Understanding the Dynamics of Future Changes in Extreme Precipitation Intensity

Abstract

Climate model projections of extreme precipitation intensity depend heavily on the region: some regions will experience exceptionally strong increases in extreme precipitation intensity, while other regions will experience decreases in extreme precipitation intensity. These regional variations are closely related to regional changes in large-scale ascent during extreme precipitation events—that is, “extreme ascent”—but the drivers of extreme ascent changes remain poorly understood. Using output from a large ensemble of the Canadian Earth System Model version 2, we show that subtropical changes in extreme ascent likely result from changes in the horizontal scale of ascending anomalies, which are in turn associated with changes in vertical stability. Near the equator, changes in the seasonal mean circulation may be an important factor influencing extreme ascent, but this finding is model dependent.