PCIC science brief: Projected changes to short-duration extreme rainfall
Date
2015-12
Authors
Pacific Climate Impacts Consortium (PCIC)
Journal Title
Journal ISSN
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Publisher
Pacific Climate Impacts Consortium (PCIC)
Abstract
Publishing in the Reviews of Geophysics, Westra et al (2014) summarize the current state of research in the analysis of future changes to the intensity, frequency and duration of extreme rainfall. Their literature review highlights the complicated relationship between short duration extreme rainfall and atmospheric temperature. In some locations, such extreme precipitation does not simply scale with the ability of the atmosphere to hold moisture (i.e. at the Clausius-Clapyron rate of 6 to 7% per C). Instead, at these locations the general pattern is that such a relationship is found to hold up to about 12 C, but between 12 and 24 C extreme precipitation appears to increase more strongly with warming. This is partly due to an increase in convective rainfall. However, above about 24 C, the pattern at these locations is one in which the response of precipitation to increasing temperature appears to be weaker, eventually reversing. This may be due to decreased moisture availability at these temperatures, though Westra et al. note that "the mechanism that causes these moisture deficits remains to be investigated." The authors also find that anticipated changes in sub-daily precipitation associated with a warming climate will "significantly affect the magnitude and frequency of urban and rural flash floods.
Compared to daily rainfall, Westra et al. find that sub-daily and sub-hourly rainfall are more sensitive to local surface temperatures. They also report that while sub-daily precipitation observations are too scarce to determine regional trends, geographic location will likely affect rates of change in daily precipitation extremes. In terms of making projections of future changes in these events, the authors find that, owing to the resolution of current global climate models, they are limited in their ability to simulate such precipitation events. In particular, the models are generally not run at sufficient resolution to accurately resolve the necessary convective processes, though some very high-resolution “convection permitting” regional climate models operate at a sufficient resolution to potentially be useful in projecting such extremes. One implication of these findings is that we cannot currently make credible projections of sub-daily rainfall events.
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Keywords
UN SDG 13: Climate Action, #science brief, #PCIC publication