Thermodynamic Constraints on the Size Distributions of Tropical Clouds
Thermodynamic Constraints on the Size Distributions of Tropical Clouds
复制标题
热带云尺寸分布的热力学约束
DOI：
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
S. Krueger
中科院分区：
文献类型：
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作者：
T. Garrett;I. Glenn;S. Krueger
热带对流云的演变具有很大的时空尺度，这给数值模拟带来了困难。在这里，我们提出云的统计特性可以在云数n，饱和静态能量h和云周长λ的简化的时间无关坐标系中导出。在云边缘环流相互竞争总浮力能和空气的约束下，我们证明了云数和云周长的乘积nλ与λ不变量，并且云数与云边缘h λ相对于平均值的偏差呈负指数关系。总的来说，所有云的周长总和与大气静态稳定度的平方根成比例。这些理论结果表明，云场结构的复杂性可以从统计学上看作是大气整体热力学的一种突现性质。与一个详细的热带云场模拟的比较表明，一般的一致性≤ 13%。为了发展在高分辨率模拟中可检验的云时间演化的假设，热带云周长分布的形状被预测为随着气候变暖而不变，尽管总云量略有增加。
Tropical convective clouds evolve over a wide range of temporal and spatial scales, which makes them difficult to simulate numerically. Here we propose that cloud statistical properties can be derived within a simplified time‐independent coordinate system of cloud number n, saturated static energy h⋆, and cloud perimeter λ. Under the constraint that circulations around cloud edge compete with each other for total buoyant energy and air, we show that the product of cloud number and cloud perimeter nλ is invariant with λ and that cloud number follows a negative exponential with respect to cloud‐edge deviations of h⋆ with respect to the mean. Overall, the summed perimeter of all clouds scales as the square root of the atmospheric static stability. These theoretical results suggest that the complexity of cloud field structures can be viewed statistically as an emergent property of atmospheric bulk thermodynamics. Comparison with a detailed tropical cloud field simulation shows general agreement to within ≤13%. For the sake of developing hypotheses about cloud temporal evolution that are testable in high resolution simulations, the shapes of tropical cloud perimeter distributions are predicted to be invariant as climate warms, although with a modest increase in total cloud amount.