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Energetic constraints on the pattern of changes to the hydrological cycle under global warming

Bonan, David B. and Siler, Nicholas and Roe, Gerard H. and Armour, Kyle C. (2022) Energetic constraints on the pattern of changes to the hydrological cycle under global warming. . (Unpublished)

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The response of precipitation minus evaporation (P-E) to global warming is investigated using a moist energy balance model (MEBM) with a simple Hadley-Cell parameterization. The MEBM accurately emulates P-E changes simulated by a suite of global climate models (GCMs) under greenhouse-gas forcing. The MEBM also accounts for most of the intermodel differences in GCM P-E changes and better emulates GCM P-E changes when compared to the "wet-gets-wetter, dry-gets-drier" thermodynamic mechanism. The intermodel spread in P-E changes are attributed to intermodel differences in radiative feedbacks, which account for 60-70% of the intermodel variance, with smaller contributions from radiative forcing and ocean heat uptake. Isolating the intermodel spread of feedbacks to specific regions shows that tropical feedbacks are the primary source of intermodel spread in P-E changes. The ability of the MEBM to emulate GCM P-E changes is further investigated using idealized feedback patterns. A less negative and narrowly peaked feedback pattern near the equator results in more atmospheric heating, which strengthens the Hadley Cell circulation in the deep tropics through an enhanced poleward heat flux. This pattern also increases gross moist stability, which weakens the subtropical Hadley Cell circulation. These two processes in unison increase P-E in the deep tropics, decrease P-E in the subtropics, and narrow the Intertropical Convergence Zone. Additionally, a feedback pattern that produces polar-amplified warming reduces the poleward moisture flux by weakening the meridional temperature gradient and the Clausius-Clapeyron relation. It is shown that changes to the Hadley Cell circulation and the poleward moisture flux are crucial for understanding the pattern of GCM P-E changes under warming.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper ItemEarth System Grid Federation (ESGF) Portal ItemData
Bonan, David B.0000-0003-3867-6009
Roe, Gerard H.0000-0001-5906-4779
Armour, Kyle C.0000-0002-6833-5179
Additional Information:License: Attribution 4.0 International. The authors thank Polina Khapikova for helpful comments on an earlier draft of this paper. Part of this research was supported by the University of Washington Mary Gates Endowment for Undergraduate Students. D.B.B was supported by an American Meteorological Society (AMS) Graduate Fellowship and the National Science Foundation (NSF) Graduate Research Fellowship Program (NSF Grant DGE1745301). N.S. was supported by NSF Grant AGS-1954663. G.H.R. was supported by NSF Grants AGS-2019647 and P2C2-2102829. K.C.A. was supported by NSF Grants AGS-1752796 and AGS-2019647, and an Alfred P. Sloan Research Fellowship (Grant FG-2020-13568). We thank the climate modeling groups for producing and making available their model output, which is accessible at the Earth System Grid Federation (ESGF) Portal ( Data availability statement: The data for this study will be made available upon acceptance at
Funding AgencyGrant Number
University of WashingtonUNSPECIFIED
American Meteorological SocietyUNSPECIFIED
NSF Graduate Research FellowshipDGE-1745301
Alfred P. Sloan FoundationFG-2020-13568
Record Number:CaltechAUTHORS:20220606-736192000
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115037
Deposited By: George Porter
Deposited On:07 Jun 2022 14:14
Last Modified:25 Jul 2022 23:14

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