Enhanced Nighttime Fog and Low Stratus Occurrence Over the Landes Forest, France

Abstract

Understanding the drivers of fog and low stratus (FLS) cloud occurrence is important for traffic, ecosystems, and climate models, but it is challenging to analyze due to the complex interactions between meteorological factors and land cover. Here, we use active and passive satellite data, as well as reanalysis data to investigate nighttime FLS occurrence over the expansive Landes forest in France from 2006 to 2015. We find significant FLS enhancement over the forest compared to surrounding areas, especially in summer and fall. Lower wind speed and lower temperatures are found over the forest at night, which can enhance FLS development over the forest. Still, other drivers, such as biovolatile organic compounds acting as cloud condensation nuclei, are most likely important as well. The results show that the influence of forests on boundary layer clouds is not limited to convective daytime conditions.