Climatic trends in fog occurrence over the Indo-Gangetic plains

The Indo-Gangetic plains (IGP) in India witness widespread fog during winter months of December-January-February (DJF) since 1970s at temperatures between 5 and 20 degrees C. Despite its vast spatial extent, the localized physical nature of fog over various time and space scales limits successful attempts of its accurate prediction. This poses a challenge towards reducing calamities and huge economic losses associated with the consequent visibility degradation. Increasing rate of urbanization and both enhanced natural and anthropogenic forcing influence fog formation, persistence, and dissipation. It is imperative to understand the associated changes in fog trends to ascertain the effect of these forcing on fog and quantify its prediction. Therefore, the trends in fog occurrence over the Indo-Gangetic plains are assessed for a period of 37 years from 1977/1978-2013/2014 (DJF). A statistically significant increasing trend in fog frequency is found to be related to changes in associated meteorological parameters. The shift of visibility around year of 1998 is indicated by important changes occurred in temperature, humidity, and wind speed. Distinct patterns before and after 1998 are observed for fog visibility conditions and that may have significant implications for weather forecasts and local climate change.