Tracing the sources of black carbon deposition over the glaciers in High Mountain Asia: A tagged-tracer approach using WRF-Chem

As an important hydrological source in Asia, glaciers in High Mountain Asia (HMA) have long been a target of light-absorbing particles (LAPs, viz. black/brown carbon (BC/BrC), and dust) from pollution hotspots in major Asian regions that are instrumental in accelerated snowmelt and radiative effects on the climate. For this study, we simulate the deposition of carbonaceous and dust aerosols using the Weather Research and Forecasting coupled with chemistry (WRF-Chem) model over HMA for the last two decades by assimilating MODIS aerosol optical depth (AOD) and MOPITT carbon monoxide (CO) and using a tagged tracer approach to model BC abundance and deposition from 10 Asian regions. Based on previous results from ECMWF datasets through relative importance analysis, carbonaceous aerosols dominate aerosol-meteorology interactions in their importance to snow cover variability during the late snowmelt season (June-July), following which we use a similar approach in estimating the relative importance of these 10 tagged regions to observed MODIS snow cover fraction (SCF) in their role in BC emissions and deposition over the glaciers in HMA. Our results show that BC deposition in the Himalayan glaciers can be largely attributed to India and Pakistan while those in the Tibetan Plateau to India and China. Differences between anthropogenic and biomass burning BC are also observed. These results are an important assessment of the source attribution of anthropogenic activities to glacial melt from rapidly developing countries surrounding HMA and will aid in relevant climate-related policies in the region.