Earlier Seasonal Onset of Intense Mesoscale Convective Systems in the Congo Basin Since 1999

Taylor, Christopher M. ; Fink, Andreas H. ; Klein, Cornelia ; Parker, Douglas J. ; Guichard, Françoise ; Harris, Philip P. ; Knapp, Kenneth R.

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Mesoscale convective systems (MCSs) produce some of the most intense rainfall on the planet, and their response to climate variability and change is rather uncertain. Under global warming, increased water vapor is expected to intensify the most extreme rain events and enhance flood frequency. However, MCS dynamics are also sensitive to other atmospheric variables, most notably, wind shear. Here we build on a recent study showing strong MCS intensification in the African Sahel, and examine evidence of similar trends elsewhere in tropical Africa. Using satellite data, we find a remarkable increase post-1999 in intense MCS frequency over the Congo Basin during the month of February. This earlier onset of the spring rainy season has been accompanied by strong increases in the February meridional temperature gradient and associated wind shear. This supports the hypothesis that contrasts in warming across the continent can drive important decadal-scale trends in storm intensity.
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