A numerical study of mountain waves in the upper troposphere and lower stratosphere
A numerical study of mountain waves in the upper troposphere and lower stratosphere
复制标题
对流层上层和平流层下层山波的数值研究
DOI：
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发表时间：
2011
期刊：
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通讯作者：
V. Grubišić
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文献类型：
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作者：
A. Mahalov;M. Moustaoui;V. Grubišić
抽象的。对地形诱发转子实验 (T-REX) 的两个强化观测周期 (IOP) 中对流层上层和平流层下层 (UTLS) 的山波进行了数值研究。模拟使用天气研究和预报 (WRF) 模型以及由最精细的 WRF 巢驱动的微尺度模型。在 IOP8 期间，模拟结果揭示了 UTLS 中强垂直风切变区域中存在短波长扰动，从而导致动量通量反转。这些扰动的光谱特性以及随之而来的热和动量通量的垂直分布在对流层顶附近显示出强烈的发散，表明它们是由源自对流层下部的主要山波局部引起的沿切变线的切变不稳定性产生的。使用从微尺度模型获得的温度和风廓线进行初始化的理想化模拟结果进一步证实了这一点。对于 IOP6，我们分析了飞机测量中观察到的 O3 和 CO 的分布。它们显示出小规模的波动，其幅度和相位沿飞行路径变化。这些波动与观测到的垂直速度之间的详细比较表明，这些短波动的行为不仅归因于垂直运动，而且还归因于波浪演化的局部平均垂直梯度，该梯度受到较大变化的调制。微尺度模型模拟结果与现场无线电探空仪和飞机观测结果吻合良好。人们发现，微尺度模型提供的高垂直分辨率对于较小尺度过程的分辨率至关重要，例如与对流层中受困背风波相关的逆温层的形成，以及在平流层下部传播的山波。
Abstract. A numerical study of mountain waves in the Upper Troposphere and Lower Stratosphere (UTLS) is presented for two Intensive Observational Periods (IOPs) of the Terrain-induced Rotor Experiment (T-REX). The simulations use the Weather Research and Forecasting (WRF) model and a microscale model that is driven by the finest WRF nest. During IOP8, the simulation results reveal presence of perturbations with short wavelengths in zones of strong vertical wind shear in the UTLS that cause a reversal of momentum fluxes. The spectral properties of these perturbations and the attendant vertical profiles of heat and momentum fluxes show strong divergence near the tropopause indicating that they are generated by shear instability along shear lines locally induced by the primary mountain wave originating from the lower troposphere. This is further confirmed by results of an idealized simulation initialized with the temperature and wind profiles obtained from the microscale model. For IOP6, we analyze distributions of O3 and CO observed in aircraft measurements. They show small scale fluctuations with amplitudes and phases that vary along the path of the flight. Detailed comparisons between these fluctuations and the observed vertical velocity show that the behavior of these short fluctuations is due not only to the vertical motion, but also to the local mean vertical gradients where the waves evolve, which are modulated by larger variations. The microscale model simulation results show favorable agreement with in situ radiosonde and aircraft observations. The high vertical resolution offered by the microscale model is found to be critical for resolution of smaller scale processes such as formation of inversion layer associated with trapped lee waves in the troposphere, and propagating mountain waves in the lower stratosphere.