Climatology Study of African Easterly Wave and Mesoscale Convective System in Northern Africa

In this study, the climatology of African Easterly Waves (AEWs) and their associated mesoscale convective systems (MCSs) that developed over Northern Africa from 1996 to 2006 are investigated. Based on Meteosat infrared (IR) satellite imagery and Global Forecast System (GFS-ANL) analysis data, we identified several convective genesis and lysis periods. Based on the analysis of pre-tropical cyclones of that 10 year period, we found some interesting attributes which played major roles in the maintenance of the mesoscale convective system as it traveled westward across Northern Africa. Initially, the diurnally induced mesoscale convection over the mountains was organized into a MCS by the AEW. This coupled AEW-MCS system is then maintained by orographically induced upward motion and moisture convergence to provide the upward moisture flux needed for maintaining the MCS when it travels across the African continent. This mechanism and the large-scale features of the AEWs and moisture distribution are examined by analyzing the GFS reanalysis data, while the mesoscale processes associated with the mechanism are examined by running the Weather Research and Forecasting model Version 3.0. Several sensitivity simulations are performed to isolate some physical and dynamical processes. NCEP Reanalysis for the 1996-2006 span was used to analyze the AEW features.