989 The Role of Orography in African Easterly Wave Genesis

Wednesday, 25 January 2017
Joshua Dylan White, North Carolina State University, Raleigh, NC; and A. R. Aiyyer

Handout (2.4 MB)

African easterly waves (AEWs) are synoptic-scale disturbances that modulate west African precipitation and are precursors of a majority of Atlantic hurricanes.  For decades, the proposed AEW genesis mechanism was the baroclinic-barotropic instability of the African Easterly Jet, but recent studies have shown that these instabilities alone cannot account for observed AEW growth rates. Recent studies have shown increasing support of triggering by mesoscale convection as an AEW genesis mechanism.  Furthermore, the geographical genesis location of AEWs coincide with the leeward region of significant orographic features, such as the Ethiopian Highlands or the Ahaggar Mountains, and during a season (July-October), these regions are highly convectively active.  Our goal is to determine the kinetic and thermodynamic effects of these orographic features on AEW dynamics.  In this study, we examine several seasons (1980-2015) using the Weather Research and Forecasting model (WRF) in order to modify the orography and compare model output to output from a control experiment as well as European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-Interim) and satellite derived products.  Using quantities from these data and a derived eddy kinetic energy budget, we diagnose AEW development across the experiments. Analysis of the effects of these orographic features on convection and AEWs will aid in determining the role of orography in AEW genesis.
- Indicates paper has been withdrawn from meeting
- Indicates an Award Winner