- 1Indian Institute of Tropical Meteorology, Pune, India
- 2Dept. of Atmospheric and Space Sciences, Savitribai Phule Pune University, Pune, India
- 3Institute of Geography and Earth Sciences, University of Pécs, Pécs, Hungary
- 4National Centre for Medium Range Weather Forecasting, Uttar Pradesh, India
Understanding fog microphysics involves examining the size distribution, chemical composition, and hygroscopic properties of aerosols, which influence their activation as cloud condensation nuclei (CCN) and contribute to fog droplet formation. Incorporating these aerosol-driven processes into Numerical Weather Prediction (NWP) models, such as the Weather Research and Forecasting (WRF) model, has proven essential for accurately simulating fog development, sustainment, and dissipation.
India's current operational fog forecasting systems, particularly for urban regions, often lack detailed aerosol representation. The present study integrates water-friendly and carbonaceous aerosols using climatological data (2001–2007) within the Thompson-Eidhammer Aerosol-Aware Microphysics scheme in the WRF model to enhance fog forecasting for Delhi. The system incorporates improved CCN activation to capture the vertical development of fog.
To evaluate model performance, a 10-day winter spell during the 2024–25 season was selected, including hazy conditions and dense fog events. The selected period featured two hazy days with surface visibility oscillating around 1000 meters and seven fog episodes, including four dense radiation fog events and three cloud base-lowering fog occurrences. Model validation of key meteorological variables such as 2 m temperature (T2), relative humidity (RH2), and radiative fluxes (shortwave and longwave) shows strong agreement with ground-based measurements from the Winter Fog Experiment (WiFEX) at Indira Gandhi International Airport (IGI), Delhi.
Additionally, the study introduces the development of the visibility parameterization based on aerosol extinction coefficients and cloud water mixing ratios. This diagnostic approach in the WRF model effectively captures visibility degradation due to hygroscopic aerosols under hazy conditions and during the initial phases of fog formation. The findings underscore the importance of aerosol-aware modeling in urban fog forecasting and contribute to improving visibility diagnostics.
Preliminary results from this research will be presented at the EGU 2025 conference.
How to cite: Kumar, S., Parde, A. N., Peterka, A., Geresdi, I., Pakkattil, A., Govardhan, G., and Ghude, S. D.: Aerosol Based Fog Forecasting System and Visibility Parameterization For Delhi and NCR , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7865, https://doi.org/10.5194/egusphere-egu25-7865, 2025.
