What Controls the Mean East-West Sea Surface Temperature Gradient in the Equatorial Pacific: The Role of Cloud Albedo
What Controls the Mean East-West Sea Surface Temperature Gradient in the Equatorial Pacific: The Role of Cloud Albedo
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DOI：
10.1175/jcli-d-13-00255.1
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发表时间：
2014-04-01
影响因子：
4.9
通讯作者：
Fedorov, A. V.
中科院分区：
文献类型：
--
作者：
Burls, N. J.;Fedorov, A. V.
沿赤道沿着东西海面的平均温度梯度是热带气候的一个重要特征。与大气步行者环流和海洋东西向温跃层倾斜紧密耦合，它有效地定义了热带气候条件。在太平洋，它的存在允许厄尔尼诺-南方涛动现象。因此，在完全耦合的海洋-大气系统中，是什么决定了这种温度梯度是气候动力学的一个中心问题，对于理解过去和未来的气候至关重要。利用一个综合耦合模式（Community Earth System Model（CESM）），作者论证了热带和中纬度之间的云系中的纬向梯度（Delta alpha）是如何决定赤道太平洋平均东西海面温度梯度的。在数值试验中，为了改变Δ α，作者通过修改大气水路径来改变云的光学性质，但只在模式的短波辐射方案中进行。当Δ α值在-0.15到0.1之间变化时，赤道太平洋的东西海温差从7.5 ℃减小到1 ℃以下，步行者环流几乎崩溃。这些实验揭示了三角洲α和纬向温度梯度之间的近线性关系，这通常与耦合模型相互比较项目第5阶段（CMIP 5）工业前控制模拟的结果一致。作者解释了这两个变量之间的密切关系，使用能量平衡模式，结合基本动力学的暖池，冷舌，和步行者环流复合体。
The mean east-west sea surface temperature gradient along the equator is a key feature of tropical climate. Tightly coupled to the atmospheric Walker circulation and the oceanic east-west thermocline tilt, it effectively defines tropical climate conditions. In the Pacific, its presence permits the El Nino-Southern Oscillation phenomenon. What determines this temperature gradient within the fully coupled ocean-atmosphere system is therefore a central question in climate dynamics, critical for understanding past and future climates. Using a comprehensive coupled model [Community Earth System Model (CESM)], the authors demonstrate how the meridional gradient in cloud albedo between the tropics and midlatitudes (Delta alpha) sets the mean east-west sea surface temperature gradient in the equatorial Pacific. To change Delta alpha in the numerical experiments, the authors change the optical properties of clouds by modifying the atmospheric water path, but only in the shortwave radiation scheme of the model. When Delta alpha is varied from approximately -0.15 to 0.1, the east-west SST contrast in the equatorial Pacific reduces from 7.5 degrees C to less than 1 degrees C and the Walker circulation nearly collapses. These experiments reveal a near-linear dependence between Delta alpha and the zonal temperature gradient, which generally agrees with results from the Coupled Model Intercomparison Project phase 5 (CMIP5) preindustrial control simulations. The authors explain the close relation between the two variables using an energy balance model incorporating the essential dynamics of the warm pool, cold tongue, and Walker circulation complex.