Evaluation of an improved AROME configuration for fog forecasts during the SOFOG3D campaign.

Abstract

This paper evaluates fog forecasts of a new AROME configuration dedicated to fog thanks to observations of the recent field campaign SOuth westFOGs 3Dimensions (SOFOG3D). This new configuration takes advantage of an upgraded horizontal and vertical resolution, of a 2-moment microphysical scheme (LIMA) and of the inclusion of a parametrization of the droplets deposition onto vegetation. A statistical study conducted over the 6 months of the SOFOG3D field campaign allowed the evaluation of the quality of fog forecasts produced by this new configuration to compare it to the current operational configuration of AROME. The main findings are as follows: the new configuration forecast more fog events, with a few more false alarms, but improved the amount of fogs with low top height and with a low water content, underestimated by the reference configuration. The importance of the first level height for a good representation of the first few meters above the ground is crucial to improve the fog formation forecast. A delay of fog dissipation in the morning was highlighted in operational simulations and slightly reduced thanks to LIMA. This two-moment scheme produced thinner fogs, with less water content. These are more realistic, compared with observations, and thinner fog is also easier for solar radiation to dissipate.