Optical Properties of Fine Mode Aerosols over High-Altitude Himalayan Glacier Regions

Duringthe summer and winter periods of 2019-2020, we conductedsampling of fine mode ambient aerosols in the western Himalayan glacialregion (WHR; Thajiwas glacier, 2799 m asl), central Himalayan glacialregion (CHR; Gomukh glacier, 3415 m asl), and eastern Himalayan glacialregion (EHR; Zemu glacier, 2700 m asl). We evaluated the aerosol opticalproperties, which included the mass absorption coefficient, mass absorptionefficiency, mass scattering efficiency, absorption angstrom exponent,single scattering albedo, as well as their simple radiative forcingefficiencies. We observed the highest absorption in the near ultraviolet-visiblewavelength range (200-400 nm), with CHR showing the highestabsorption compared to the other two sites, WHR and EHR, respectively.Across the wavelength range of 200-1100 nm, the overall contributionof black carbon to light attenuation was greater than that of browncarbon. However, brown carbon dominated the absorption in the nearUV-visible wavelengths, providing evidence of its non-trivialpresence over the Himalayan region. Additionally, we observed a positiveradiative forcing (W/g), which leads to net warming at these sites.The findings of this ground-based study contribute to our understandingof the light-absorbing nature of carbonaceous aerosols and their impacton the Himalayan glacier regions.