High-Resolution GEM-LAM Application in Marine Fog Prediction: Evaluation and Diagnosis

Abstract

A three-level nested rendering of a high-resolution limited-area model version of the Global Environment Multiscale configuration (GEM-LAM), running quasi-operationally at the Canadian Meteorological Centre, is evaluated for its capabilities in marine fog prediction. The model shows a general underestimation of the cloud water content at lower levels that is utilized as one of the proxies for fog and/or low stratus. A warm and dry tendency also appears at the lowest layer (a few hundreds of meters above the surface) of the vertical profiles and at screen level. The condensation scheme directly generates/dissipates the cloud water content (or fog) while boundary layer processes [such as moist turbulent kinetic energy (MoisTKE)] vertically redistribute it. However, the results presented here emphasize the significance of the accurate initial and vertical velocity fields, as well as the interactions between the condensation scheme and the radiation scheme that interacts fully with clouds. These conclusions suggest that a delicate balance among the different physical processes and dynamics is needed for a successful fog forecast.