Recent work has indicated that atmospheric radiative heating reduces the kinetic energy of large-scale eddies in the midlatitudes. However, a physical mechanism that connects radiation to the midlatitude eddy kinetic energy is still uncertain. Using a high-resolution general circulation model we perform an experiment in which the radiative cooling profile at each model time step is overwritten with the climatological mean, computed from a control simulation. This approach separates the mean and transient effects of radiative heating on the extratropical circulation. We find that, when radiative heating is fixed, the globally-averaged eddy kinetic energy is enhanced by ∼6%. We show that thermal radiation dampens temperature anomalies near the surface and tropopause in low-pressure systems, destroying eddy available potential energy and eddy kinetic energy. We identify this as a possible mechanism by which atmospheric radiative heating weakens midlatitude cyclones.

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为什么大气辐射加热会削弱中纬度气旋？


最近的研究表明，大气辐射加热降低了中纬度地区大规模涡流的动能。然而，将辐射与中纬度涡流动能联系起来的物理机制仍不确定。我们使用高分辨率大气环流模型进行了一项实验，其中每个模型时间步长的辐射冷却剖面都被根据控制模拟计算出的气候平均值覆盖。这种方法将辐射加热对温带环流的平均影响和瞬态影响分开。我们发现，当辐射加热固定时，全局平均涡动能增强约 6%。我们表明，热辐射抑制了低压系统中地表和对流层顶附近的温度异常，破坏了涡流的可用势能和涡流动能。我们认为这是大气辐射加热削弱中纬度气旋的可能机制。