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Dynamics and Energy Balance of the Hadley Circulation and the Tropical Precipitation Zones. Part II: Sensitivity to Meridional SST Distribution

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  • 1 National Institute for Enviromental Studies, Tsukuba, Ibaraki, Japan
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Abstract

A series of GCM experiments is performed in order to examine the dynamics of the time-averaged distribution of precipitation and Hadley circulation in low-latitude areas. As an extension to Part I of this study, the sensitivity to the latitudinal distribution of the globally prescribed sea surface temperature (SST) is examined. When the peak of SST is not at the equator but nearby, a single precipitation peak appears on the opposite side of the equator. When the latitude of the SST peak becomes high enough (about 15°), an abrupt jump of the precipitation peak is observed. This behavior is completely different if the evaporation from the ocean is estimated independent of the surface wind speed.

Factors controlling the latitude of the precipitation zone are discussed. It is found that one essential component is the convergent flow in the planetary boundary layer, which is driven by the SST gradient. Another important factor is the net moist static energy input into the atmosphere, which is the difference between the energy input from the surface and the radiative loss. The near-neutral stratification of the atmosphere, which may be partially determined by the distribution of the SST, is also considered to be important because it controls the moist static energy balance of the atmosphere.

Abstract

A series of GCM experiments is performed in order to examine the dynamics of the time-averaged distribution of precipitation and Hadley circulation in low-latitude areas. As an extension to Part I of this study, the sensitivity to the latitudinal distribution of the globally prescribed sea surface temperature (SST) is examined. When the peak of SST is not at the equator but nearby, a single precipitation peak appears on the opposite side of the equator. When the latitude of the SST peak becomes high enough (about 15°), an abrupt jump of the precipitation peak is observed. This behavior is completely different if the evaporation from the ocean is estimated independent of the surface wind speed.

Factors controlling the latitude of the precipitation zone are discussed. It is found that one essential component is the convergent flow in the planetary boundary layer, which is driven by the SST gradient. Another important factor is the net moist static energy input into the atmosphere, which is the difference between the energy input from the surface and the radiative loss. The near-neutral stratification of the atmosphere, which may be partially determined by the distribution of the SST, is also considered to be important because it controls the moist static energy balance of the atmosphere.

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