[A-AS07] Atmospheric Chemistry

[AAS07-06] Controlling factors of temporal variations of black carbon concentration over the Arctic region

Kyoma Yahara¹, Tomoki Nishiyama¹, *Kazuyo Yamaji¹, Fumikazu Taketani², Masayuki Takigawa², Yugo Kanaya² (1.Kobe University, 2.Japan Agency for Marine-Earth Science and Technology)

Keywords:Black carbon, Air quality model, WRF/CMAQ, Arctic

Black carbon (BC) emitted into the atmosphere from fuel combustions and biomass burning efficiently absorbs solar radiation and heats the atmosphere directly; therefore, it is an important short-lived climate forcing factor (SLCF). Accumulated BC over snow and ice promotes their melting. Consequently, BC is a major heating driver especially over the Arctic region. Observed surface BC concentrations at three Arctic monitoring stations, Alert, Barrow, and Ny-Alesund of the Arctic region indicated a typical seasonal variation such as increasing from winter to early spring and decreasing during the warmer season with the large interannual variabilities. Meanwhile, the BC enhancements of a short-span with a few weeks to one month were found in the summer season. Observed annual averaged BC concentrations in 2015 were the highest in 2014-2018, while the concentrations were precipitously decreased in 2016. The interannual variabilities of BC concentrations might be caused by differences in the air-mass transport patterns from the source regions and the occurrence of forest fires in Siberia and Alaska over the years. To investigate the primary factors causing the differences between the higher BC year and the lower BC year, hemispheric scale air quality simulation has been performed for 2015 and 2016 by WRF/CMAQ model using HTAPv2.2 and GFASv1.2 emission inventories. It was found that the model could reasonably capture the concentration levels and seasonal patterns of observed BC at Alert, Barrow, and Ny-Alesund in 2015. Furthermore, compared with onboard observations by the research vessel Mirai promoted as part of the Arctic Challenge for Sustainability project (ArCS), the timing of the inflow of polluted air masses from the Asian continent was relatively well reproduced by the model simulations, confirming the BC transport from Asia through the western North Pacific to higher latitudes. CMAQ simulations indicated that biomass burning in the Alaska and Siberia areas promoted BC increasing in the summer season over the Arctic region. We will discuss the primary factors for the higher BC concentrations in the Arctic region in 2015 through a comparative analysis with the 2016 case under the lower BC condition.