让我们暂时考虑对流层堆叠层组成。砧云只能发现对流层上层的,因为这就是他们必须扩展水平由于对流层顶作为天然屏障(见图1。在哈特曼,拉尔森下面的链接)。假设水分不穿透的对流层和平流层层含有水分充分吸收长波辐射(显然这不是真的,但它帮助这里的点)。这意味着即将离任的长波辐射从这个上层不能吸收水蒸气的层上面。自包含砧的层云将吸收所有即将离任的长波辐射下面的层(通过我们的假设上述),我们可以得出结论,这一层是最重要的一层,用来决定多少辐射空间,因此,* *冷却* *大气层。这解释了一个大气层有助于冷却但并不能解释为什么冷却降低与减少水汽混合比。答案可以解释的大气温度垂直梯度。大气中的干绝热递减率\ Gamma_d美元= 10 $ K /公里。潮湿的绝热递减率\ Gamma_w美元= 6 $ K /公里。 The more the water vapor mixing ratio decreases, the closer the lapse rate will be to $\Gamma_d$. And thus the upper most layer of the troposphere will be colder compared to a situation where the water vapor mixing ratio is high. A colder top layer will radiate less and therefore cooling decreases, since there is less outgoing long wave radiation. The FAT assumes that the temperature of this upper atmospheric layer is independent of surface temperature and thus, would amplify warming. What changes is the height of the upper layer - the troposphere has a larger vertical extent in a warming climate. [Hartmann, Larson - An important constraint on tropical cloud - climate feedback][1] [1]: https://doi.org/10.1029/2002GL015835
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