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首页> 外文期刊>Weather and forecasting >A Review of Planetary Boundary Layer Parameterization Schemes and Their Sensitivity in Simulating Southeastern US Cold Season Severe Weather Environments
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A Review of Planetary Boundary Layer Parameterization Schemes and Their Sensitivity in Simulating Southeastern US Cold Season Severe Weather Environments

机译：行星边界层参数化方案及其在模拟美国东南部寒冷季节恶劣天气环境中的敏感性综述

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摘要

The representation of turbulent mixing within the lower troposphere is needed to accurately portray the vertical thermodynamic and kinematic profiles of the atmosphere in mesoscale model forecasts. For mesoscale models, turbulence is mostly a subgrid-scale process, but its presence in the planetary boundary layer (PBL) can directly modulate a simulation's depiction of mass fields relevant for forecast problems. The primary goal of this work is to review the various parameterization schemes that the Weather Research and Forecasting Model employs in its depiction of turbulent mixing (PBL schemes) in general, and is followed by an application to a severe weather environment. Each scheme represents mixing on a local and/or nonlocal basis. Local schemes only consider immediately adjacent vertical levels in the model, whereas nonlocal schemes can consider a deeper layer covering multiple levels in representing the effects of vertical mixing through the PBL. As an application, a pair of cold season severe weather events that occurred in the southeastern United States are examined. Such cases highlight the ambiguities of classically defined PBL schemes in a cold season severe weather environment, though characteristics of the PBL schemes are apparent in this case. Low-level lapse rates and storm-relative helicity are typically steeper and slightly smaller for nonlocal than local schemes, respectively. Nonlocal mixing is necessary to more accurately forecast the lower-tropospheric lapse rates within the warm sector of these events. While all schemes yield overestimations of mixed-layer convective available potential energy (MLCAPE), nonlocal schemes more strongly overestimate MLCAPE than do local schemes.
机译：需要用对流层下部的湍流混合来表示，以便在中尺度模型预报中准确描绘大气的垂直热力学和运动学特征。对于中尺度模型，湍流主要是亚网格尺度的过程，但是其在行星边界层（PBL）中的存在可以直接调制与预报问题相关的质量场的模拟描述。这项工作的主要目的是回顾天气研究和预报模型在描述湍流混合时通常采用的各种参数化方案（PBL方案），然后将其应用于恶劣的天气环境。每个方案代表在本地和/或非本地基础上的混合。局部方案仅考虑模型中紧邻的垂直层，而非局部方案可以考虑覆盖多个层的更深层，以表示通过PBL的垂直混合的影响。作为应用，研究了在美国东南部发生的一对寒冷季节的恶劣天气事件。尽管在这种情况下PBL方案的特征很明显，但这种情况凸显了在寒冷季节恶劣天气环境中经典定义的PBL方案的含混性。与本地方案相比，非本地方案的低级别失败率和风暴相对螺旋性通常分别更陡峭和稍小。为了更准确地预测这些事件的暖区内低层对流层漏失率，必须进行非本地混合。尽管所有方案都高估了混合层对流可用势能（MLCAPE），但非本地方案比本地方案更强烈地高估了MLCAPE。

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