边界层湍流参数化改进对雾的模拟影响

为了提高边界层参数化在我国复杂下垫面上的描述能力，改善边界层能量和物质输送计算和检验其数值模拟效果，本文选取WRF三维模式，采用基于我国不同下垫面上的边界层观测资料改进的新MYNN（Mellor-Yamada-Nakanishi-Niino）参数化方案对2009年3月17日黄海海雾以及2011年12月4日华北地区两次大雾过程进行模拟检验，探讨边界层参数化方案对雾和边界层结构模拟的影响。参照卫星云图和探空资料，边界层内云水混合比垂直积分的水平分布的模拟能力明显提高，反映了改进的MYNN方案能够更好地模拟出两次雾过程的发生、移动和雾区空间分布，更精确的云水混合比和温度的垂直分布能更好地给出雾区的垂直结构和稳定层结，同时可改善雾区低层位温以及比湿垂直分布的模拟。

The Impact of an Improved Planetary Boundary Layer Parameteriza­tion Scheme on the Simulation of Fog

In order to improve the planetary boundary layer (PBL) parameterization over complex underlying surface for better calculation of vertical turbulent transport of energy and substances, and verify the effect in numerical simulation over China, an improved MYNN (Mellor-Yamada-Nakanishi-Niino) PBL parameterization scheme is selected in the WRF model to simulate two heavy fog cases that happened in the Yellow Sea on March 17th, 2009 and in North China on December 4th, 2011, respectively. The new MYNN scheme is tuned based on the observational PBL data over different underlying surfaces. In this paper, we attempt to simulate the evolution of both the land and sea fog events, and explore the boundary layer structure and the impact of the modified MYNN scheme on these simulations. With reference to the FY-3 satellite imageries and sounding data, it is found that better simulation of the horizontal distribution of the vertically integrated cloud water can lead to better simulation of generation, movement and spatial distribution of the heavy fog over both the ocean and land areas. The vertical profiles of temperature and mixing ratio of cloud water illustrate more reasonable vertical structure of the fog and the stable stratification. In addition, the new scheme improves the low-level vertical distribution of potential temperature and the specific humidity in the fog area.