89th American Meteorological Society Annual Meeting

Sunday, 11 January 2009
Orographic Effects on the Evolution of African Easterly Wave-Mesoscale Convective Systems over Northern Africa
Phoenix Convention Center
Wilson Jones, North Carolina A&T State University, Greensboro, NC; and G. Tang, Y. L. Lin, and J. Spinks
Effects of mountains located in Northern Africa on the evolution of the African easterly wave-mesoscale convective system (AEW-MCS), which often serves as an originator for major hurricanes over eastern Atlantic, are analyzed by applying a mesoscale numerical model WRF-ARW. Specifically the pre-development period of Tropical Storm Debby (2006) that primarily formed over the Ethiopian Highlands (EH) region is studied in association with this AEW disturbance and the embedded MCS. Using infrared satellite imagery and numerically simulated results, numerous convective genesis and lysis periods are identified.

Our main objective is to test the hypothesis stated by previous studies, i.e. moisture and vertical velocity played a major role in the generation and maintenance of the convective cycles associated with the pre-tropical cyclone system as it traveled westward across Northern Africa. Originally, mountain effects generate vertical velocity and moisture, and as the system travels westward these parameters are controlled further by environmental factors. With the mountains in central and western North Africa replaced by flat terrains, we found that the mesoscale convective system is weakened and the convective cycles less evident. As the system moves west across Africa, adequate moisture fluxes are guided by the convective development, and the AEW is slightly adjusted by mountainous downstream from the EH region.

This work is supported by a grant from the National Oceanic and Atmospheric Administration (NOAA) Educational Partnership Program (EPP) under the cooperative agreement NA06OAR4810187.

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