Effects of Seasonal Solar Forcing on Latitudinal Asymmetry of the ITCZ

Shang-Ping Xie Graduate School of Environmental Earth Science, Hokkaido University, Sapporo, Japan

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Abstract

A coupled ocean-atmosphere model is used to investigate the effects of seasonal variation in solar radiation on the configuration of the intertropical convergence zone. The model maintains a Northern Hemispheric ITCZ under annual mean insolation, with convection being suppressed in the Southern Hemisphere. In the presence of seasonal variations, a Southern Hemispheric ITCZ develops in boreal winter and spring in response to the seasonal rise in local solar radiation. As a result, the equatorial asymmetry of the annual-mean model climatology is reduced. The latitudinal asymmetry of the model climate is thus determined by a balance between the symmetry-breaking land forcing and the symmetry-restoring seasonal solar forcing.

Abstract

A coupled ocean-atmosphere model is used to investigate the effects of seasonal variation in solar radiation on the configuration of the intertropical convergence zone. The model maintains a Northern Hemispheric ITCZ under annual mean insolation, with convection being suppressed in the Southern Hemisphere. In the presence of seasonal variations, a Southern Hemispheric ITCZ develops in boreal winter and spring in response to the seasonal rise in local solar radiation. As a result, the equatorial asymmetry of the annual-mean model climatology is reduced. The latitudinal asymmetry of the model climate is thus determined by a balance between the symmetry-breaking land forcing and the symmetry-restoring seasonal solar forcing.

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