How Well Does a Power Law Fit to a Diabatic Boundary-Layer Wind Profile?
How Well Does a Power Law Fit to a Diabatic Boundary-Layer Wind Profile?
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幂律与非绝热边界层风廓线的拟合效果如何？
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
Stefan Emeis
中科院分区：
文献类型：
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作者：
Stefan Emeis
两种类型的风廓线定律经常用于大气近地层：理论推导的对数廓线与非中性热层结的修正和经验推导的幂律。由于其数学上的简单性，幂律被广泛使用。本研究调查在何种情况下，幂律是一个很好的近似对数分布。在现有研究的扩展中，不仅对数和幂律剖面的斜率，而且曲率也应该一致。这种巧合是可能的粗糙度和分层条件的分析计算。对于中性和不稳定条件，幂律剖面的斜率和曲率不能与对数剖面的斜率和曲率重合。这只会发生在某些情况下，在一个稳定的分层流。本研究的实际结果是，幂律提供了一个很好的拟合对数轮廓稍微稳定的条件和非常光滑的表面。因此，幂律廓线可以很好地描述海上的风廓线，但在崎岖地形上则不然。
Two types of wind profile laws are frequently used for the atmospheric surface-layer: the theoretically derived logarithmic profile with corrections for non-neutral thermal stratification and the empirically derived power law. Due to its mathematical simplicity the power law is widely used. This study investigates in which situations the power law is a good approximation to the logarithmic profile. In extension to existing studies not only the slope of the logarithmic and the power law profiles but also the curvatures should coincide. The roughness and stratification conditions for which such a coincidence is possible are calculated analytically. For neutral and unstable conditions slope and curvature of a power law profile cannot coincide with that of the logarithmic profile. This can only happen under certain circumstances in a stably stratified flow. The practical result of this sudy is that the power law offers a good fit to the logarithmic profile for slightly stable conditions and for very smooth surfaces only. Thus the power law profile provides a good description of the wind profile over the sea but not over rough terrain.