科研之友
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摘要
The projected changes in temperature due to global warming will have a profound effect on the behaviour of midlatitude eddies. Using an idealized moist global circulation model, the atmospheric barotropic energy balance is studied over a wide range of climates. The barotropic energy cycle is found to shift poleward as the long-wave optical thickness increases in concert with the poleward shift of the static stability, driven by the poleward shift of the upper-level baroclinicity. The baroclinic-barotropic conversion (barotropization) shows a non-monotonic behaviour at midlatitudes as the climate becomes warmer, and reaches a maximum value around present-day climate with lower values for colder and warmer climates. This is found to be associated with the non-monotonic behaviour of the stratification. Similar to the barotropization, the strength of the inverse energy cascade also shows a non-monotonic behaviour as the climate becomes warmer. However, the inverse energy cascade does not shift poleward, but rather corresponds to the uniform latitudinal distribution of the quasi-geostrophic supercriticality through all climates. The eddy-mean flow interactions increase and transfer kinetic energy from the eddies to the mean flow at low and high latitudes, and from the mean flow to the eddies at midlatitudes, as the climate becomes warmer. This occurs mostly due to the decrease of the latitudinal extent of the mean flow at high latitudes, which increases and shifts equatorward the meridional shear of the barotropic mean zonal wind. The findings of this study imply that under global warming the eddy flow is dominated by eddy-mean flow interactions and has a more baroclinic nature.
- 出版日期2017-7
