The Role of Cloud Condensation Nuclei in Fog Modeling

A key point of the modeling of the formation, duration, and dissipation of fog is to understand the activation processes of cloud condensation nuclei (CCN) and the subsequent droplet development.

One of the most widely used models, the Weather Research and Forecasting (WRF) model, was evaluated with the purpose of analyzing its ability to simulate microphysical processes. The WSM3 and CAM 5.1 microphysical parameterizations were used, yielding good results for the modeling of radiation, advection and frontal fog in the Mexico Basin.

The CCNs activation conditions were characterized through the analysis of the WRF microphysical parameterizations, the input aerosol species and the typical activation parameters, such as temperature and humidity. The results for the number concentration of cloud droplets, liquid water content and visibility simulated for case studies in the Basin of Mexico were found to be within the typical ranges reported by other authors. Particularly, the mean volume diameter, a good indicator of the development of fog droplets, ranged between 7 to 14 µm, typical values found in radiation and advection fogs.