Investigating the Effect of Anthropogenic Fire Ritual on Cloud Microphysics in Current Scenario: A Novel Study on Aerosol-Cloud Interaction

Abstract

The Indian anthropogenic fire ritual called Yajna has been practiced since ancient times. The production of a significant amount of aerosols is one aspect of large-scale Yajna that could increase the cloud condensation nuclei (CCN) in the atmosphere then subsequently enhance rain processes by creating low-level rain clouds and interacting with pre-existing clouds. In present study, we tried to explore the scientific basis of aforesaid hypothesis using satellite datasets. The chemical composition and hygroscopicity (estimated κ: 0.06-0.8) of the Yajna-induced particles led the formation of more cloud droplets, which in turn would have accelerated the collision-coalescence process and turned into raindrops. Meerut City in India is one of the cases where large scale Yajna was carried out for a week in March 2018. The Yajna event led to emission of ~ (8.4 ± 1.5) ×1019 to (3.08 ± 2.5) ×1020 CCN particles which gave rise to precipitation signature (~0.4 mm/day) of a very light rain category in the surrounding area based on satellite data. This precipitation could be due to i) initiation of collision coalescence process even in a lower cloud liquid water path (LWP) i.e. 20-86 g/m2 and ii) formation of ice cloud with lower altitude centroid. Precipitation in such a condition is not a general phenomenon because the same has been earlier reported to be suppressed (especially in case of forest fires) in presence of high aerosol concentration and lower LWP. We have discussed micro scientific insights of Yajna that could be helpful to better understand its effect on the cloud microphysical
processes. However, more such studies are required in future to validate aforesaid complex interactions.