Assessing the influence of complex terrain on severe convective environments in northeastern Alabama
Assessing the influence of complex terrain on severe convective environments in northeastern Alabama
复制标题
评估复杂地形对阿拉巴马州东北部强对流环境的影响
DOI：
10.1175/waf-d-20-0136.1
复制
发表时间：
2021
影响因子：
2.9
通讯作者：
Markowski, Paul
中科院分区：
文献类型：
--
作者：
Katona, Branden;Markowski, Paul
穿越复杂地形的风暴可能会遇到快速变化的对流环境。然而，我们对对流风暴环境中地形引起的变化的理解仍然有限。HRRR数据被用来创建流行的对流风暴预报参数为不同的风况的气候。自组织映射（SOM）被用来产生六个不同的低层风制度，其特征在于不同的风向，其中流行的不稳定性和垂直风切变参数的平均值。气候表明，不稳定性和垂直风切变是高度可变的地区的复杂地形，扰动相对于地形的空间分布依赖于低层风向。理想化的模拟被用来调查的SOM气候中看到的一些扰动的起源。理想化的模拟复制了SOM气候学中的许多特征，这有助于分析其动力起源。当风近似垂直于地形时，地形的影响最大。在这种情况下，背风面会形成驻波，导致低层风速增加，与高原山谷背风面的垂直风切变减少。此外，在边界层内相对湿度局部降低的地形背风面，CAPE趋于降低，LCL高度增加。
Storms crossing complex terrain can potentially encounter rapidly changing convective environments. However, our understanding of terrain-induced variability in convective storm environments remains limited. HRRR data are used to create climatologies of popular convective storm forecasting parameters for different wind regimes. Self-organizing maps (SOMs) are used to generate six different low-level wind regimes, characterized by different wind directions, for which popular instability and vertical wind shear parameters are averaged. The climatologies show that both instability and vertical wind shear are highly variable in regions of complex terrain, and that the spatial distributions of perturbations relative to the terrain are dependent on the low-level wind direction. Idealized simulations are used to investigate the origins of some of the perturbations seen in the SOM climatologies. The idealized simulations replicate many of the features in the SOM climatologies, which facilitates analysis of their dynamical origins. Terrain influences are greatest when winds are approximately perpendicular to the terrain. In such cases, a standing wave can develop in the lee, leading to an increase in low-level wind speed and a reduction in vertical wind shear with the valley lee of the plateau. Additionally, CAPE tends to be decreased and LCL heights are increased in the lee of the terrain where relative humidity within the boundary layer is locally decreased.