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Atmospheric oscillations drive winter aerosol variability over the Indo-Gangetic Plain
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DOI：10.1007/s00382-026-08348-0.png)
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Abstract
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Both natural processes and anthropogenic activities contribute to atmospheric aerosol loading, but their relative fractions vary significantly across regions and seasons. Despite the complexity, accurate delineation of these two factors remains indispensable for the legitimate assessment of aerosol impacts and formulation of effective air-pollution control and mitigation strategies. Indo-Gangetic Plain (IGP) is one of the densely populated regions in the world, which is prone to anthropogenic aerosol contribution due to expedited urbanisation, where the effects of natural processes on aerosol abundance and variability are often overlooked. Aerosol optical depth over the IGP in winter is 60% higher than its seasonal mean value over India, but exhibits large variability. Our analysis using more than two-decades of satellite-based measurements unambiguously demonstrates that atmospheric oscillations drive wintertime aerosol variability over the IGP. During their prominent positive phases, oscillations with 5–10-day, 10–20-day and 20–40-day periodicities account for 16%, 17% and 17% enhancement in AOD, respectively. The variability in aerosol concentration is intensified further when the oscillations are in phase. Modifications in the pressure fields, associated with these oscillations, lead to strengthening and weakening of winds, resulting in dispersal and accumulation of aerosols. Consequent AOD variations during the positive and negative phases of the oscillations are further amplified by the contrasting changes in humidity conditions. While the oscillations with 5–10-day periodicity are associated with the eastward propagating Western Disturbances, those with 10–20-day and 20–40-day periodicities are due to the westward migration of pressure systems, connected with Quasi-biweekly oscillations and Rossby wave trains, respectively. The findings in this study are vital for improving the model forecast accuracy of haze/fog events and addressing the regional and global air-pollution challenges.
Keywords:
Atmospheric oscillations
Aerosol
Indo-Gangetic Plain
Winter haze
Circulation dynamics
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