How do aerosols influence the formation and persistence of winter fog in North India?

Aerosols are tiny solid or liquid particles suspended in the atmosphere, originating from sources like vehicles, industries, crop burning, and natural processes. In North India, especially during winter, high concentrations of aerosols combine with meteorological conditions to significantly influence the formation and persistence of fog.

• Nucleation Sites for Fog Droplets: Aerosols act as condensation nuclei, around which water vapor condenses more readily. This leads to the formation of more, but smaller, fog droplets, making the fog denser and reducing visibility.
• Enhanced Fog Thickness and Persistence: The increased number of fog droplets due to aerosols causes fog to become thicker and persist for longer durations. The smaller droplets are less likely to settle or evaporate quickly, prolonging foggy conditions.
• Reduction of Solar Radiation: Aerosols scatter and absorb sunlight, reducing the amount of solar radiation reaching the ground. This lowers surface temperatures, further supporting the persistence of fog by slowing down the evaporation process.
• Interaction with Pollutants: Aerosols can absorb pollutants like SO2 and NOx, leading to chemical reactions that may further stabilize fog droplets and increase their longevity.
• Implications for Air Quality: Fog traps pollutants near the ground, worsening air quality and leading to health hazards such as respiratory problems, especially for vulnerable groups.
• Impact on Daily Life: Persistent and dense fog disrupts transportation (road, rail, air), causes accidents, delays, and affects economic activities. It also increases energy consumption as people use more heating and lighting.