Hindu Kush Region, by Month, 2013

MAP 5.4 Sources of Black Carbon Deposition in the Himalaya, Karakoram, and Hindu Kush Region, by Month, 2013

Jan

Apr

Jul

Oct Anthropogenic Biomass burning Boundary

0.05 0.15 0.25 0.35 0.45 0.55 0.65 0.75 0.85 0.95

Source: original map created for this publication, based on publicly available climate data sets.

part of the region, including strong impacts in the HKHK regions that peak during the summer monsoon in July. Results suggest that sources of BC outside of South Asia are responsible for a significant fraction of BC deposition in these regions, likely from the long-range transport of BC in the free troposphere that deposits to the mountains of the HKHK region. These results are also consistent with the global modeling results of Kopacz et al. (2011), who find that biomass burning in Africa and fossil fuel combustion in the Middle East can contribute significantly to the BC reaching the Himalayas and the Tibetan plateau.

Industrial and fuel processes are significant sources of BC in the region. Map 5.5 shows the fraction of in-domain anthropogenic (not total) BC deposition from each of the four major anthropogenic sources included in the BC study: industry (including brick kilns), diesel fuel, residential solid fuels, and open burning. These results may not be meaningful near the boundaries of the simulation, where boundary condition BC dominates the quantity of deposition. In the HKHK region, as shown, industry and solid fuel are important in-domain anthropogenic sources, with industry contributing between 31 and 41 percent (minimum of 8 milligrams per day in July, maximum of 46.4 milligrams per day in April) and solid fuel contributing 14–28 percent (minimum of 3.5 milligrams per day in July, maximum of 31.4 milligrams per day in January). Diesel fuel accounts for 7–10 percent of the HKHK BC deposition in January (8.1 milligrams per day), April (10.0 milligrams per day), and October (8.0 milligrams per day), but accounts for 18 percent in July (4.7 milligrams per day).

The BC study also estimates the fraction of in-domain anthropogenic deposition of BC that is due to anthropogenic sources in the six countries studied for each season. As expected, each country has a strong influence on anthropogenic BC deposition within its own jurisdiction, but there is also significant cross-boundary transport of BC in South Asia. For the HKHK region, Bangladesh and Myanmar generally have a negligible impact on cross-boundary BC, while China, India, Nepal, and Pakistan have noticeable contributions. The relative importance of the different nations also varies by season, with China and Pakistan contributing more in-domain anthropogenic deposition in July, while India’s contribution peaks in October and January. However, as in-domain anthropogenic sources account for only 13–62 percent of the total BC deposition in this region, the relative contribution of each nation is generally well below 50 percent.

Overall, under a moderate ENSO year, sources outside the South Asian modeling domain have a similar impact on total BC deposition in the HKHK region (35–87 percent, varying by month) as South Asian anthropogenic sources (13–62 percent), with the boundary contribution peaking in July. The in-domain anthropogenic contribution is from industry (primarily brick kilns) and residential burning of solid fuel, which, when combined, account for 45–66 percent of the in-domain anthropogenic BC deposition in the HKHK region, with on-road diesel fuels making a smaller contribution (7–18 percent, peaking in July) and open burning accounting for less than 3 percent in all seasons. Other sources of BC from anthropogenic combustion (waste burning) were not explicitly tracked but account for the remaining fraction of in-domain emissions.