The hydrological cycle over a wide range of climates simulated with an idealized GCM
The hydrological cycle over a wide range of climates simulated with an idealized GCM
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DOI：
10.1175/2007jcli2065.1
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发表时间：
2008-08-01
影响因子：
4.9
通讯作者：
Schneider, Tapio
中科院分区：
文献类型：
--
作者：
O'Gorman, Paul A.;Schneider, Tapio
通过改变长波吸收器的光学厚度，用理想环流模型模拟了大范围的水循环和环流。虽然理想的GCM不能完全反映水文循环的复杂性，但模拟的气候范围很广，可以系统地发展和检验降水和水分输送如何随着气候变化而变化的理论。模拟结果表明，在不同气候条件下，水循环对长波光学厚度变化的响应特征不同。在较冷的气候条件下，全球平均降水量随地表温度线性增加，但在较高的地表温度下渐近达到最大值。辐射-对流平衡模拟再现了降水-温度关系的基本特征，包括线性状态的增长率。能量约束部分解释了降水-温度关系，但在定量上不准确。大尺度凝结在中纬度风暴路径中是最重要的，它的行为用水汽平流和凝结的随机模式来解释。与大尺度凝结相关的降水与平均比湿度不成比例，部分原因是随着气候变暖，凝结区域向上和经向移动，部分原因是平均凝结率取决于等熵比湿度梯度，而等熵比湿度梯度与比湿度本身不成比例。局地水汽收支将局地降水与蒸发和经向水汽通量联系起来，研究了其在副热带和温带的标度。在亚热带干燥区，蒸发和水分通量散度的相反变化之间保持着微妙的平衡。温带气候下，温带降水最大值沿着风暴路径移动，而在寒冷气候下，温带降水最大值位于风暴路径的赤道方向。
A wide range of hydrological cycles and general circulations was simulated with an idealized general circulation model (GCM) by varying the optical thickness of the longwave absorber. While the idealized GCM does not capture the full complexity of the hydrological cycle, the wide range of climates simulated allows the systematic development and testing of theories of how precipitation and moisture transport change as the climate changes. The simulations show that the character of the response of the hydrological cycle to variations in longwave optical thickness differs in different climate regimes.The global-mean precipitation increases linearly with surface temperature for colder climates, but it asymptotically approaches a maximum at higher surface temperatures. The basic features of the precipitation-temperature relation, including the rate of increase in the linear regime, are reproduced in radiative-convective equilibrium simulations. Energy constraints partially account for the precipitation-temperature relation but are not quantitatively accurate.Large-scale condensation is most important in the midlatitude storm tracks, and its behavior is accounted for using a stochastic model of moisture advection and condensation. The precipitation associated with large-scale condensation does not scale with mean specific humidity, partly because the condensation region moves upward and meridionally as the climate warms, and partly because the mean condensation rate depends on isentropic specific humidity gradients, which do not scale with the specific humidity itself.The local water vapor budget relates local precipitation to evaporation and meridional moisture fluxes, whose scaling in the subtropics and extratropics is examined. A delicate balance between opposing changes in evaporation and moisture flux divergence holds in the subtropical dry zones. The extratropical precipitation maximum follows the storm track in warm climates but lies equatorward of the storm track in cold climates.