WRF Model Prediction of a Dense Fog Event Occurred During the Winter Fog Experiment (WIFEX)

In this study, the sensitivity of the Weather Research and Forecasting (WRF) model to simulate the life cycle of a dense fog event that occurred on 23–24 January 2016 is evaluated using different model configurations. For the first time, intensive observational periods (IOPs) were made during the unique winter fog experiment (WIFEX) that took place over Delhi, India, where air quality is serious during the winter months. The multiple sensitivity experiments to evaluate the WRF model performance included parameters such as initial model and boundary conditions, vertical resolution in the lower boundary layer (BL), and the planetary BL (PBL) physical parameterizations. In addition, the model sensitivity was tested using various configurations that included domain size and grid resolution. Results showed that simulations with a high number of vertical levels within the lower PBL height (i.e., 10 levels below 300 m) simulated the accurate timing of fog formation, development, and dissipation. On the other hand, simulations with less vertical levels in the PBL captured only the mature physical characteristics of the fog cycle. A comparison of six local PBL schemes showed little variation in the onset of fog life cycle in comparison to observations of visibility. However, comparisons of observations with thermodynamical values such as 2-m temperature and longwave radiation showed poor relationships. Overall, quasi-normal scale elimination (QNSE) and MYNN 2.5 PBL schemes simulated the complete fog life cycle correctly with high liquid water content (LWC; 0.5/0.35 g m⁻³), while other schemes only responded during the mature phase.