Land-atmosphere interactions and the multi-scale variability of fog in a complex physiographic environment

The significant spatio-temporal variability in fog characteristics represents a major factor in our ongoing difficulty with providing accurate fog forecasts for specific locations such as airports, maritime ports and roads. The sensitive nature of fog to numerous environmental conditions is such that severely reduced visibility conditions may be observed at one location while clear conditions prevail nearby. Variability in the life cycle of fog is observed over a wide spectrum of temporal and spatial scales and is highly dependent on the spatial distribution of land-surface properties such as temperature, aerodynamic roughness and soil moisture. This dependency is studied through 3D mesoscale numerical simulations of observed fog cases in the Paris area. The interactions among key boundary layer processes driving the fog's variability are described.