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<p>The Indo-Gangetic Plain has emerged as a major global hot spot of wintertime particulate pollution. This is especially evident in Northeastern Pakistan, where cities like Lahore are now recording increasingly extreme smog levels. In this study, we establish the smog formation process over the larger Indo-Gangetic Plain with a focus on Lahore. Our results show that these events are not isolated incidents but rather a complex interplay between anthropogenic emission growth and chronic meteorological stagnation. To understand these dynamics, we used historical fog climatology data from OPLA visibility records, with long-term emission data from the REAS v3.2 inventory. By applying the Anthropogenic Growth Index (AGI), the analysis confirms a significant causal relationship (<i>p</i> &lt; 0.05) between the tripling of regional pollution loads and the sustained decline in local visibility. The study also investigated the vertical thermodynamic profiles using ERA5 reanalysis. The spatial extent of fog and aerosol loading is tracked using the Normalized Difference Snow Index (NDSI) and MODIS aerosol optical depth (AOD). The resulting data highlights a critical atmospheric trapping mechanism that compounds human-induced forcing. This state is defined by persistent temperature inversions between 700 and 900&#xa0;hPa and weak near-surface winds. These stagnant, anti-cyclonic conditions drive relative humidity toward saturation (80–95%), effectively collapsing the surface dew-point depression and preventing the vertical or horizontal dispersal of pollutants. Additionally, an ensemble of CMIP6 models was validated against ERA5-Land reanalysis for winter conditions (2016 to 2024), showing strong agreement in near-surface air temperature (<i>R</i><sup>2</sup> = 0.9) and good correlation for relative humidity (<i>R</i><sup>2</sup> = 0.7), confirming their overall reliability for further analysis. The results indicate that smog over Lahore is linked to large-scale atmospheric processes across the Indo-Gangetic Plain, including inversion conditions and transboundary pollutant transport. Future projections using CMIP6 ensemble multi-models HadGEM3-GC31-MM, EC-Earth3-Veg-LR, CNRM-ESM2-1, MPI-ESM1-2-HR, and CNRM-CM6-1 with the SSP5-8.5 scenario indicate a climatological shift toward increased atmospheric stability for the near-term climate (2025–2049). The analysis forecasts a sustained recurrence of stagnation windows, suggesting that without structural reductions in the anthropogenic baseline identified by the AGI, the region’s meteorology will become increasingly conducive to pollutant retention. These findings highlight that the fog season is evolving into a chronic smog hazard, necessitating adaptive air quality management strategies for urban South Asia.</p>

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Spatiotemporal analysis of climatic and anthropogenic drivers of winter smog in the Indo-Gangetic Plain with a focus on Lahore

  • 期刊论文

  • 发表日期：

    2026年5月15日

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  • Muhammad Zeeshan Ghani,
  • Mujtaba Hassan,
  • Farrukh A. Chishtie,
  • Syeda Saleha Fatim Ali,
  • Syed Waqar Hussain Shah,
  • Ahmad Bilal

摘要

The Indo-Gangetic Plain has emerged as a major global hot spot of wintertime particulate pollution. This is especially evident in Northeastern Pakistan, where cities like Lahore are now recording increasingly extreme smog levels. In this study, we establish the smog formation process over the larger Indo-Gangetic Plain with a focus on Lahore. Our results show that these events are not isolated incidents but rather a complex interplay between anthropogenic emission growth and chronic meteorological stagnation. To understand these dynamics, we used historical fog climatology data from OPLA visibility records, with long-term emission data from the REAS v3.2 inventory. By applying the Anthropogenic Growth Index (AGI), the analysis confirms a significant causal relationship (p < 0.05) between the tripling of regional pollution loads and the sustained decline in local visibility. The study also investigated the vertical thermodynamic profiles using ERA5 reanalysis. The spatial extent of fog and aerosol loading is tracked using the Normalized Difference Snow Index (NDSI) and MODIS aerosol optical depth (AOD). The resulting data highlights a critical atmospheric trapping mechanism that compounds human-induced forcing. This state is defined by persistent temperature inversions between 700 and 900 hPa and weak near-surface winds. These stagnant, anti-cyclonic conditions drive relative humidity toward saturation (80–95%), effectively collapsing the surface dew-point depression and preventing the vertical or horizontal dispersal of pollutants. Additionally, an ensemble of CMIP6 models was validated against ERA5-Land reanalysis for winter conditions (2016 to 2024), showing strong agreement in near-surface air temperature (R2 = 0.9) and good correlation for relative humidity (R2 = 0.7), confirming their overall reliability for further analysis. The results indicate that smog over Lahore is linked to large-scale atmospheric processes across the Indo-Gangetic Plain, including inversion conditions and transboundary pollutant transport. Future projections using CMIP6 ensemble multi-models HadGEM3-GC31-MM, EC-Earth3-Veg-LR, CNRM-ESM2-1, MPI-ESM1-2-HR, and CNRM-CM6-1 with the SSP5-8.5 scenario indicate a climatological shift toward increased atmospheric stability for the near-term climate (2025–2049). The analysis forecasts a sustained recurrence of stagnation windows, suggesting that without structural reductions in the anthropogenic baseline identified by the AGI, the region’s meteorology will become increasingly conducive to pollutant retention. These findings highlight that the fog season is evolving into a chronic smog hazard, necessitating adaptive air quality management strategies for urban South Asia.