Atmospheric rivers fueling the intensification of fog and haze over Indo-Gangetic Plains

Indo-Gangetic Plains (IGP) experiences persistent and widespread rise of fog and haze during the winter season. This has been attributed to the rise in pollution levels and water vapor, but the reason for enhancement in latter is not clear yet. We detect moisture incursion from Arabian Sea, a phenomenon called atmospheric rivers (AR), land-falling intermittently along 12-25 degrees N corridor of the west-coast of India during winter; using satellite and reanalysis data. The total vertically integrated horizontal water vapor transport in AR-landfalls ranging from 0.7 x 10(8) to 2.2 x 10(8) kg/s; nearly five-orders of magnitude larger than the average discharge of liquid water from Indus River into Arabian Sea. These AR events are playing prominent role in enhancing water vapor over IGP region by 19 +/- 5%; in turn fueling the intensification of fog and haze through aerosol-water vapor interaction. We found that AR events enhanced aerosol optical depths over IGP by about 29 +/- 13%. The progression of moist-laden winds in ARs onto Himalayan Mountains contributes to the precipitation that explains the observed rise in the extreme flow of western Himalayan Rivers in winter. We conclude that these ARs likely contribute to the decline of snow albedo as pollution-mixed-ARs encounter Hindukush-Karakoram-Himalayan mountain region.

Automated summary

The Indo-Gangetic Plains (IGP) experience persistent and widespread fog and haze during the winter season, which is attributed to the rise in pollution levels and water vapor. This study detects moisture incursion from the Arabian Sea, known as atmospheric rivers (AR), which intermittently land-fall along the west coast of India during winter. These AR events significantly enhance water vapor over the IGP region, fueling the intensification of fog and haze through aerosol-water vapor interaction. The study also finds that the moist-laden winds in ARs contribute to precipitation in the Himalayan Mountains, explaining the observed rise in western Himalayan river flow during winter.