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

Abstract

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° 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 × 108 to 2.2 × 108 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.

Challenges in Simulating Prevailing Fog Types Over Urban Region of Delhi

“…The frequency of a northwest/west wind pattern was significantly correlated (84%) with the existence of these positive ΔRH/ΔZ fog episodes. A recent study by Verma et al (2022) have reported that the rivers such as Indus, Chinab, and Ravi, along with the Arabian Sea, play a crucial role in augmenting water vapor levels over the IGP region by 19 ± 5%, thereby facilitating the intensification of fog and haze through the aerosolwater vapor interaction. Furthermore, the vast agricultural land adjacent to riparian areas and canals can significantly enhance moisture in the atmospheric boundary layer through processes such as evaporation and evapotranspiration (Devanand et al, 2019;Guo et al, 2022).…”

Unraveling the Mechanism of the Holes in the Blanket of Fog Over the Indo‐Gangetic Plains: Are They Driven by Urban Heat Islands or Aerosol?

“…Widespread dense haze and fog blankets the Indo‐Gangetic plains (IGP) of the northern India mostly during the December‐February time‐period with around 60% of low visibility days. This unique regional‐scale weather phenomenon reduces the surface visibility to less than 50–100 m and causes delay/diversion of the trains and flights, contributes to vehicular accidents, as well as degrade the air quality (Ghude et al., 2023; Verma et al., 2022). The widespread dense fog events are influenced by the thick layer of aerosols experienced by the IGP during the winter season, which are also responsible for extensive aerosol‐induced health impacts (Amarendra Singh et al., 2022).…”

Solving the mysteries of Lahore smog: the fifth season in the country

“…The meteorological and topographic features of the study region also support the accumulation and retention of air pollutants. The highly irrigated region of the Indo-Gangetic Plain (IGP) provides abundant cloud condensation nuclei (loose alluvial sediments and high anthropogenic activities), plenty of moisture for the accumulation of air pollutants (Mishra et al, 2020;Ojha et al, 2020;Verma et al, 2022). This is further strengthened by the stable meteorology and the "valley effect" created by the topographical features (Hindukush-Karakoram-Himalaya Mountain ranges) and is most prominent during the post-monsoon and winter seasons (Resmi et al, 2019).…”