High-resolution numerical studies on the effect of turbulence on the structure of nocturnal radiation fogs

雾作为一种气象现象，通过降低大气边界层的能见度，对经济和人身安全都会产生强烈的影响。与空中、海上和陆地运输相关的雾造成的总经济损失与冬季风暴相当。尽管有大量关于雾的研究文献，但我们对导致雾形成的物理过程及其微观结构的了解仍然是片面的。这是因为许多复杂的过程，如辐射冷却、湍流混合和雾的微物理相互作用是非线性的。此外，地表植被和土壤特性的异质性进一步增加了雾的可预测性。因此，数值天气预报模式的雾预报能力仍然较差。在本项目中，将使用高分辨率大涡模拟(LES)来研究湍流对夜间辐射雾的影响。LES模式Palm将在1m量级上以非常高的分辨率使用，同时使用欧拉体积云物理方案和嵌入的拉格朗日粒子模型，该模型允许显式地解析气溶胶和雾滴。这一创新的方法首次允许研究雾滴湍流与大涡模拟的相互作用。本文的目的是研究夜间雾层对早晨过渡和白天边界层的影响。此外，地面非均匀对夜间辐射雾的影响将通过LES的规定的理想化规则和观测到的不规则地面不均匀来研究。模拟数据将被强迫，并用来自卡博(荷兰)和林登堡(德国)的超级站点的观测数据进行验证。

Fog as a meteorological phenomenon can have a strong impact on the economy but al-so on personal safety by reducing the visibility in the atmospheric boundary layer. Totaleconomic losses associated with fog on aviation, marine and land transportation are comparable to those of winter storms. Despite the fact that there is abundant literature on fog research, our knowledge about the physical processes that lead to fog formation and its microstructure remains partial. This is due to the fact that many complex processes like radiative cooling, turbulent mixing and the microphysics of fog interact non-linearly with each other. Moreover, surface heterogeneity regarding vegetation and soil characteristics further complicate the predictability of fog. Consequently, the fog forecasting capability of numerical weather prediction models is still poor. In this project, high-resolution large-eddy simulations (LES) will be used to investigate the effect of turbulence on nocturnal radiation fogs. The LES model PALM will be used at very high resolution in the order of 1 m with both an Eulerian bulk cloud physics scheme and an embedded Lagrangian particle model that allows for explicitly resolving aerosols and fog droplets will be employed. This innovative approach allows for studying fog droplet turbulence interactions for the first time with LES. The aim of this study is to study the effect of a nocturnal fog layer on the morning transition and the daytime boundarylayer. Moreover, the effect of surface heterogeneity on nocturnal radiation fog will beinvestigated by means of LES with prescribed idealized regular and observed irregular surface heterogeneities. The simulation data will be forced and validated with observational data from the super-sites at Cabauw (The Netherlands) and Lindenberg (Germany).