Observed versus simulated mountain waves over Scandinavia – improvement of vertical winds, energy and momentum fluxes by enhanced model resolution?
Observed versus simulated mountain waves over Scandinavia – improvement of vertical winds, energy and momentum fluxes by enhanced model resolution?
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DOI：
10.5194/acp-17-4031-2017
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发表时间：
2017-03
影响因子：
6.3
通讯作者：
J. Wagner;A. Dörnbrack;M. Rapp;S. Gisinger;Benedikt Ehard;M. Bramberger;B. Witschas;F. Chouza;S. Rahm;C. Mallaun;G. Baumgarten;P. Hoor
中科院分区：
文献类型：
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作者：
J. Wagner;A. Dörnbrack;M. Rapp;S. Gisinger;Benedikt Ehard;M. Bramberger;B. Witschas;F. Chouza;S. Rahm;C. Mallaun;G. Baumgarten;P. Hoor
抽象的。利用机载观测资料和水平网格尺寸分别为16、7.2、2.4和0.8 km的全球和中尺度数值模拟，对2013年12月发生在斯堪的纳维亚半岛北方的两次山波事件进行了分析。在这两次事件中，西风越山流引起的向上传播的山波与不同的波的特点，由于不同的大气背景条件。虽然在第一次事件中，由于平流层风弱，波浪在25至30公里之间的高度发生破碎，但在第二次事件中，波浪传播到30公里以上的高度，并在对流层的平流层侵入层中形成界面波。全球和中尺度模拟与16和7.2公里的网格大小无法正确地模拟山波的振幅和波长，由于未解决的山峰。在2.4和0.8公里的水平分辨率的模拟，山波的水平波长大于15公里的解决，但表现出太小的振幅和太高的能量和动量通量。模拟通量可以通过增加垂直模型网格分辨率或通过增强模型中的湍流扩散来减少，这与小尺度非线性波效应的改进表示法相当。
Abstract. Two mountain wave events, which occurred over northern Scandinavia in December 2013 are analysed by means of airborne observations and global and mesoscale numerical simulations with horizontal mesh sizes of 16, 7.2, 2.4 and 0.8 km. During both events westerly cross-mountain flow induced upward-propagating mountain waves with different wave characteristics due to differing atmospheric background conditions. While wave breaking occurred at altitudes between 25 and 30 km during the first event due to weak stratospheric winds, waves propagated to altitudes above 30 km and interfacial waves formed in the troposphere at a stratospheric intrusion layer during the second event. Global and mesoscale simulations with 16 and 7.2 km grid sizes were not able to simulate the amplitudes and wavelengths of the mountain waves correctly due to unresolved mountain peaks. In simulations with 2.4 and 0.8 km horizontal resolution, mountain waves with horizontal wavelengths larger than 15 km were resolved, but exhibited too small amplitudes and too high energy and momentum fluxes. Simulated fluxes could be reduced by either increasing the vertical model grid resolution or by enhancing turbulent diffusion in the model, which is comparable to an improved representation of small-scale nonlinear wave effects.