The Atmospheric Energy Constraint on Global-Mean Precipitation Change
The Atmospheric Energy Constraint on Global-Mean Precipitation Change
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DOI：
10.1175/jcli-d-13-00163.1
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发表时间：
2014-01-01
影响因子：
4.9
通讯作者：
Hartmann, Dennis L.
中科院分区：
文献类型：
--
作者：
Pendergrass, Angeline G.;Hartmann, Dennis L.
耦合模式相互比较项目（CMIP 5）第5阶段的模型有力地预测，全球平均降水量随全球平均表面温度增加的增加率远低于水蒸气的增加率。本文的目的是详细解释辐射冷却对降水增加的制约机制。在全球变暖模拟中，由温度和湿度变化引起的晴空大气辐射冷却的变化与GCM预测的多模式全球平均降水增加非常一致（类似于1.1 W m（-2）K-1）。在固定比湿度的大气中，来自大气顶部的辐射冷却（TOA）响应于表面和大气的均匀温度增加而增加，而与地面交换的大气冷却作用则减少了，因为地面向上发射的长波辐射比大气向下发射的长波辐射增加得多。当一个固定的相对湿度（RH）的假设，但是，均匀变暖导致一个小得多的增加冷却在TOA，和表面的贡献逆转增加净冷却率由于增加向下排放的水蒸气。当相对湿度固定时，降水变化对直减率变化的敏感性是适度的。二氧化碳减少TOA排放，对地表通量的影响很小，从而抑制降水。净大气冷却响应，从而降水响应CO2引起的变暖在固定的RH主要是由地面通量的变化。云的作用进行了讨论。模式间传播的降水增加率在整个CMIP 5模拟归因于大气冷却的差异。
Models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) robustly predict that the rate of increase in global-mean precipitation with global-mean surface temperature increase is much less than the rate of increase of water vapor. The goal of this paper is to explain in detail the mechanisms by which precipitation increase is constrained by radiative cooling. Changes in clear-sky atmospheric radiative cooling resulting from changes in temperature and humidity in global warming simulations are in good agreement with the multimodel, global-mean precipitation increase projected by GCMs (similar to 1.1 W m(-2) K-1).In an atmosphere with fixed specific humidity, radiative cooling from the top of the atmosphere (TOA) increases in response to a uniform temperature increase of the surface and atmosphere, while atmospheric cooling by exchange with the surface decreases because the upward emission of longwave radiation from the surface increases more than the downward longwave radiation from the atmosphere. When a fixed relative humidity (RH) assumption is made, however, uniform warming causes a much smaller increase of cooling at the TOA, and the surface contribution reverses to an increase in net cooling rate due to increased downward emission from water vapor. Sensitivity of precipitation changes to lapse rate changes is modest when RH is fixed. Carbon dioxide reduces TOA emission with only weak effects on surface fluxes, and thus suppresses precipitation. The net atmospheric cooling response and thereby the precipitation response to CO2-induced warming at fixed RH are mostly contributed by changes in surface fluxes. The role of clouds is discussed.Intermodel spread in the rate of precipitation increase across the CMIP5 simulations is attributed to differences in the atmospheric cooling.