Category: Uncategorized
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The collapse of circulation and the acceleration of upper air superrotation with shortwave optical depth
When the atmosphere is more opaque to longwaves than to shortwaves (panel a), the ground temperature is higher than the nearby atmosphere in radiative equilibrium. This jump in temperature causes strong meridional circulation near the surface, especially when the rotation effect is weak (e.g. the tropical regions). This circulation fills the entire troposphere with airs…
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Regime transition between eddy-driven and moist-driven circulation on High Obliquity Planets
The meridional overturning circulation has two regimes. Under weak insolation and fast rotation, the circulation is dominantly driven by momentum forcing (including friction, eddy momentum transport etc.), and is thermally-indirect in most of the low latitudes (mechanism). Under strong insolation and slow rotation, the circulation is dominantly driven by thermal forcing (including diabatic heating, eddy…
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Wetter Stratospheres on High Obliquity Planets
Given that high obliquity aquaplanets tend to be warmer than low obliquity equivalents, we investigate whether the ocean on the warmer high obliquity planets are more vulnerable to strong insolation. The stratospheric water vapor concentration (solid curves) is much higher under high obliquity especially when climate is warm. The stratospheric humidity seems to be better correlated…
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Mechanisms leading to a warmer climate on high obliquity planets
We first find the high obliquity planets to be warmer than their low obliquity equivalents, even when the climate is very warm (1800 W/m2 will blow up the low obliquity experiment), indicating the previously proposed ice-albedo feedback may not be the full story. Through a series of mechanism-denying experiments, we conclude that the relative warmness…
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Tropical and Extratropical General Circulation with a Meridional Reversed Temperature Gradient as Expected in a High Obliquity Planet
Will the general circulation be just reversed when reversing the meridional temperature gradient? The simple answer is NO. With a reversed meridional temperature gradient, circulation becomes thermally indirect, shallow, and weak. Explanation is as follows: Mid-latitude baroclinic eddies become bottom amplified, and this can be explained by the changes of the most unstable mode in the…
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MJO-like forcings at different longitudinal locations drive the SSWs to different fates: interaction with the mid-latitude jet zonal asymmetry
The zonal asymmetry of the MJO forcing itself also plays a role. In response to a circumglobal MJO-like forcing, or a longitudinal restricted one located at different locations, the SSWs can be either enhanced or suppressed [5]. Forced by circumglobal MJO-like forcing with increasing amplitude, the SSW first gets enhanced then suppressed as shown in the…