Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 183-701, Pasadena, California 91109-8099, USA.
Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, Los Angeles, California 90095, USA.
Nat Commun. 2017 Jun 7;8:15771. doi: 10.1038/ncomms15771.
The change of global-mean precipitation under global warming and interannual variability is predominantly controlled by the change of atmospheric longwave radiative cooling. Here we show that tightening of the ascending branch of the Hadley Circulation coupled with a decrease in tropical high cloud fraction is key in modulating precipitation response to surface warming. The magnitude of high cloud shrinkage is a primary contributor to the intermodel spread in the changes of tropical-mean outgoing longwave radiation (OLR) and global-mean precipitation per unit surface warming (dP/dT) for both interannual variability and global warming. Compared to observations, most Coupled Model Inter-comparison Project Phase 5 models underestimate the rates of interannual tropical-mean dOLR/dT and global-mean dP/dT, consistent with the muted tropical high cloud shrinkage. We find that the five models that agree with the observation-based interannual dP/dT all predict dP/dT under global warming higher than the ensemble mean dP/dT from the ∼20 models analysed in this study.
在全球变暖及年际变化下，全球平均降水量的变化主要由大气长波辐射冷却的变化所控制。在这里我们表明，哈德利环流上升支的加强以及热带高空云量的减少是调节降水对地表增暖响应的关键。高空云量减少的幅度是造成热带平均向外长波辐射（OLR）和全球平均每单位地表增暖降水量（dP/dT）变化在年际变化和全球变暖两种情况下，模式间差异的主要因素。与观测结果相比，大多数耦合模式比较计划第五阶段模型低估了年际热带平均 dOLR/dT 和全球平均 dP/dT 的变化率，这与热带高空云量减少有关。我们发现，与基于观测的年际 dP/dT 一致的五个模型预测的全球变暖下的 dP/dT 均高于本研究分析的约 20 个模型的集合平均 dP/dT。
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