Evaluating models of the neutral, barotropic planetary boundary layer using integral measures: Part I. Overview
Evaluating models of the neutral, barotropic planetary boundary layer using integral measures: Part I. Overview
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DOI：
10.1023/a:1016521215844
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发表时间：
2002-09-01
影响因子：
4.3
通讯作者：
Garratt, JR
中科院分区：
文献类型：
--
作者：
Hess, GD;Garratt, JR
利用气象野外试验获得的交叉等压角alpha(0)、地转阻力系数C-g和rosby数相似理论的函数A和B等数据，对中性正压行星边界层的一系列模式进行了评价。数据给出了α(0)、C-g和边界层上的积分耗散率作为表面罗斯比数的函数的明确关系。Lettau的一阶闭包混合长度模型能很好地拟合数据；其他简单的模型给出了合理的一致性。然而，更复杂的模型，如高阶闭合、大涡模拟、直接数值模拟和实验室模型，对数据的拟合效果较差。简单模式在湍流闭合中（至少）有一个与大气观测相匹配的自由参数；更复杂的模型要么基于更一般的流，要么没有自由的闭包参数。这表明，我们所能找到的所有大气实验都违反了复杂模式所要求的稳定、均匀、中性、正压流的严格简化假设。角(0)比C-g对假设的违反更敏感。数据的行为在三个纬度范围内是不同的。在中高纬度地区，A和B的观测值几乎不受纬度的影响；最好的估计是A = 1.3和B = 4.4。在低纬度地区，中性的正压性罗斯比数论失效了。B的值向赤道方向增大；A的测定是不明确的——向赤道方向的趋势可能增加或减少。在大约5度和30度纬度之间，数据的分散被认为主要是由于固有的斜压性的存在。信风逆温的存在、热不稳定和地球自转的水平分量Omega(H)也有贡献。当科里奥利参数\f\趋近于零时，A和B值的显著变化发生在赤道和大约5度纬度之间的区域。虽然A和B随纬度的变化表明与直接数值模拟得到的结果有一些相似之处，但由于实际大气中存在未包括在数值模式中的额外复杂性，因此无法进行有意义的直接比较。
Data for the cross-isobaric angle alpha(0), the geostrophic drag coefficient C-g, and the functions A and B of Rossby number similarity theory, obtained from meteorological field experiments, are used to evaluate a range of models of the neutral, barotropic planetary boundary layer. The data give well-defined relationships for alpha(0), C-g, and the integrated dissipation rate over the boundary layer, as a function of the surface Rossby number. Lettau's first-order closure mixing-length model gives an excellent fit to the data; other simple models give reasonable agreement. However more sophisticated models, e.g., higher-order closure, large-eddy simulation, direct numerical simulation and laboratory models, give poor fits to the data. The simple models have (at least) one free parameter in their turbulence closure that is matched to atmospheric observations; the more sophisticated models either base their closure on more general flows or have no free closure parameters. It is suggested that all of the atmospheric experiments that we could locate violate the strict simplifying assumptions of steady, homogeneous, neutral, barotropic flow required by the sophisticated models. The angle alpha(0) is more sensitive to violations of the assumptions than is C-g.The behaviour of the data varies in three latitude regimes. In middle and high latitudes the observed values of A and B exhibit little latitudinal dependence; the best estimates are A = 1.3 and B = 4.4. In lower latitudes the neutral, barotropic Rossby number theory breaks down. The value of B increases towards the Equator; the determination of A is ambiguous - the trend can increase or decrease towards the Equator. Between approximately 5degrees and 30degrees latitude, the scatter in the data is thought to be primarily due to the inherent presence of baroclinicity. The presence of the trade-wind inversion, thermal instability and the horizontal component of the Earth's rotation Omega(H) also contribute. Marked changes in the values of A and B occur in the region between the Equator and approximately 5degrees latitude, as the Coriolis parameter \f\ approaches zero. Although the variation of A and B with latitude suggests some similarity to the results obtained from the direct numerical simulations, the presence of additional complexities in the real atmosphere that are not included in the numerical model, precludes a meaningful direct comparison.