12A.2 Variability of the Spatial Instability of the African Easterly Jet

Thursday, 10 January 2019: 9:00 AM
North 121BC (Phoenix Convention Center - West and North Buildings)
Joshua Dylan White, North Carolina State Univ., Raleigh, NC; and A. R. Aiyyer

African easterly waves (AEWs) are synoptic scale disturbances known often to develop into North Atlantic tropical cyclones and to impact convective systems over northern Africa during the northern hemisphere summer. During these summer months, the African easterly jet (AEJ) has been shown to exhibit a potential vorticity gradient reversal, permitting AEW development through mixed barotropic-baroclinic instabilities. Due to the localized structure of the AEJ, the spatial instability of the jet can impact the growth of AEWs. Furthermore, given the intraseasonal variation of the AEJ, we must further consider the temporal variability of this spatial instability. In this study, we examine how this temporal variability affects AEW development and if it can help explain the intermittence of AEW activity. To do so, we use the same hydrodynamic model used recently to study AEWs as convectively triggered perturbations, and in this model, we maintain a fixed global circulation and allow the model to run for several weeks in order to determine spatial instability characteristics of the AEJ. This process is repeated for various basic states from reanalysis data across different periods of the northern summertime in order investigate the intraseasonal variability of these characteristics.
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