摘要:夹卷混合过程作为影响云雾的主要物理过程之一，对云雾的生命周期、云雾降水的形成过程、辐射传输过程和气溶胶间接效应等都有着重要影响。本文从微物理和动力两个方面探讨辐射雾中的夹卷混合机制，既促进对夹卷混合机制的理论认识，又从新的角度来讨论辐射雾的发展消亡过程。利用2006年和2007年冬季在南京进行的雾综合观测的资料，研究了9个个例中的夹卷混合机制。首先，针对2007年12月10～11日这一次辐射雾过程进行详细分析，探讨了不同阶段微物理量的变化和夹卷混合机制。结果表明：成熟阶段主要为极端非均匀夹卷混合机制，数浓度和含水量同时减小，体积平均半径却基本保持不变；快速消散阶段主要为均匀夹卷混合机制，各微物理量同时减小，互为正相关关系。除了微物理，本文也分析了夹卷混合机制的动力特征，计算了过渡尺度数，发现在成熟（快速消散）阶段，过渡尺度数小（大），有利于极端非均匀（均匀）夹卷混合机制的发生。其次，分析了其他8个个例中微物理量之间的相关关系，发现体积平均半径和含水量之间主要呈正相关关系，以均匀夹卷混合为主。所得结果有助于夹卷混合机制参数化方案的开发，同时为辐射雾的模拟预报提供参考。
关键词:夹卷混合/
辐射雾/
微物理关系/
南京
Abstract:As one of the main processes affecting cloud and fog, the entrainment-mixing process has an important impact on the cloud/fog life cycle, precipitation formation, radiative transfer, aerosol indirect effect evaluation, and so on. This study discussed the entrainment-mixing mechanisms in a radiation fog from the microphysical and dynamical perspectives, which not only improved the theoretical understanding of entrainment-mixing mechanisms but also revealed the development and dissipation of radiation fog from a new perspective. Using the comprehensive field observational data in Nanjing during the 2006 and 2007 winter, entrainment-mixing mechanisms in nine fog cases were analyzed. First, a radiation fog event during December 10–11, 2007, was studied to understand the microphysical relationships and entrainment-mixing mechanisms during different phases in detail. Results showed that the extreme inhomogeneous entrainment-mixing was found in the mature phase, in which the volume-mean radius slightly changed as the number concentration and liquid water content decreased. The homogeneous entrainment-mixing was found in the rapid dissipation phase, in which all microphysical properties decreased simultaneously with positive correlations. Except for microphysical properties, the scale number was calculated as a dynamical measure for entrainment-mixing mechanisms. In the mature (rapid dissipation) phase, the scale number was small (large), indicating that the extreme inhomogeneous (homogeneous) entrainment-mixing was most likely to occur. The microphysical relationships of the other eight fog events were then examined, which indicated that the volume-mean radius had positive correlations with the liquid water content in general, i.e., homogeneous entrainment-mixing dominated. The research results were helpful to the development of parameterization schemes of entrainment-mixing mechanisms and provided a reference for the simulation and prediction of radiation fog.
Key words:Entrainment-mixing/
Radiation fog/
Microphysical relationships/
Nanjing
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