408 The Potential Vorticity Dynamics of African Easterly Waves

Tuesday, 24 January 2017
4E (Washington State Convention Center )
James O. H. Russell, North Carolina State Univ., Raleigh, NC; and A. R. Aiyyer

Handout (2.7 MB)

African easterly waves (AEWs) are synoptic-scale disturbances associated with the African Easterly Jet (AEJ) that move westward across sub-Saharan Africa during the West African Monsoon season. It has been shown that the barotropic and baroclinic extraction of energy from the AEJ is not sufficient to sustain AEWs, and that moist convection may have an important role in their maintenance. To investigate how convection (and diabatic heating) affect the structure and evolution of AEWs, this study examines a potential vorticity (PV) budget. Furthermore, through the PV budget, this study aims to test the hypothesis that convection and AEWs may interact through the Diabatic Rossby Wave (DRW) mechanism. To do this, a variety of AEW case studies are simulated using the Weather Research and Forecasting model, with sensitivity tests that either eliminate convection or it’s effects (diabatic heating and momentum adjustment). Early results suggest that without convection, the PV structure of the AEW is limited to the upper-levels and the low-level structure of AEWs, important for Hurricane genesis, is weak or not present. This study works as a part of a larger study on AEWs, their PV structure and growth, and the role of convection in their evolution.
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