Logarithmic profile of temperature in sheared and unstably stratified atmospheric boundary layers
Logarithmic profile of temperature in sheared and unstably stratified atmospheric boundary layers
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DOI：
10.1103/physrevfluids.6.034606
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发表时间：
2021-03-11
影响因子：
2.7
通讯作者：
Gentine, Pierre
中科院分区：
文献类型：
--
作者：
Cheng, Yu;Li, Qi;Gentine, Pierre
浮力对低层大气中的平均速度、温度和标量浓度分布的影响通常在 MoninObukhov 相似理论 (MOST) 的框架内进行研究。 MOST 是几乎所有天气、气候和水文模型中地表大气交换参数化的理论基础。根据 MOST 的说法，随着浮力效应变得重要，平均速度和温度的经典对数分布就会被打破。然而，最近对湍流瑞利-贝纳德对流和沿垂直壁的自然对流的研究表明，近地表区域的平均温度仍然遵循对数分布。受这些新结果的启发，我们利用直接数值模拟和现场观测研究了剪切和不稳定分层大气边界层的平均位温剖面。我们发现，平均位温分布在很宽的稳定性参数范围内保持对数，这表征了浮力与剪切效应的相对重要性。与 MOST 相比，我们的结果表明，浮力不会改变平均位温剖面的对数性质，而是调节其斜率，该斜率不再具有普遍性，并且与 1/kappa 不同，其中 kappa 是冯卡门常数。这项研究为大气边界层中的标量湍流提供了另一个视角。
The impact of buoyancy on the mean velocity, temperature, and scalar concentration profiles in the lower atmosphere is typically investigated within the framework of MoninObukhov similarity theory (MOST). MOST is the theoretical foundation for parametrizing surface-atmosphere exchanges in nearly all weather, climate, and hydrological models. According to MOST, the classic logarithmic profiles of mean velocity and temperature break down as the buoyancy effects become important. However, recent studies on turbulent Rayleigh-Benard convection and natural convection along vertical walls suggest that the mean temperature in the near-surface region still follows a logarithmic profile. Motivated by these new results, we study the mean potential temperature profile in sheared and unstably stratified atmospheric boundary layers using direct numerical simulations and field observations. We find that the mean potential temperature profile remains logarithmic across a wide range of stability parameters, which characterizes the relative importance of buoyancy versus shear effects. Compared to MOST, our results suggest that the buoyancy force does not modify the logarithmic nature of the mean potential temperature profile, but instead modulates its slope, which is no longer universal and differs from 1/kappa, where kappa is the von Karman constant. This study provides another perspective on scalar turbulence in the atmospheric boundary layer.