Climate Systems Interaction Group

Tightening of tropical ascent and high clouds key to precipitation change in a warmer climate.

Hui Su, Jonathan H. Jiang, J. David Neelin, T. Janice Shen, Chengxing Zhai, Qing Yue, Zhien Wang, Lei Huang, Yong-Sang, Graeme L. Stephens, and Yuk L. Yung
Nature Communications, 8 15771 1-9, doi:10.1038/ncomms15771.
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Abstract 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/dTs) 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/dTs and global-mean dP/dTs, consistent with the muted tropical high cloud shrinkage. We find that the five models that agree with the observation-based interannual dP/dTs all predict dP/dTs under global warming higher than the ensemble mean dP/dTs from the ~20 models analysed in this study.

Citation Su, H. et al. 2017, Tightening of tropical ascent and high clouds key to precipitation change in a warmer climate. Nature Communications, 8 15771, doi:10.1038/ncomms15771.

Acknowledgments. We acknowledge the funding support from NASA NEWS, AST, MAP, NDOA and NSF. We greatly appreciate Michael Wong in making the schematic figure. We thank Shang- min Long, Ryan Stanfield and Jung-Min Park for assistance in some parts of the aux- icillary analyses. We thank Drs Brian Soden and Karen Shell for providing the radiative kernel functions. We appreciate helpful discussions with Drs Chris Bretherton, Anthony DeAngelis, Feifei Jin, Xin Qu and Shang-Ping Xie. We thank three anonymous reviewers for insightful suggestions. This work was performed at Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.