The CP4 Africa Control Simulation—An Initial Assessment of the Run

A convection-permitting (4.5km at the equator) regional climate simulation (CP4-Africa) using the Met Office Unified Model has been run for the first time on an Africa-wide domain. The model has been run as part of the Future Climate for Africa (FCFA) IMPALA (Improving Model Processes for African cLimAte) project. The CP4-Africa simulation is driven by an AMIP style N512 (~26km in latitude and 39km in longitude at the equator) global model using a convective parametrisation scheme for the period 1997-2006. A 10 year, non-convection permitting regional model (nCP25-Africa, same resolution as the global model) regional model covering Africa with identical high time (i.e. hourly) output has been run for comparison with the CP4-Africa simulation. The latest progress of the CP4-Africa simulation will be presented together with a brief description of the models.

An initial assessment of the CP4-Africa simulation comparing with the nCP25-Africa regional model shows many benefits particularly when looking at fields influenced by convection. The sub-daily variation of precipitation is improved, with the diurnal peak in rainfall being later in the day in better agreement with observations. The CP4-Africa run has a better distribution of 3 hourly precipitation values than the nCP25-Africa model. While some seasonal mean biases in CP4 are reduced relative to the nCP25-Africa model others are increased. There is a large change in the simulation of cloud, with CP4-Africa having far more cloud ice and cloud water than the nCP25-Africa. This alters various top of atmosphere radiation biases from one sign to other.