29th Conference on Hurricanes and Tropical Meteorology


The Influence of the Madden Julian Oscillation over Tropical North Africa

Michael J. Ventrice, SUNY, Albany, NY; and C. Thorncroft and P. Roundy

The role of the Madden Julian Oscillation (MJO) on tropical north African rainfall is explored. Previous work has suggested that over Africa, the MJO can modulate the surface monsoon flow and moisture supply, and hence rainfall. In addition it can also modulate the cyclonic shear on the equatorward flank of the African easterly jet, which can, in turn, affect African easterly wave (AEW) activity. Using the Wheeler and Hendon's Real-time Multivariable MJO Indices (RMM), each phase of the MJO will be examined to see how West African rainfall variability is modulated. This will include how downstream tropical cyclogenesis in the tropical Atlantic is affected. We will show that the MJO enhances convection along the inter-tropical convergence zone (ITCZ) over Africa during phases 8,1, 2, and,3, and suppresses convection over the sub-Saharan zone during phases 4-7. An eddy kinetic energy (EKE) analysis was performed to make composites of moderate-strong MJO events to highlight AEW activity. During phases 1-3, positive EKE anomalies dominate much of tropical Africa, presumably acting to enhance AEWs for a period of time. Negative EKE anomalies dominate Africa during phases 6-8. Stronger (Weaker) AEWs lead to more (less) downstream tropical cyclogenesis. During 1974-2008, we find the highest total amount of tropical cyclogenesis events over the tropical Atlantic Ocean occur during phases 1-3, with a peak in phase 2. The basic state over Africa is modulated by an approaching and passing MJO event and will be highlighted here.

Poster Session 1, Posters: TCs and Climate, Monsoons, HFIP, TC Formation, Extratropical Transition, Industry Applications, TC Intensity, African Climate and Weather
Tuesday, 11 May 2010, 3:30 PM-5:15 PM, Arizona Ballroom 7

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