Large-Scale Drivers of Tropical Extreme Precipitation Events: The Example of French Overseas Territories
Cornillault, Erwan ; Peyrillé, Philippe ; Couvreux, Fleur ; Roehrig, Romain
Due to their severity and lack of predictability, understanding and forecasting extreme precipitation events (EPEs) is critical for disaster risk reduction. The present work documents the large-scale environment of tropical EPEs based on a 42-year data set combining dense rain-gauge networks that cover several tropical small islands and coastal regions. Approximately 10%-30% of EPEs are associated with a tropical storm or cyclone (TC), except for Reunion, for which its high topography makes it reach 55%. TCs multiply the EPE probability by a factor of 4-15, especially during TCs of category 1 or higher. A composite analysis demonstrates that the remaining large part of EPEs occurs within large-scale and strong moist, convective, and cyclonic wind anomalies resulting from the superimposition of intraseasonal, seasonal-to-annual, and interannual timescales. These intense anomalies come essentially from intraseasonal variability, and lower frequencies improve the effect of intraseasonal events in creating a favorable environment for EPEs.</p>
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