Do Aerosols Really Matter Over High Mountain Asia?

Presenter: Chayan Roychoudhury1
Co-Author(s): Cenlin He , Rajesh Kumar, Manish Srivastava , John M. McKinnon
Advisor(s): Dr. Avelino F. Arellano
1Department of Hydrology and Atmospheric Sciences, University of Arizona

Panapto Presentation Video
Oral Session 3: Aerosols, Isotopes, and Soils

As one of the important hydrological sources over Asia, the high mountain Asia (HMA) glacier region is significantly affected in spring by the deposition of light-absorbing particles (LAPs viz. black carbon (BC) and dust) and its consequent radiative effects. In this study, black carbon and dust emission and deposition over the region has been simulated for the recent decade using two model configurations of the Weather Research and Forecasting (WRF-Chem): i.e., 1) full chemistry with aerosol feedback, and 2) regionally tagged tracer transport without aerosol feedback. A multivariate analysis using linear/non-linear regression techniques is then performed across simulated chemistry, aerosol, and hydro-meteorological variables, along with available satellite data products and ERA5/CAMS EAC4 reanalysis to a) explore their multiple associations with observed snow cover and albedo over HMA, and b) evaluate the impact of LAPs from nearby sources on the regional environment. Our results show that the regions largely contributing to BC modeled surface abundance are India, Nepal, and Pakistan (average contribution of 45%) for the Himalayas while India and China for the Tibetan Plateau (25%), where snow cover appears to be highly variable (average standard deviation of 30%). Anthropogenic BC largely dominates more than fire BC across all months. However, based on multiple regression analysis, we also find that the top five variables mostly associated to the changes in snow cover and albedo (from highest to lowest relative importance) are skin temperature, sensible heat flux, mean sea level pressure, total aerosol optical depth (AOD), and medium/high cloud cover - with dust AOD more than BC AOD. Combined feedbacks of chemistry and aerosols in terms of average differences between the two model simulations are evident, particularly on surface temperature (average difference of 0.2%), moisture (3%), and horizontal winds (25%). These feedbacks point towards the need for more observational data constraints in disentangling the impacts of aerosols and chemistry over the Himalayan cryosphere.

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