Development of a new visibility parameterization based on the measurement of fog microphysics at a mountain site in Korea

Abstract

Fog (cloud) and drizzle microphysics were measured from July 2015 to September 2016 at the Cloud Physics Observation Site (CPOS), located at a mountainous region in Korea. In total 110 cloud/fog events were observed during this period. In detail, fogs at various stages, i.e., newly generated, developing, or dissipating stage were observed, along with some advected clouds with or without precipitation. Based on elaborate analyses of these extensive observation data, we propose a new visibility parameterization method. First, we compare previously developed visibility parameterization methods. Second, we propose a new visibility parameterization method that can be applied to typical fog and fog with precipitation. Uniquely to this new parameterization, the effective fog (cloud) droplet diameter data are utilized, along with liquid water content and droplet concentration that were utilized in previous studies. Third, we validate the accuracies of the previous and newly proposed visibility parameterization methods. The newly proposed visibility parameterization method is the most accurate (with a critical success index of 0.76), and it exhibits better performance than the direct Mie calculation method regardless of the values of effective droplet diameter.