Patterns of tropical weather have a significant influence on Earth’s climate, but how they may change with a warming climate is not fully understood. Over sixty-percent of rainfall in tropical regions is attributed to clusters of thunderstorms with sizes generally ranging from 50 miles to several hundred miles which persist for several hours or more. While it is clear that these convective systems are of great importance to the tropical hydrological cycle, research has not yet shown how much they contribute to the intensity of rain events. Further, prior research hypothesizes that these storm clusters may occur more frequently in the future, but they are still not well represented in projections of tropical climate with warming. A new study, partially funded by CPO’s Climate Variability & Predictability (CVP) and Modeling, Analysis, Predictions and Projections (MAPP) Programs, uses rainfall and convection observational data and numerical models to investigate how much storm clusters affect the rate of precipitation compared to storms that are not clustered. Researchers from the University of Washington, including CVP- and MAPP- supported scientist Daehyun Kim, find that rainfall increases in these storms until the air moisture reaches a level too high that convection can no longer occur. Crossing this moisture threshold (about seventy-percent) changes the rainfall rate in the system. These results, published in Science Advances, demonstrate the necessity of correctly representing these storm clusters in models of extreme weather in the tropics. This study contributes to a growing body of work supporting the CVP initiative to advance the understanding of rainfall extremes in the tropics and their predictability. It also serves to support a MAPP initiative to address key issues in the representation of extreme events in Earth system models.
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