Regional model simulations of African wave disturbances


  • Leonard M. Druyan,

  • Matthew B. Fulakeza,

  • Wassila Thiaw


A regional climate simulation model is run at 50 km horizontal resolution over West Africa to study synoptic systems, such as African wave disturbances (AWDs). The study examines the results of 18 simulations, the longest of them covering the period August 8–15, 1988. Simulations were initialized with European Center for Medium-Range Weather Forecasts (ECMWF) gridded analysis data which also supply the lateral boundary conditions. Daily means of 700 mbar circulation and other model diagnostics are compared with ECMWF and National Centers for Environmental Prediction analyses to assess the skill of the model in simulating the evolution of synoptic systems. Trajectories of AWDs are tracked on time-longitude cross sections of 700 mbar vorticity, lower tropospheric divergence and precipitation rates. Cloud clusters on satellite imagery relate rather well to synoptic features on observational analyses as well as to spatial patterns of rain gage measurements but not consistently to simulated precipitation. Movement of major AWDs and the generation of new waves are handled realistically by the model. Model dynamics and physics appear to be more important than lateral boundary conditions in determining the course of simulations.