Characterizing the Hadley circulation response through regional climate feedbacks
The robust weakening of the tropical atmospheric circulation in projections of anthropogenic warming is associated with substantial changes in regional and global climate. The present study focuses on understanding the response of the annual-mean Hadley circulation from a perspective of interactions between climate feedbacks and tropical circulation. Simulations from an ensemble of coupled ocean–atmosphere models are used to quantify changes in Hadley cell strength in terms of feedbacks, radiative forcing, ocean heat uptake, atmospheric eddies, and gross moist stability. Climate feedbacks are calculated for the model integrations from phase 5 of CMIP (CMIP5) using radiative kernels. Tropical mean circulation is found to be reduced by up to 2.6% K^(−1) for an abrupt quadrupling of carbon dioxide concentration. The weakening is characterized by an increase in gross moist stability, by an increase in eddy heat flux, and by positive extratropical feedbacks, such as those associated with lapse rate and sea ice response. Understanding the impact of radiative feedbacks on the large-scale circulation provides a framework for constraining uncertainty in the dynamic climate response, including the hydrological cycle.
Additional Information© 2016 American Meteorological Society. Manuscript received 17 June 2015, in final form 9 October 2015. We thank three anonymous reviewers for their helpful comments on the manuscript. This work also benefited from discussions with Tim Merlis, Gerard Roe, and Yen-Ting Hwang. The authors were supported by the Caltech Engineering and Applied Science Discovery Fund, the Foster and Coco Stanback Postdoctoral Fellowship, and the National Science Foundation (AGS-1524569 and AGS-1462544).
Published - jcli-d-15-0424.1.pdf