and dynamics of the West African Monsoon

Abstract

Precipitation from the West African Monsoon (WAM) provides food security and supports the economy in the region. As a consequence of the intrinsic complexities of the WAM’s evolution, accurate simulations of the WAM and its precipitation regime, through the application of regional climate models, are challenging. We used the coupled Weather Research and Forecasting (WRF) and Community Land Model (CLM) to explore impacts of radiation physics on the precipitation and dynamics of the WAM. Our results indicate that the radiation physics schemes not only produce biases in radiation fluxes impacting radiative forcing, but more importantly, result in large bias in precipitation of the WAM. Furthermore, the different radiation schemes led to variations in the meridional gradient of surface temperature between the north that is the Sahara desert and the south Guinean coastline. Climate diagnostics indicated that the changes in the meridional gradient of surface temperature affect the position and strength of the African Easterly Jet as well as the low-level monsoonal inflow from the Gulf of Guinea. The net result was that each radiation scheme produced differences in the WAM precipitation regime both spatially and in intensity. Such considerable variances in the WAM precipitation regime and dynamics, resulting from radiation representations, likely have strong feedbacks within the climate system and so have inferences when it comes to aspects of predicted climate change both for the region and globally.