Simulated Kelvin–Helmholtz Waves over Terrain and Their Microphysical Implications
Simulated Kelvin–Helmholtz Waves over Terrain and Their Microphysical Implications
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DOI：
10.1175/jas-d-18-0073.1
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发表时间：
2018-07
影响因子：
3.1
通讯作者：
Robert Conrick;C. Mass;Qi Zhong
中科院分区：
文献类型：
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作者：
Robert Conrick;C. Mass;Qi Zhong
利用奥林匹克山脉实验（OLYMPEX）野外活动的观测资料，模拟和评估了华盛顿州西部的两个开尔文-亥姆霍兹（KH）波事件。WRF-ARW模式对2015年12月12日和17日的事件进行了真实模拟，再现了嵌入KH波的中尺度环境、位置和结构，观测波长约为5 km。在这两种情况的模拟中，波浪都是从一个强烈切变层内的不稳定发展而来的，这种不稳定是由低层的东风气流被高空的西风所超越而引起的。在12月12日的事件中，低层东风是由奥林匹克山脉的阻挡造成的，而在17日的事件中，东风气流是由天气环境产生的。利用olymppex观测对这两种情况进行了模拟微物理评估。当KH波处于熔化水平时，模拟的微物理场，如水流星混合比，表现出相当大的振荡行为。相反，当波位于熔点以下时，微物理响应减弱。关闭模式的微物理方案和潜热导致KH波活动减弱，而去除奥林匹克山脉在12月12日事件中消除了KH波，但在12月17日事件中没有消除KH波。最后，对两个事件的几个微物理参数化对KH活性的影响进行了评估。
Two Kelvin–Helmholtz (KH) wave events over western Washington State were simulated and evaluated using observations from the Olympic Mountains Experiment (OLYMPEX) field campaign. The events, 12 and 17 December 2015, were simulated realistically by the WRF-ARW Model, duplicating the mesoscale environment, location, and structure of embedded KH waves, which had observed wavelengths of approximately 5 km. In simulations of both cases, waves developed from instability within an intense shear layer, caused by low-level easterly flow surmounted by westerly winds aloft. The low-level easterlies resulted from blocking by the Olympic Mountains in the 12 December case, while in the 17 December event, the easterly flow was produced by the synoptic environment. Simulated microphysics were evaluated for both cases using OLYMPEX observations. When the KH waves were within the melting level, simulated microphysical fields, such as hydrometeor mixing ratios, evinced considerable oscillatory behavior. In contrast, when waves were located below the melting level, the microphysical response was attenuated. Turning off the model’s microphysics scheme and latent heating resulted in weakened KH wave activity, while removing the Olympic Mountains eliminated KH waves in the 12 December event but not the 17 December case. Finally, the impact of several microphysics parameterizations on KH activity was evaluated for both events.