Dynamic Amplification of Subtropical Extreme Precipitation in a Warming Climate

Jesse Norris, Gang Chen and Chao Li

Abstract

Projected precipitation changes in a warming climate vary considerably, spatially, and between intensities. The changes can be greater or less than the ∼7% K−1 Clausius‐Clapeyron (CC) prediction, owing to dynamic effects. Using two global‐climate‐model large ensembles, we quantify the dynamically induced changes to precipitation extremes from the present (1996–2005) to late‐21st‐century (2071–2080) climates, as a function of recurrence interval, focusing on the subtropics. We separate non‐CC changes into a term proportional to the present‐day vertical‐velocity spatial pattern (i.e., an amplification or damping thereof by a constant factor) and a residual. The amplitude term varies with recurrence interval, approximately canceling (doubling) CC for moderate (large) extremes, increasing precipitation variability. Contrastingly, the residual is quasi‐uniform across recurrence intervals but spatially heterogeneous, weakening extremes over dry zones. This residual may be related to Hadley cell expansion, although this explanation is insufficient to explain many features, and other possible mechanisms are discussed.

Gang Chen

Professor, Dept. of Atmospheric and Oceanic Sciences, University of California, Los Angeles

Math Sci Building 7149, Los Angeles, CA 90095

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Dynamic Amplification of Subtropical Extreme Precipitation in a Warming Climate

Published in Geophysical Research Letters, 2020

Recommended citation: Jesse Norris, Gang Chen and Chao Li, 2020: Dynamic Amplification of Subtropical Extreme Precipitation in a Warming Climate, Geophysical Research Letters, 47, 1–15, doi:10.1029/2020GL087200.

Abstract

Projected precipitation changes in a warming climate vary considerably, spatially, and between intensities. The changes can be greater or less than the ∼7% K−1 Clausius‐Clapeyron (CC) prediction, owing to dynamic effects. Using two global‐climate‐model large ensembles, we quantify the dynamically induced changes to precipitation extremes from the present (1996–2005) to late‐21st‐century (2071–2080) climates, as a function of recurrence interval, focusing on the subtropics. We separate non‐CC changes into a term proportional to the present‐day vertical‐velocity spatial pattern (i.e., an amplification or damping thereof by a constant factor) and a residual. The amplitude term varies with recurrence interval, approximately canceling (doubling) CC for moderate (large) extremes, increasing precipitation variability. Contrastingly, the residual is quasi‐uniform across recurrence intervals but spatially heterogeneous, weakening extremes over dry zones. This residual may be related to Hadley cell expansion, although this explanation is insufficient to explain many features, and other possible mechanisms are discussed.

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