Preliminary report of "Arctic Airborne Measurement Program 2002" (AAMP02)

The Arctic Airborne Measurement Program 2002(AAMP 02) campaign was carried out in March 2002 as one of the sub programs of the project Variations of atmospheric constituents and their climate impact in the Arctic". The main goal of the project was to investigate the transport, transformation and radiative effect of trace gases and aerosols, and their role in the global climate. An instrumented jet plane, Gulfstream II(G-II), was flown from Nagoya, Japan via Barrow, Alaska to Longyearbyen(78°N , 15°E ), Svalbard, crossing the Arctic Ocean in the lower stratospher. Three local flights were made over the Greenland Sea around Svalbard and two profile flights near Barrow. The plane was equipped with CO_2 and ozone analyzers, gas and aerosol sampling systems, aerosol particle counter, nephelometer, absorption photometer, PMS particle probes, sunphotometer, dew point hygrometer and dropsonde system. During the campaign, intensitive surface operations were also conducted at Ny-Ålesund(79°N , 12°E ), Svalbard. Vertical profiles of several trace gases gave information about transport, a new observation by sunphotometer derived an aerosol optical depth in the stratosphere, and another new observation by dropsonde gave information on the polar vortex

ホッキョク コウクウキ カンソク ケイカク (AAMP02) ト ナンキョク ショウワキチ スウェーデン・キルナ オヨビ ニホン サンリク ジョウクウ ニオケル セイソウケン タイキ サイシュ ジッケン ニヨッテ カンソク サレタ タイキ シュヨウ セイブン ノ ジュウリョク ブンリ

成層圏における大気成分の重力分離を調べるため,北極航空機観測計画(AAMP02)において採取した大気試料の酸素・窒素比(δ(O_2 N_2)),窒素と酸素の安定同位体比(δ^N,δ^O),およびアルゴン・窒素比(δ(Ar N_2))を分析した.AAPM02において観測されたスバールバル諸島およびバロー上空の成層圏のδ^N,δ^Oおよびδ(Ar N_2) の関係は質量依存型の同位体分別を示しており,極渦内の成層圏最下部で大気主成分の重力分離が検出可能であることを示唆している.また,δ(O_2 N_2) と二酸化炭素(CO_2)濃度およびその安定炭素同位体比(δ^C)との関係からは,対流圏での高度分布が地表での季節変化の上方伝搬によって形成され,成層圏での高度分布が鉛直方向の空気塊の年代差に加えて,重力分離の影響を受けて形成されていることが示唆された.南極昭和基地上空,スウェーデン・キルナ上空および日本三陸上空において,大気球を用いたクライオジェニックサンプリングによって採取した,中部成層圏大気試料のδ^Nおよびδ^Oの分析から,重力分離は場所によって異なる高度分布を示し,その程度は極渦内で観測が行われたキルナ上空で最も大きいことが明らかとなった.このことから,重力分離の観測は成層圏における空気塊の鉛直輸送に関する情報をもたらす可能性が示唆される.重力分離,空気塊の平均年代および一酸化二窒素(N_2O)濃度の関係から,N_2O > 125 ppbvおよびN_2O O N of N_2, δ^O of O_2 and Ar N_2 ratio (δ(Ar N_2)). The relationship between observed stratospheric δ^N of N_2, δ^O of O_2 and δ(Ar N_2) over the Svalbard Islands and Barrow showed mass-dependent fractionation of atmospheric components in the stratosphere, which suggested that gravitational separation could be observable in the lowermost stratosphere inside the polar vortex. By examining the rates of change in δ(O_2 Nv) and δ^C of CO_2 relative to the CO_2 concentration, such observed correlations were bound to be mainly attributable to upward propagation of their seasonal cycles produced in the troposphere and height-dependent air age as well as gravitational separation in the stratosphere. Air samples collected over Syowa Station, Antarctica, Kiruna, Sweden and Sanriku, Japan using balloon-borne cryogenic air samplers were analyzed for δ^N of Nv and δ^O of O_2. Strength of the gravitational separation was a function of latitude, showing the largest separation inside the polar vortex over Kiruna. It is suggested that information on increase of gravitational separation with height is useful in understanding the vertical transport of air masses in the stratosphere. By comparing the gravitational separations, mean age of air and N_2O concentration at two height intervals with N_2O concentrations > 125 ppb and < 45 ppb, the effect of descending air was found to be more significant over Kiruna than over Syowa Station and Sanriku. The variation in the gravitational separation with height is found to be weaker in the region with N_2O concentrations between 45 and 125 ppb than in other regions, which might suggest that vertical mixing of air occurred in this region

クライオジェニックサンプラー ヲ モチイタ ショウワキチ ジョウクウ ニオケル セイソウケン タイキチュウ ノ オンシツコウカ キタイ カンソク

南極昭和基地において,気球を用いた温室効果気体の観測を実施した.2003年12月26日と2004年1月5日にそれぞれ気球が放球され,高度10 kmから30 kmにおいて,成層圏の大気サンプルを採取することに成功した.大気サンプルを日本に持ち帰った後に,温室効果気体の濃度とその同位体などの分析が行われた.その結果,二酸化炭素の濃度は,高度20 kmより上空においてほぼ一定となり,その平均濃度を1998年1月に実施した気球観測の結果と比較して,およそ9.7 ppmだけ増加していることが明らかになった.二酸化炭素濃度から成層圏大気の平均年代を推定したところ,高度20 kmより上空での平均年代は,5.0±0.2年であった.過去のデータからも平均年代を推定した結果,その値はほぼ一致しており,南極上空の成層圏の平均年代に長期的な変化はみられなかった.N_2Oのアイソトポマー比は12-1月および1998年1月の観測結果の間で高度分布に異なる特徴が見られ,短期的・長期的な輸送過程の変動の影響が示唆された.Balloon-borne cryogenic samplers were launched from Japanese Antarctic Station, Syowa, on December 26, 2003 and January 5, 2004. Stratospheric air samples were successfully collected at 11 different altitudes from 10 to 30 km. After air samples were transported to Japan, they were analyzed for various greenhouse gases and their isotopes. The CO_2 concentration, thus obtained, shows no significant vertical gradient above 20 km. Secular increase of CO_2 concentration was clearly observable in the mid-stratosphere over Syowa station. From the average CO_2 concentrations in 1998 and 2004, the concentration difference was calculated to be 9.7 ppm, which is almost same the tropospheric trend. The average mean age was estimated to be 5.0±0.2 years above 20 km. This value was almost the same as that estimated from the CO_2 concentration data in 1998, 4.9±0.2 years. This result implies that there is no secular change of the mean age in the Antarctic stratosphere during this period. Vertical distributions of N_2O isotopomer ratios showed different characteristics among December, January, and previous observations in January 1998, showing that the short-term and long-term effects of transport processes

ナンボク リョウキョクイキ ニオケル タイキチュウ ノ オンシツ コウカ キタイ ト カンレン キタイ ノ ヘンドウ

南北両極域における温室効果気体の変動を明らかにし,それらの放出源・吸収消滅源の変動に関する知見を得るために,南極・昭和基地および北極・スバールバル諸島ニーオルスンにおいて系統的な温室効果気体及び関連気体観測を開始し,現在も継続している.大気中のCO_2 濃度は,両極域共に明瞭な季節変化を伴いながら,化石燃料消費と森林破壊によるCO_2 の放出を反映して約1.9 ppmv yr^ の割合で増加している.CH_4 濃度にも明瞭な季節変化と不規則な経年変化が見られ,両極域において1999年までの濃度増加と2000年以降の濃度停滞,そして2007年には再び濃度増加が観測された.CH_4 の同位体比観測から,CH_4 濃度の季節変化,経年変化の原因に関する情報が得られた.大気中のO_2 濃度(δ(O_2 N_2))は両極域において,季節変化と化石燃料消費に起因する経年的減少を示した.Atmospheric Potential Oxygen(APO)とCO_2 濃度の増加率から見積もられた,陸上生物圏と海洋によるCO_2 吸収量(2001-2009年の平均)はそれぞれ1.1,2.7 GtC yr^ であった.ニーオルスンで観測されたN_2O濃度の季節変化を3次元化学輸送モデルによる計算結果と比較することにより,N_2O濃度の季節変化振幅は,夏季に成層圏起源のN_2O濃度が低い気塊が地表付近まで流入することによって,拡大している可能性が示唆された.昭和基地におけるCO濃度の連続観測と3次元化学輸送モデルを用いた解析により,2003年2-3月と2007年2月に,オーストラリアでの大規模な林野火災によって発生したCOが昭和基地に達していることが示された.昭和基地における地上オゾン濃度連続観測によって,1988-2008年までの間に計40例以上の地上オゾン破壊現象を観測した.To elucidate temporal variations of greenhouse gases and their related gases in the Arctic and Antarctic regions and to investigate their sources and sinks, systematic measurements of atmospheric CO_2, CH_4CO, N_2O, O_2 and tropospheric O_3 concentrations have been carried out at Syowa Station, Antarctica and Ny-Alesund, Svalbard. The CO_2 concentrations at both polar sites have increased at a rate of about 1.9 ppmv yr^, reflecting fossil fuel combustion and land use change. The CH_4 concentrations also showed clear seasonal cycles superimposed on complex secular trends. The increase rate of the CH_4 concentration varied with time. CH_4 increases were observed until 1999, the concentrations remained steady from 2000 to 2006 and then rapid increases were observed in 2007. Stable isotope data of CH_4 revealed causes of the seasonal cycles and the secular variations of the CH_4 concentrations. The O_2 concentrations (δ(O_2 N_2)) at both polar sites showed prominent seasonal cycles and secular decreasing trends. From analyses of the Atmospheric Potential Oxygen (APO) and CO_2 concentrations, the CO_2 uptake rates by the terrestrial biosphere and the ocean were estimated to be 1.1 and 2.7 GtC yr^, respectively. By comparing the N_2O concentrations observed at Ny-Alesund and numerical model results, it was suggested that the observed seasonal N_2O cycle could be enlarged by intrusion of a stratospheric air mass with low N_2O concentration into the troposphere in summer. With an analysis using a three dimensional chemical-transport model and the CO concentration at Syowa Station, sporadic increases of CO concentration observed in February-March, 2003 and February, 2007 were ascribed to CO release by large-scale forest fires in Australia. Surface ozone depletion events were observed more than 40 times at Syowa Station from 1988 to 2007

Modelling of greenhouse gases and related species in the Arctic environment

Numerical modelling of greenhouse gases (GHGs) has become an integral part for understanding amplitude and variability in their concentrations and sources/sinks, atmospheric transport and climate implication. Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are the three major species studied in the Arctic Green Network of Excellence (GRENE), a programme funded by the Ministry of Education, Culture, Sports, Science and Technology-Japan (MEXT). In addition some of the ozone depleting substances, e.g., methyl chloroform (CH3CCl3), have provided strong constrain on the global mean abundance of hydroxyl (OH) radical and its relative abundance in the northern and southern hemispheres (NH/SH OH ratio; Patra et al., 2014). Being the main destroyer of many of the GHGs (e.g., CH4, hydrofluorocarbons), accurate quantification of OH was needed for estimation of CH4 sink in the troposphere, and thus the sources on the Earth’s surface by inverse modelling (Patra et al., 2016). OH is also contributes to chemical production of CO2, up to ~50% of land/ocean sink. The modellers are also required to verify the accuracy of model transport using tracers of short (e.g., 222Rn with 3.8 days) and long (SF6 with 3200 yrs) lifetimes. For understanding of the carbon cycle science, analyses of oxygen (O2/N2) variability are also conducted. List of chemistry-transport models (CTMs) participating in the Arctic GRENE programme are given Table 1.O08-05, Final Symposium on GRENE-Arctic Climate Change Research Project = GRENE北極気候変動研究事業研究成果報告会 (3-4 March, 2016, National Institute for Japanese Language and Linguistics, Tachikawa, Japan

Development of a new high precision continuous measuring system for atmospheric O2/N2 and Ar/N2 and its application to the observation in Tsukuba, Japan

A high precision continuous measurement system has been developed for analysis of the atmospheric O2/N2 and Ar/N2 ratios based on a mass spectrometry method. Sample and reference air flows through an inlet system and only a miniscule amount of each is transferred to the ion source of the mass spectrometer through thermally insulated thin fused silica capillaries. The measured O2/N2 and Ar/N2 values are experimentally corrected for the effects of pressure imbalance between the sample air and reference air during their introduction into the mass spectrometer, as well as for the influence of CO2 concentration and O2/N2 ratio of the sample air. Standard deviations of the measured O2/N2 and Ar/N2 ratios of standard air are ±3.2 and ±6.5 per meg, respectively, for our normal measurement time of 62 seconds. Our standard air is prepared by drying natural air and then stored in 48-L high-pressure cylinders; its O2/N2 and Ar/N2 ratios are stable to within ±1.1 and ±5.8 per meg, respectively, over a period of 11 months. The CO2/N2 ratio is also simultaneously measured by this system, and converted to CO2 concentration with a precision better than ±0.3 ppm using an experimentally determined relationship. This system has been field tested in Tsukuba, Japan since February 2012. Preliminary results show clear seasonal cycles of atmospheric potential oxygen (APO=O2 +1.1×CO2), as well as of Ar/N2. If we ignore the fossil fuel influence, then that part the seasonal APO cycle driven by the air–sea heat flux accounts for 23% of the observed seasonal APO cycle, as estimated from the seasonal cycle of Ar/N2; any residuals are attributed to ocean biology and ventilation

High Precision Measurements of the Atmospheric O_2/N_2 Ratio on a Mass Spectrometer

科研費報告書収録論文(課題番号:13440137・基盤研究(B)(2) ・H13～H15/研究代表者:青木, 周司/大気中の酸素濃度と二酸化炭素の炭素同位体を用いた地球規模の炭素循環の解明

Gravitational separation of major atmospheric components observed in the stratosphere over Syowa Station, Antarctica, Kiruna, Sweden and Sanriku, Japan.

To investigate the gravitational separation of atmospheric components in the stratosphere, air samples collected using an aircraft during the Arctic Airborne Measurement Program 2002 (AAMP02) were analyzed for the O_2 N_2 ratios (δ(O_2 N_2)), δ^N of N_2, δ^O of O_2 and Ar N_2 ratio (δ(Ar N_2)). The relationship between observed stratospheric δ^N of N_2, δ^O of O_2 and δ(Ar N_2) over the Svalbard Islands and Barrow showed mass-dependent fractionation of atmospheric components in the stratosphere, which suggested that gravitational separation could be observable in the lowermost stratosphere inside the polar vortex. By examining the rates of change in δ(O_2 Nv) and δ^C of CO_2 relative to the CO_2 concentration, such observed correlations were bound to be mainly attributable to upward propagation of their seasonal cycles produced in the troposphere and height-dependent air age as well as gravitational separation in the stratosphere. Air samples collected over Syowa Station, Antarctica, Kiruna, Sweden and Sanriku, Japan using balloon-borne cryogenic air samplers were analyzed for δ^N of Nv and δ^O of O_2. Strength of the gravitational separation was a function of latitude, showing the largest separation inside the polar vortex over Kiruna. It is suggested that information on increase of gravitational separation with height is useful in understanding the vertical transport of air masses in the stratosphere. By comparing the gravitational separations, mean age of air and N_2O concentration at two height intervals with N_2O concentrations > 125 ppb and < 45 ppb, the effect of descending air was found to be more significant over Kiruna than over Syowa Station and Sanriku. The variation in the gravitational separation with height is found to be weaker in the region with N_2O concentrations between 45 and 125 ppb than in other regions, which might suggest that vertical mixing of air occurred in this region

Stratopheric greenhouse gas observation using a balloon-borne cryogenic sampler at Syowa Station, Antarctica

Balloon-borne cryogenic samplers were launched from Japanese Antarctic Station, Syowa, on December 26, 2003 and January 5, 2004. Stratospheric air samples were successfully collected at 11 different altitudes from 10 to 30 km. After air samples were transported to Japan, they were analyzed for various greenhouse gases and their isotopes. The CO_2 concentration, thus obtained, shows no significant vertical gradient above 20 km. Secular increase of CO_2 concentration was clearly observable in the mid-stratosphere over Syowa station. From the average CO_2 concentrations in 1998 and 2004, the concentration difference was calculated to be 9.7 ppm, which is almost same the tropospheric trend. The average mean age was estimated to be 5.0±0.2 years above 20 km. This value was almost the same as that estimated from the CO_2 concentration data in 1998, 4.9±0.2 years. This result implies that there is no secular change of the mean age in the Antarctic stratosphere during this period. Vertical distributions of N_2O isotopomer ratios showed different characteristics among December, January, and previous observations in January 1998, showing that the short-term and long-term effects of transport processes