Numerical Simulation of a Fog Event with a One-Dimensional Boundary Layer Model

Abstract

A one-dimensional boundary layer model is used to simulate a fog event. This model describes the condensation process at subgrid-scale, the gravitational settling of fog droplets and their interactions with solar and thermal radiation, as well as the turbulent transport associated with turbulent kinetic energy. The different parameterizations used are rather simple, aimed at operational forecasting. Computed results are compared to the measurements of a fog event at Cabauw in the Netherlands on 3 August 1977. The model seems to be able to describe the mechanisms occurring in fog evolution from its appearance to its disappearance. The dataset is the most complete ever published, but as yet it is difficult to validate the different parameterizations. Nevertheless, the importance of turbulent transport is pointed out again. The sensitivity of the model to thermal cooling, the gravitational setting velocity and the initial data is described together with the usefulness of subgrid-scale parameterization. In this work emphasis has been paced on the quantitative comparison between computed and observed evolutions.