The role of moist convection in the West African monsoon system - insights from continental-scale convection-permitting simulations

Predicting the West African monsoon (WAM) remains a major challenge for weather and climate models. We compare multiday continental-scale simulations of the WAM that explicitly resolve moist convection with simulations which parameterize convection. Simulations with the same grid spacing but differing representations of convection isolate the impact of the representation of convection. The more realistic explicit convection gives greater latent and radiative heating farther north, with latent heating later in the day. This weakens the Sahel-Sahara pressure gradient and the monsoon flow, delaying its diurnal cycle and changing interactions between the monsoon and boundary layer convection. In explicit runs, cold storm outflows provide a significant component of the monsoon flux. In an operational global model, biases resemble those in our parameterized case. Improved parameterizations of convection that better capture storm structures, their diurnal cycle, and rainfall intensities will therefore substantially improve predictions of the WAM and coupled aspects of the Earth system.