Journal Article
Atmospheric Chemistry and Physics, vol. 19, iss. 10, pp. 7105-7128, 2019
Authors
Chandan Sarangi, Yun Qian, Karl Rittger, Kathryn J. Bormann, Ying Liu, Hailong Wang, Hui Wan, Guangxing Lin, Thomas H. Painter
Abstract
Abstract. Light-absorbing particles (LAPs), mainly dust and black carbon, can
significantly impact snowmelt and regional water availability over high-mountain Asia (HMA). In this study, for the first time, online aerosol–snow
interactions are enabled and a fully coupled chemistry Weather Research and
Forecasting (WRF-Chem) regional model is used to simulate LAP-induced
radiative forcing on snow surfaces in HMA at relatively high spatial
resolution (12 km, WRF-HR) compared with previous studies. Simulated macro- and
microphysical properties of the snowpack and LAP-induced snow darkening are
evaluated against new spatially and temporally complete datasets of snow-covered area, grain size, and impurity-induced albedo reduction over HMA.
A WRF-Chem quasi-global simulation with the same configuration as WRF-HR but
a coarser spatial resolution (1∘, WRF-CR) is also used to illustrate
the impact of spatial resolution on simulations of snow properties and
aerosol distribution over HMA. Due to a more realistic representation of
terrain slopes over HMA, the higher-resolution model (WRF-HR) shows
significantly better performance in simulating snow area cover, duration of
snow cover, snow albedo and snow grain size over HMA, as well as an
evidently better atmospheric aerosol loading and mean LAP concentration in
snow. However, the differences in albedo reduction from model and satellite
retrievals is large during winter due to associated overestimation in
simulated snow fraction. It is noteworthy that Himalayan snow cover has
high magnitudes of LAP-induced snow albedo reduction (4 %–8 %) in
pre-monsoon seasons (both from WRF-HR and satellite estimates), which induces a
snow-mediated radiative forcing of ∼30–50 W m−2. As a
result, the Himalayas (specifically the western Himalayas) hold the most vulnerable
glaciers and mountain snowpack to the LAP-induced snow darkening effect
within HMA. In summary, coarse spatial resolution and absence of
snow–aerosol interactions over the Himalayan cryosphere will result in
significant underestimation of aerosol effects on snow melting and regional
hydroclimate.
