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2004-2007年に行ったエアロゾル重点観測中に,昭和基地でヘイズ現象が観測された.ヘイズ現象時は風が比較的弱く,降雪・地吹雪は観測されず,冬～ 春にヘイズが出現していた.「南極ヘイズ」時には,バックグラウンド状態と比べてエアロゾル数濃度が1-2桁ほど増加していた.エアロゾル成分のバルク分析から,ヘイズ現象中のエアロゾル主成分は海塩成分(e.g., Na^+, Cl^->)と判明した.流跡線解析とNAAPSモデルから,南アメリカやアフリカ南部でのバイオマス燃焼の影響を受けた空気塊が,南大洋上の低気圧活動に伴って昭和基地まで輸送されていることが示唆された.中低緯度域から極域方向への空気塊流入と,輸送中の海塩粒子の発生と混合とにより,「南極ヘイズ」が出現しているのだろう.バックグラウンド時とヘイズ時のO_3 濃度の差は,冬よりも極夜明け後の春に大きくなる傾向が確認された.不均一反応により海塩粒子から高反応性ハロゲン化合物が放出されることがあるため,極夜明け後の南極沿岸域でのヘイズ現象は,地上O_3 消失現象にも密接に関連している可能性がある., During our aerosol measurement program at Syowa Station, Antarctica in 2004-2007, some low visibility (haze) phenomena were observed under conditions with weak wind and without drifting snow and fog in winter-spring. In the "Antarctic haze" phenomenon, the number concentration of aerosol particles and black carbon concentration increased by one-two orders higher relative to background conditions at Syowa Station, while surface O_3 concentration simultaneously dropped especially after polar sunrise. Major aerosol constituents in the haze phenomenon were sea-salts (e.g., Na^+ and Cl^-). From the trajectory analysis and NAAPS model, the plumes from biomass burning in South America and southern Africa were transported to Syowa Station, Antarctic coast, during eastward (occasionally westward) approach of cyclones in the Southern Ocean. Thus, poleward flow of the plume from mid-latitudes and injection of sea-salt particles during the transport may lead to the Antarctic haze phenomenon at Syowa Station. The difference of O_3 concentration between the background and the haze conditions tended to be larger in spring (polar sunrise) relative to that in winter. Because enhancement of sea-salt particles can play an important role as an additional source of reactive halogen species, the haze episodes might make a significant contribution to surface O_3 depletion during the polar sunrise on the Antarctic coast.

2004年2月～ 2005年1月にかけて昭和基地で直径5-168 nmの粒径分布を連続観測した.粒径分布は,冬に1～ 2のモードから成り,濃度の高いモードは50 nm以上であることが多く,春～ 夏や秋には2～ 3のモードから成り,濃度の高いモードは20-80 nm付近にあることが多かった.50 nm以上に谷を持つ粒径分布の出現頻度は,開水面が昭和基地に近い夏～ 秋に多かった.一山のみの粒径分布は冬と初夏に多くなり,冬には幅が広く,初夏には幅の狭い分布を示した.初夏から初秋にかけて,10-20 nm付近の核形成モード粒子の濃度が高くなることがあった.11月下旬には,カタバ風の弱くなる午後に核形成モード粒子の濃度が高くなる事例を数日にわたり観測した., Number-size distributions (5-168 nm in diameter) of atmospheric aerosol particles were measured at Syowa Station, Antarctica from February 2004 to January 2005. Size distributions in winter consisted of 1 to 2 modes larger than 50 nm in diameter, whereas 2 to 3 modes contributed to the size distributions in October to March with mode diameters between 20 and 80 nm. Size distribution with a valley at around 50 nm was often observed in summer to fall when the open ocean was located near Syowa Station. From September to March, concentration of ultra fine particles (

南極海における大気エアロゾル粒子の粒径分布やイオン成分濃度,先駆ガス濃度の時空間分布を調べるために,「白鳳丸」や「タンガロア」,「海鷹丸」による船上観測をおこなった.海況の穏やかな南極海での観測では,直径0.1 μm以上の既存エアロゾル粒子数濃度が著しく低い条件下で,高濃度の核生成モード粒子(直径, To investigate spatial and temporal variation of number-size distribution of atmospheric aerosol particles in the Antarctic Ocean, atmospheric observations were conducted on research vessels: Hakuho-maru, Tangaroa, and Umitaka-maru. Concentrations of ionic constituents in aerosols and precursor gases (SO_2 and NH_3) were also measured during the cruises. Concentrations of nucleation mode particles (

第46-47次日本南極地域観測隊で,超微小粒子の粒径分布とその揮発特性の連続観測を実施した.夏季には超微小粒子のほとんどは揮発性粒子で,硫酸,メタンスルホン酸,硫酸塩で構成されていた.夏には超微小粒子域の非揮発性粒子の割合は20% だったが,冬季には90% を超すこともあった.冬季の超微小粒子のほとんどは海塩粒子であり,海氷上で組成分別をした海塩粒子も含まれていた.南極大陸内陸部上空から昭和基地(沿岸部)に空気塊が輸送される時には,冬季にも揮発性粒子の割合が減少していた., The Size distribution and volatility of ultrafine aerosol particles were measured at Syowa Station during the 46-47 Japanese Antarctic Research Expeditions. During the summer, most of the ultrafine particles were volatile particles, which were composed of H_2SO_4, CH_3SO_3H and sulfates bi-sulfates. The abundance of non-volatile particles was ～ 20% during the summer, increasing to>90% in winter-spring. Non-volatile particles in winter were dominantly sea-salt particles. Some ultrafine sea-salt particles might be released from sea-ice. When air mass was transported from the free troposphere over the Antarctic continent, the abundance of non-volatile particles dropped to

第46次日本南極地域観測隊において,係留気球を用いたエアロゾル鉛直分布観測を南極昭和基地で実施した.CN数濃度の季節変化は夏に極大を示す傾向があったが,微小(D_p>0.3 μm)～ 粗大(D_p>2.0 μm)粒子数濃度は夏季に低く,冬季に高くなっていた.CN濃度変化の幅は,地上付近では30-2200 cm^ の範囲で変化していたが,自由対流圏(>1500 m)での変化幅は7-7250 cm^ となっていた.夏季の自由対流圏下部では,新粒子生成による高CN数濃度が観測された.地上での新粒子生成イベントが確認されるよりも高い頻度で,南極域の自由対流圏下部において新粒子生成が起きていることが示唆される.また,個別粒子分析の結果から,冬季には,海氷上で起こる組成分別過程によりMgが濃縮されている海塩粒子と,NO_3^ やSO_4^ により変質した粒子が多かった.海塩の組成分別過程によるMg濃縮海塩粒子とその変質過程が,冬季のエアロゾル粒子の吸湿特性に大きな影響を及ぼしていることが示唆される.Hara et al.(2010a)で報告されているヘイズ現象は,境界層だけではなく,自由対流圏でも観測されることがあった., Tethered balloon-borne aerosol measurements were carried out at Syowa Station, Antarctica during the 46th Japanese Antarctic Research Expedition. CN concentration had a maximum in the summer, whereas the number concentrations of fine particles (D_p>0.3 μm) and coarse particles (D_p>2.0 μm) increased during the winter-spring. The range of CN concentration was 30-2200 cm^ near the surface (surface-500 m) and 7-7250 cm^ in the lower free troposphere (>1500 m). During the austral summer, higher CN concentration was often observed in the lower free troposphere. Frequent appearance of higher CN concentration in the free troposphere relative to the surface measurements strongly suggests that new particle formation in the Antarctic regions occurs in the lower free troposphere. Single particle analysis indicated that most of the aerosol particles during the winter were composed of Mg-enriched sea-salt particles originated from sea-salt fractionation on the sea-ice and their modified particles by NO_3^ and SO_4^. This suggests that sea-salt fractionation on sea-ice and modification of sea-salt particles were affected greatly by aerosol hygroscopicity during the winter. Antarctic haze layer was observed not only in the boundary layer but also in the lower free troposphere.