Abrupt circulation responses to tropical upper-tropospheric warming in a relatively simple stratosphere-resolving AGCM

Shuguang Wang, Edwin Gerber, Lorenzo M. Polvani

Research output: Contribution to journalArticle

Abstract

The circulation response of the atmosphere to climate change-like thermal forcing is explored with a relatively simple, stratosphere-resolving general circulation model. The model is forced with highly idealized physics, but integrates the primitive equations at resolution comparable to comprehensive climate models. An imposed forcing mimics the warming induced by greenhouse gasses in the low-latitude upper troposphere. The forcing amplitude is progressively increased over a range comparable in magnitude to the warming projected by Intergovernmental Panel on Climate Change coupled climate model scenarios. For weak to moderate warming, the circulation response is remarkably similar to that found in comprehensive models: the Hadley cell widens and weakens, the tropospheric midlatitude jets shift poleward, and the Brewer-Dobson circulation (BDC) increases. However, when the warming of the tropical upper troposphere exceeds a critical threshold,;5K, an abrupt change of the atmospheric circulation is observed. In the troposphere the extratropical eddy-driven jet jumps poleward nearly 108. In the stratosphere the polar vortex intensifies and the BDC weakens as the intraseasonal coupling between the troposphere and the stratosphere shuts down. The key result of this study is that an abrupt climate transition can be effected by changes in atmospheric dynamics alone, without need for the strong nonlinearities typically associated with physical parameterizations. It is verified that the abrupt climate shift reported here is not an artifact of the model's resolution or numerics.

Original languageEnglish (US)
Pages (from-to)4097-4115
Number of pages19
JournalJournal of Climate
Volume25
Issue number12
DOIs
StatePublished - Jun 2012

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atmospheric general circulation model
stratosphere
troposphere
warming
climate modeling
Hadley cell
atmospheric dynamics
polar vortex
Intergovernmental Panel on Climate Change
climate
atmospheric circulation
nonlinearity
artifact
general circulation model
parameterization
eddy
physics
climate change
atmosphere

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

Abrupt circulation responses to tropical upper-tropospheric warming in a relatively simple stratosphere-resolving AGCM. / Wang, Shuguang; Gerber, Edwin; Polvani, Lorenzo M.

In: Journal of Climate, Vol. 25, No. 12, 06.2012, p. 4097-4115.

Research output: Contribution to journalArticle

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