Abstract:
Aerosol optical and radiative properties over the Leh Ladakh, located in the climate sensitive Hindu Kush
Himalayan region are examined using one year measurements from a newly installed sky radiometer from July
2023 to June 2024. Columnar aerosol optical depth (AOD), at 500 nm exhibits a distinct seasonal variation
with peak during spring (0.104 ± 0.041) and minimum in autumn (0.077 ± 0.031), while Extinction Angstrom
Exponent (EAE) is found to be maximum in winter (1.041 ± 0.205) and minimum (0.658 ± 0.225) in spring.
The highest EAE in winter is complemented with the highest AOD_Fine-mode (0.071 ± 0.034) among the
seasons which may be associated with the combustion of firewood, charcoal, kerosene or other fuels used to
burn to bear the cold winter months, when temperature varied between −15 and −25 ◦C. Seasonal variation
of Single Scattering Albedo (SSA) at 500 nm varied from 0.905 ± 0.055 (winter) to 0.942 ± 0.061 (summer),
while the lowest value of SSA during winter is complemented with more absorbing aerosols during winter
season. The dominance of fine mode aerosols during the winter seasons is also complemented by the bi-modal
volume size distribution. However, the station is experiencing a negligible contribution of dust-aerosols (1%),
followed by 18% mixed aerosols and 16% non-absorbing aerosols. The current observing site is dominated
by absorbing aerosols which contributed by highly absorbing (49%), moderately absorbing (9%) and slightly
absorbing (6%) during the one year of study period. The absorbing aerosols are characterized by high values
of AOD_Fine-mode (0.061 ± 0.028), imaginary refractive-index (0.014 ± 0.009), EAE (0.932 ± 0.240) and low
value of SSA_Total (0.872 ± 0.070). On the other hand, the non-absorbing aerosols are characterized by high
values of AOD_Total (0.088 ± 0.040), SSA_Total (0.991 ± 0.016), SSA_Coarse-mode (0.978 ± 0.038), and low
value of imaginary refractive-index (∼0.001). The estimated aerosol radiative forcing (ARF) reveals the high
heating rates during spring (0.09 K day−1) among the seasons, while the heating rate is found to be highest
by absorbing aerosols (0.08 K day−1) among the aerosol types.
