The selection of the planetary boundary layer (PBL) parameterisation schemes is crucial for the simulation of local meteorology, especially under extreme weather events. A suitable PBL scheme is one of the key conditions to accurately reproduce the real weather conditions. In this study, the performance of all the three available PBL schemes that can be coupled with the multi-layer urban canopy model in the Weather Research and Forecasting (WRF) model: Yonsei University (YSU), Mellor-Yamada-Janjic (MYJ), and Bougeault-Lacarrere (BL), is evaluated for a cold spell event with Guangdong-Hong Kong-Macao Greater Bay Area (GBA) as the study region. It is found that accurate prediction of the strength of the vertical mixing and the change in wind speeds over the upper atmosphere is critical for reproducing the nighttime temperatures during the cold spell. The simulations of the BL scheme are consistent with observations that wind speeds do not vary much during daytime and nighttime, thus exhibiting strong vertical mixing and slowing down the near-surface temperature decrease during nighttime. The MYJ and YSU schemes cause significant underestimation of the nighttime 2-m temperature due to significant overestimation of the nighttime upper-air wind speeds, which leads to more heat transport through horizontal advection and hinders vertical mixing and convective activities. The results confirm that selection of a suitable PBL scheme can effectively reduce the uncertainty of the simulation results, and the coupling of the BL scheme with the multi-layer urban canopy model can better simulate the cold spell events occurring in the GBA, which also provides valuable references for the simulation of other similar coastal cities.

中文翻译：

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利用WRF模拟粤港澳大湾区寒潮：对PBL方案的敏感性


行星边界层（PBL）参数化方案的选择对于当地气象模拟至关重要，特别是在极端天气事件下。合适的PBL方案是准确再现真实天气状况的关键条件之一。在本研究中，所有三个可用的 PBL 方案的性能都可以与天气研究和预报 (WRF) 模型中的多层城市冠层模型相结合：延世大学 (YSU)、Mellor-Yamada-Janjic (MYJ)和 Bougeault-Lacarrere (BL) 以粤港澳大湾区 (GBA) 为研究区域，对寒流事件进行评估。研究发现，准确预测垂直混合的强度和高层大气风速的变化对于再现寒潮期间的夜间温度至关重要。 BL方案的模拟结果与观测结果一致，即白天和夜间的风速变化不大，因此表现出强烈的垂直混合，减缓了夜间近地表温度的下降。 MYJ和YSU方案由于对夜间高空风速的显着高估而导致夜间2米温度的显着低估，从而导致更多的热量通过水平平流传输并阻碍垂直混合和对流活动。结果表明，选择合适的PBL方案可以有效降低模拟结果的不确定性，并且BL方案与多层城市冠层模型的耦合可以更好地模拟大湾区发生的寒潮事件，这也为对其他类似沿海城市的模拟具有参考价值。