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Hemispheric Asymmetry of Tropical Expansion Under CO 2 Forcing
Author(s) -
WattMeyer O.,
Frierson D. M. W.,
Fu Q.
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl083695
Subject(s) - hadley cell , climatology , southern hemisphere , northern hemisphere , atmospheric sciences , environmental science , radiative forcing , forcing (mathematics) , ozone depletion , climate model , climate change , stratosphere , geology , general circulation model , oceanography
The degree of Hadley cell expansion under global warming will have a substantial impact on changing rainfall patterns. Most previous studies have quantified changes in total tropical width, focused on the Southern Hemisphere Hadley cell or considered each hemisphere's response to a multitude of anthropogenic forcings. It is shown here that under exclusive CO 2 forcing, climate models predict twice as much Hadley cell expansion in the Southern Hemisphere relative to the Northern Hemisphere. This asymmetry is present in the annual mean expansion and all seasons except boreal autumn. It is robust across models and Hadley cell edge definitions. It is surprising since asymmetries in simulated Hadley cell expansion are typically attributed to stratospheric ozone depletion or aerosol emission. Its primary cause is smaller sensitivity of the Northern Hemisphere Hadley cell to static stability changes. The pattern of sea surface warming and the CO 2 direct radiative effect also contribute to the asymmetry.