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<p>Aerosols play a critical role in modulating regional climate by influencing radiative forcing. Therefore, this study analysed the seasonal variabilities and long-term trends in aerosol optical properties (AOPs) and their direct radiative effects (ADRF) over Northwest India from 2005 to 2024 using multiple datasets (MERRA-2, OMI). The observed mean of surface albedo (SA), single scattering albedo (SSA), scattering aerosol optical thickness (AOT), and extinction AOT were 0.217 ± 0.008, 0.960 ± 0.008, 0.378 ± 0.099, and 0.345 ± 0.096, respectively, over Northwest India. The spatial distribution revealed that the Aravalli region (AR) exhibited the highest single scattering albedo (SSA), scattering optical thickness (AOT), and extinction AOT, as well as the lowest surface albedo (SA). Meanwhile, urban areas (Western-Indian-Gangetic plains) showed the opposite pattern (lowest) of AOP variation in Northwest India due to the influence of dust aerosols. Shortwave direct radiative forcing (SWDRF) varies from − 11.16 to -3.27&#xa0;W/m² at the top of the atmosphere (TOA), -37.84 to -12.72&#xa0;W/m² at the surface (SUR), and 7.97 to 26.87&#xa0;W/m² at the atmosphere (ATM). In comparison, longwave direct radiative forcing (LWDRF) ranged from − 2.59 to -0.08&#xa0;W/m² at TOA, 0.76 to 8.37&#xa0;W/m² at SUR, and − 10.96 to -0.93&#xa0;W/m² at ATM. The percentage change revealed a 1.28% increase in SA, a 0.15% decrease in SSA, and modest increases in scattering AOT (2.45%) and extinction AOT (1.99%), suggesting enhanced aerosol loading with a subtle shift toward greater absorption. SWDRF at the TOA increased by 1.33%, while at the SUR, it decreased by 1.84%, resulting in a 3.28% reduction at the ATM level. LWDRF showed a significant decrease of 17.47% at TOA, 3.82% at SUR, and 6.53% at ATM. This study highlights the dual role of aerosols in climate interactions, emphasizing aerosol-driven surface cooling and atmospheric heating. The findings provide a robust framework for future research on aerosol-climate dynamics and inform policies aimed at mitigating the impacts of aerosols on climate and public health.</p>

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Assessment of Aerosol Optical Properties and Dual Nature of Aerosol-Induced Radiative Forcing for Shortwave and Longwave over Northwest India

  • 期刊论文

  • 发表日期：

    2025年10月23日

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  • Prity S. Pippal,
  • Rajesh Kumar,
  • Ramesh Kumar,
  • Atar Singh

摘要

Aerosols play a critical role in modulating regional climate by influencing radiative forcing. Therefore, this study analysed the seasonal variabilities and long-term trends in aerosol optical properties (AOPs) and their direct radiative effects (ADRF) over Northwest India from 2005 to 2024 using multiple datasets (MERRA-2, OMI). The observed mean of surface albedo (SA), single scattering albedo (SSA), scattering aerosol optical thickness (AOT), and extinction AOT were 0.217 ± 0.008, 0.960 ± 0.008, 0.378 ± 0.099, and 0.345 ± 0.096, respectively, over Northwest India. The spatial distribution revealed that the Aravalli region (AR) exhibited the highest single scattering albedo (SSA), scattering optical thickness (AOT), and extinction AOT, as well as the lowest surface albedo (SA). Meanwhile, urban areas (Western-Indian-Gangetic plains) showed the opposite pattern (lowest) of AOP variation in Northwest India due to the influence of dust aerosols. Shortwave direct radiative forcing (SWDRF) varies from − 11.16 to -3.27 W/m² at the top of the atmosphere (TOA), -37.84 to -12.72 W/m² at the surface (SUR), and 7.97 to 26.87 W/m² at the atmosphere (ATM). In comparison, longwave direct radiative forcing (LWDRF) ranged from − 2.59 to -0.08 W/m² at TOA, 0.76 to 8.37 W/m² at SUR, and − 10.96 to -0.93 W/m² at ATM. The percentage change revealed a 1.28% increase in SA, a 0.15% decrease in SSA, and modest increases in scattering AOT (2.45%) and extinction AOT (1.99%), suggesting enhanced aerosol loading with a subtle shift toward greater absorption. SWDRF at the TOA increased by 1.33%, while at the SUR, it decreased by 1.84%, resulting in a 3.28% reduction at the ATM level. LWDRF showed a significant decrease of 17.47% at TOA, 3.82% at SUR, and 6.53% at ATM. This study highlights the dual role of aerosols in climate interactions, emphasizing aerosol-driven surface cooling and atmospheric heating. The findings provide a robust framework for future research on aerosol-climate dynamics and inform policies aimed at mitigating the impacts of aerosols on climate and public health.