Title: The impact of equilibrating hemispheric albedos on tropical performance in the HadGEM2-ES coupled climate model

Abstract

Despite the fact that the southern hemisphere contains a far greater proportion of dark ocean than the northern hemisphere, the total amount of sunlight reflected from the hemispheres is equal. However, the majority of climate models do not adequately represent this equivalence. Here we examine the impact of equilibrating hemispheric albedos by various idealised methods in a comprehensive coupled climate model and find significant improvements in what have been considered longstanding and apparently intractable model biases. Monsoon precipitation biases almost vanish over all continental land areas, the penetration of monsoon rainfall across the Sahel and the west African monsoon “jump” become well represented, and indicators of hurricane frequency are significantly improved. The results appear not to be model specific, implying that hemispheric albedo equivalence may provide a fundamental constraint for climate models that must be satisfied if the dynamics driving these processes, in particular the strength of the Hadley cell, are to be adequately represented. Cross-equatorial energy transport is implicated as a crucial component that must be accurately modelled in coupled general circulation models. The results also suggest that the commonly used practice of prescribing sea-surface temperatures in models provides a less accurate represention of precipitation than constraining the hemisphericmore » albedos.« less

Authors:

Haywood, Jim M. ^[1]; Jones, Andy ^[2]; Dunstone, Nick ^[2]; Milton, Sean ^[2]; Vellinga, Michael ^[2]; Bodas-Salcedo, Alejandro ^[2]; Hawcroft, Matt ^[3]; Kravitz, Ben ^[4]; Cole, Jason ^[5]; Watanabe, Shingo ^[6]; Stephens, Graeme ^[7]

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+ Show Author Affiliations

1. Met Office Hadley Centre, Exeter (United Kingdom); Univ. of Exeter, Exeter (United Kingdom)
2. Met Office Hadley Centre, Exeter (United Kingdom)
3. Univ. of Exeter, Exeter (United Kingdom)
4. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
5. Canadian Centre for Climate Modeling and Analysis, Environment Canada, Toronto, ON (Canada)
6. Japan Agency for Marine-Earth Science and Technology, Yokohama (Japan)
7. JPL, Pasadena, CA (United States)

Publication Date:

Thu Jan 14 00:00:00 EST 2016

Research Org.:

Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1251308

Report Number(s):

PNNL-SA-108138
Journal ID: ISSN 0094-8276; 600305000

Grant/Contract Number:  

AC05-76RL01830

Resource Type:

Accepted Manuscript

Journal Name:

Geophysical Research Letters

Additional Journal Information:

Journal Volume: 43; Journal Issue: 1; Journal ID: ISSN 0094-8276

Publisher:

American Geophysical Union

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; climate models; inter-hemispheric; albedo symmetry