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<p>This research investigates the seasonal and interannual variability of Aerosol Optical Depth (AOD) and Ångström Exponent (AE) over Assam, India, using MODIS data (2012–2021) to characterize regional aerosol loading and type. The western region exhibited the highest mean AOD (0.55 ± 0.17), followed by the central (0.45 ± 0.15) and eastern (0.41 ± 0.16) regions, with peak values during the pre-monsoon season (0.68 ± 0.11). Fine-mode aerosols dominated in winter (AE: 1.41 ± 0.18) and post-monsoon (AE: 1.39 ± 0.20), while mixed aerosol conditions prevailed during pre-monsoon (AE: 1.19 ± 0.24) and monsoon (AE: 1.04 ± 0.38). HYSPLIT analysis indicated potential long-range transport influences, alongside local fire activity. Hierarchical clustering revealed distinct seasonal and regional aerosol regimes. Winter shows moderate AOD but high AE, indicating dominance of fine-mode aerosols likely associated with urban and combustion sources. The pre-monsoon season exhibited the high aerosol diversity, likely influenced by dust transport and anthropogenic pollution. The monsoon season exhibits lower aerosol loading with a mixture of particle types, whereas the post-monsoon season is dominated by fine-mode aerosols from combustion and urban sources, occasionally punctuated by intensity pollution events. These findings improve understanding of aerosol climatology over Assam, India, with implications for air quality and climate assessments.</p>

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Seasonal aerosol characteristics and their classification over Assam, India

  • 期刊论文

  • 发表日期：

    2026年6月23日

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  • Dhiman Barua,
  • Hirakjyoti Goswami

摘要

This research investigates the seasonal and interannual variability of Aerosol Optical Depth (AOD) and Ångström Exponent (AE) over Assam, India, using MODIS data (2012–2021) to characterize regional aerosol loading and type. The western region exhibited the highest mean AOD (0.55 ± 0.17), followed by the central (0.45 ± 0.15) and eastern (0.41 ± 0.16) regions, with peak values during the pre-monsoon season (0.68 ± 0.11). Fine-mode aerosols dominated in winter (AE: 1.41 ± 0.18) and post-monsoon (AE: 1.39 ± 0.20), while mixed aerosol conditions prevailed during pre-monsoon (AE: 1.19 ± 0.24) and monsoon (AE: 1.04 ± 0.38). HYSPLIT analysis indicated potential long-range transport influences, alongside local fire activity. Hierarchical clustering revealed distinct seasonal and regional aerosol regimes. Winter shows moderate AOD but high AE, indicating dominance of fine-mode aerosols likely associated with urban and combustion sources. The pre-monsoon season exhibited the high aerosol diversity, likely influenced by dust transport and anthropogenic pollution. The monsoon season exhibits lower aerosol loading with a mixture of particle types, whereas the post-monsoon season is dominated by fine-mode aerosols from combustion and urban sources, occasionally punctuated by intensity pollution events. These findings improve understanding of aerosol climatology over Assam, India, with implications for air quality and climate assessments.