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Summer and winter precipitation in East Asia scale with global warming at different rates

Summer and winter precipitation in East Asia scale with global warming at different rates

Abstract
Future changes of regional precipitation are of great scientific and societal interests. Large uncertainties still exist in their projections by models. Mechanistic understanding is therefore necessary. Here we demonstrate robust features of the percentage change of precipitation normalized to surface temperature change (%/K) under global warming, referred to as scaling of precipitation with temperature in East Asia. We find that land precipitation in the summer scales at ~3%/K, well below the scaling rate of the Clausius-Clapeyron relationship for atmospheric water vapor content, but the scaling in winter is comparable to the Clausius-Clapeyron scaling at ~7%/K. By using moisture budget analysis of model simulations, we show that this scaling and the seasonal contrast can be clearly attributed to the robust climate changes of steeping moisture gradient, weakening westerly jets, and increasing hydrological amplitude of atmospheric eddies.

Introduction
Anthropogenic greenhouse emissions have caused global warming that is expected to continue in the 21st Century1,2,3. Associated with the warming are changes of precipitation that affect critical water resources for many sectors in the society2,4,5,6,7. For the Earth as a whole, the scaling of precipitation with temperature is constrained by the rate of atmospheric radiative cooling at about 2–3%/K8,9. On regional scales, however, model projections of future changes in precipitation display large inter-model differences with much larger spatial variations than the warming. Regional dynamics has been shown to play an important role in these variations10, but details of specific processes causing regional precipitation changes are still not well understood. Confidence is therefore low in these projections2,3. More insights into the physical mechanisms are needed
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