Role of turbulence, radiation, and land surface-atmosphere exchange in modeling radiation fog in the Netherlands

The proper forecasting of the occurrence of radiation fog is still one of the challenging topics in boundary-layer meteorology, despite its high societal importance like for aviation and road traffic. In fact radiation fog depends on many processes that all critically interact on relatively short time scales. Goal of this study is to evaluate the performance of two state-of-the-art meso-scale atmospheric models in forecasting the onset and development of radiation fog episodes in the Netherlands. This study is a follow-up of the study by Van de Velde et al. (2010). However, in contrast to Van der Velde et al. (2010) our study focuses on fogs that occur in relatively warm atmospheric conditions. The meso-scale models involved are the widely used Weather Research Forecasting (WRF-version 3.3) model and HARMONIE. The spatial extent of the fog forecasted by the models is evaluated using measurements taken at SYNOP stations throughout the Netherlands. To study the vertical distribution of the fog-related quantities, detailed measurements taken at the Cabauw measurement facility are used. It appears that both the WRF model and the HARMONIE model have severe problems in forecasting both the onset and the duration of the fog layer at different locations. A detailed analysis using the WRF model reveals that the results depend heavily on model physics, most notably the radiation scheme, the parameterization of turbulent transfer within the Atmospheric Boundary Layer and the land-atmosphere exchange scheme. The results also appear to be sensitive to the details of the numerical setup of the experiment such as the extension of the domain and the horizontal and vertical resolution.

Reference: Van de Velde, I.R, G.J. Steenevel, B.G.J. Wichers Schreur, and A.A.M. Holtslag, 2010: Modeling and forecasting the onset and duration of severe radiation fog under frost conditions. Mon Wea. Rev., 138, 4237-4253.