Abstract. We collected surface snow samples from three different glaciers –
Yala, Thana, and Sachin – in the central and western Himalayas to understand
the spatial variability and radiative impacts of light-absorbing particles.
The Yala and Thana glaciers in Nepal and Bhutan, respectively, were selected
to represent the central Himalayas. The Sachin glacier in Pakistan was
selected to represent the western Himalayas. The samples were collected
during the pre- and post-monsoon seasons of the year 2016. The samples were
analyzed for black carbon (BC) and water-insoluble organic carbon (OC)
through the thermal optical method. The average mass concentrations (BC 2381 ng g−1; OC 3896 ng g−1; dust 101 µg g−1) in the
western Himalayas (Sachin glacier) were quite high compared to the mass
concentrations (BC 358 ng g−1, OC 904 ng g−1, dust 22 µg g−1) in the central Himalayas (Yala glacier). The difference in mass
concentration may be due to the difference in elevation, snow age, local
pollution sources, and meteorological conditions. BC in
surface snow was also estimated through Weather
Research and Forecasting (WRF) model coupled with Chemistry (WRF-Chem) simulations at the three
glacier sites during the sampling periods. Simulations reasonably capture
the spatial and seasonal patterns of the observed BC in snow but with a
relatively smaller magnitude. Absolute snow albedo was estimated through the
Snow, Ice, and Aerosol Radiative (SNICAR) model. The absolute snow albedo
reduction ranged from 0.48 % (Thana glacier during September) to 24 % (Sachin glacier during May) due to BC and 0.13 % (Yala glacier
during September) to 5 % (Sachin glacier during May) due to dust. The
instantaneous radiative forcing due to BC and dust was estimated in the
range of 0 to 96.48 and 0 to 25 W m−2, respectively. The
lowest and highest albedo reduction and radiative forcing were observed in
central and western Himalayan glaciers, respectively. The potential source
regions of the deposited pollutants were inferred using WRF-Chem
tagged-tracer simulations. Selected glaciers in the western Himalayas were
mostly affected by long-range transport from the Middle East and central
Asia; however, the central Himalayan glaciers were mainly affected by local
and south Asia emissions (from Nepal, India, and China) especially during
the pre-monsoon season. Overall, south Asia and west Asia were the main
contributing source regions of pollutants.