[A-AS05] 大気化学

[AAS05-09] ニーオルスンにおける黒色炭素粒子の湿性沈着に関する研究

*森 樹大¹、近藤 豊²、大畑 祥^3,4、東 久美子^2,5、福田 かおり²、小川 佳美²、茂木 信宏⁶、吉田 淳⁶、小池 真⁶、Sinha Puna⁷、大島 長⁸、松井 仁志⁹、當房 豊^2,5、矢吹 正教¹⁰、Aas Wenche¹¹ (1.東京理科大学、2.国立極地研究所、3.名古屋大学宇宙地球環境研究所、4.名古屋大学高等研究院、5.総合研究大学院大学、6.東京大学大学院、7.Department of Earth and Space Sciences, Indian Institute of Space Science and Technology、8.気象研究所、9.名古屋大学大学院、10.京都大学生存圏研究所、11.Norwegian Institute for Air Research)

キーワード：ブラックカーボン、湿性沈着、北極、季節変化、レーザー誘起白熱法

Black carbon (BC) aerosol deposited in and onto Arctic snow increases the snow’s absorption of solar radiation and accelerates snowmelt. Concentrations of BC in the Arctic atmosphere and snow are controlled by wet deposition; however, details of this process are poorly understood owing to the scarcity of time-resolved measurements of BC in hydrometeors. We measured mass concentrations of BC in hydrometeors (C_MBC) and in air (M_BC) with 16% and 15% accuracies, respectively, at Ny-Ålesund, Svalbard during 2012–2019. Median monthly M_BC and C_MBC values showed similar seasonal variations, being high in winter-spring and low in summer. Median monthly BC wet deposition mass flux (F_MBC) was highest in winter and lowest in summer, associated with seasonal patterns of C_MBC and precipitation. Seasonally averaged BC size distributions in hydrometeors were similar except summer. Measurements of BC in air and hydrometeors in spring 2017 showed a size-independent removal efficiency, showing efficient activation of BC-containing particles into cloud droplets. These parameters observed at Ny-Ålesund were compared with those observed at Barrow, Alaska, during 2013–2017. The near surface M_BC at Ny-Ålesund and Barrow had similar seasonal patterns; however, they differed for C_MBC and F_MBC. In summer, C_MBC was low at Ny-Ålesund but moderate at Barrow, likely reflecting differences in M_BC in the lower troposphere. Seasonally averaged BC size distributions in hydrometeors were similar at both sites, suggesting similar BC size distributions in the Arctic lower troposphere, on average. Coating of BC particles at lower latitudes likely influence the BC size distributions in the Arctic.