Flask Air Samples Research Articles

Observed APO Seasonal Cycle in the Pacific: Estimation of Autumn O2 Oceanic Emissions

AbstractIn this work, we investigated the seasonal cycle of atmospheric potential oxygen (APO), a unique tracer of air‐sea gas exchanges of molecular oxygen (O2) and carbon dioxide (CO2), expressed as APO = O2 + 1.1 × CO2. APO data were obtained from flask air samples collected since the late 1990s at three Japanese ground stations and on commercial cargo ships sailing between Japan and Australia/New Zealand, North America, and Southeast Asia. We also analyzed the APO spatial distribution and seasonal cycles with simulations from an atmospheric transport model using climatological oceanic O2 fluxes from an empirical product that relate O2 flux to ocean heat as input. Model simulations reproduced the observed APO seasonal cycles generally well, but with larger amplitudes and earlier occurrence of seasonal minima and maxima than in the observations. Moreover, the observed seasonal cycles exhibited larger APO enhancements than the simulations in autumn and early winter, especially in the North Pacific at 20°N–60°N. These enhancements remained when refining the comparison by adjusting the simulated APO peak‐to‐peak amplitudes and seasonal phases to the observations. This suggests additional O2 emissions in the North Pacific, not well expressed in the air‐sea O2 fluxes used as input for our model simulations. The average autumn enhancement at 40°N–60°N was approximately twice that measured at 20°N–40°N. Confirming previous studies, our results indicate two distinct mechanisms possibly contributing to the additional oceanic O2 emissions: outgassing from a subsurface shallow oxygen maximum at 20°N–40°N and autumn phytoplankton bloom at 40°N–60°N.

Quantification of fossil fuel CO2 from combined CO, δ13CO2 and Δ14CO2 observations

Abstract. We present a new method for partitioning observed CO2 enhancements (CO2xs) into fossil and biospheric fractions (Cff and Cbio) based on measurements of CO and δ13CO2, complemented by flask-based Δ14CO2 measurements. This method additionally partitions the fossil fraction into natural gas and petroleum fractions (when coal combustion is insignificant). Although here we apply the method only to discrete flask air measurements, the advantage of this method (CO- and δ13CO2-based method) is that CO2xs partitioning can be applied at high frequency when continuous measurements of CO and δ13CO2 are available. High-frequency partitioning of CO2xs into Cff and Cbio has already been demonstrated using continuous measurements of CO (CO-based method) and Δ14CO2 measurements from flask air samples. We find that the uncertainty in Cff estimated from the CO- and δ13CO2-based method averages 3.2 ppm (23 % of the mean Cff of 14.2 ppm estimated directly from Δ14CO2), which is significantly less than the CO-based method which has an average uncertainty of 4.8 ppm (34 % of the mean Cff). Using measurements of CO, δ13CO2 and Δ14CO2 from flask air samples at three sites in the greater Los Angeles (LA) region, we find large contributions of biogenic sources that vary by season. On a monthly average, the biogenic signal accounts for −14 to +25 % of CO2xs with larger and positive contributions in winter and smaller and negative contributions in summer due to net respiration and net photosynthesis, respectively. Partitioning Cff into petroleum and natural gas combustion fractions reveals that the largest contribution of natural gas combustion generally occurs in summer, which is likely related to increased electricity generation in LA power plants for air-conditioning.

Background characteristics and influence analysis of greenhouse gases at Akedala regional background station in Northern Xinjiang

Based on the weekly collected flask air samples at Akedala (AKD) Station in northern Xinjiang during 2009–2020, we measured the concentrations of CO2, CH4 and CO and analyzed their long-term variation trend, seasonal characteristics and the influence mechanism of anthropogenic and long-range transport of greenhouse gases at the background station. The results revealed that the background concentrations of CO2 and CH4 at the station experienced an upward trend, while that of CO gradually declined. The CO2 and CH4 background concentrations were 415.69 ± 6.14 ppm and 1976.88 ± 22.26 ppb, respectively, in 2020. The growth rates were 2.41 ppm y−1 and 8.40 ppb y−1 for CO2 and CH4, respectively, during 2009–2020. The background concentration of CO was 128.35 ± 14.83 ppb in 2019 and experienced a downward trend at an average rate of −0.13 ppb y−1 during 2009–2019. The concentrations of CO2, CH4 and CO were all highest in winter. The analysis of the backward trajectory and potential source contribution function revealed the natural and anthropogenic emissions from eastern Kazakhstan, southern Russia, and northern Xinjiang were the main contributors to greenhouse gases concentrations at AKD stations. Moreover, local sources influencing AKD Station were found to be mainly in the southwest direction in winter, reflecting the large anthropogenic emissions in these directions. The results presented here can support a better understanding of the regional/local characteristics of greenhouse gases in the atmosphere of northern Xinjiang against the influence of regional transport, as well as background observations of greenhouse gases in northwestern China and Central Asia.

Analysis of atmospheric greenhouse gases in north Xinjiang

Flask air samples were collected weekly at the Akedala (AKD) regional atmosphere station in north Xinjiang, China, and atmospheric carbon dioxide (CO2) and methane (CH4) mole fractions were measured using cavity-ring down spectroscopy. AKD station is under a typical temperate continental semiarid and arid monsoon climate with westerly air flow. This paper presents the long-term trends and seasonal variations in atmospheric CO2 and CH4 concentrations for the first time and discusses the possible influencing mechanisms. The CO2 and CH4 background mixing ratios were 412.1 ± 0.36 ppm and 1968.9 ± 0.95 ppb, respectively, in 2018. The growth rates were 2.62 ppm y−1 and 9.67 ppb y−1 for CO2 and CH4, respectively, during 2010–2018, which were higher than the surface measurements at Waliguan Baseline Observatory at similar latitudes. The averaged CO2 seasonal cycle showed a minimum in summer and a maximum in winter, and the annual amplitude was high at 18.7 ppm. The CH4 seasonal cycle showed a rapid recovery in summer during July and August. Back-trajectory analysis showed that the atmospheric information at AKD station can provide some implications for uptake from Kazakhstan and Russia, as well as information about natural and anthropogenic emissions in northern Xinjiang. This study revealed that the long-term upward trend of the CO2 concentration in AKD might be attributed to emissions from energy consumption of heavy industry. The comprehensive effects of livestock, geological micro seepage and oil and gas production, and vertical transport also enhanced the atmospheric CH4 concentrations. The results of this study may improve our basic understanding of observed atmospheric CO2 and CH4 in China and Central Asia and the underlying fluxes to be used in atmospheric inversion models.

An indirect-calibration method for non-target quantification of trace gases applied to a time series of fourth-generation synthetic halocarbons at the Taunus Observatory (Germany)

Abstract. Production and use of many synthetic halogenated trace gases are regulated internationally due to their contribution to stratospheric ozone depletion or climate change. In many applications they have been replaced by shorter-lived compounds, which have become measurable in the atmosphere as emissions increased. Non-target monitoring of trace gases rather than targeted measurements of well-known substances is needed to keep up with such changes in the atmospheric composition. We regularly deploy gas chromatography (GC) coupled to time-of-flight mass spectrometry (TOF-MS) for analysis of flask air samples and in situ measurements at the Taunus Observatory, a site in central Germany. TOF-MS acquires data over a continuous mass range that enables a retrospective analysis of the dataset, which can be considered a type of digital air archive. This archive can be used if new substances come into use and their mass spectrometric fingerprint is identified. However, quantifying new replacement halocarbons can be challenging, as mole fractions are generally low, requiring high measurement precision and low detection limits. In addition, calibration can be demanding, as calibration gases may not contain sufficiently high amounts of newly measured substances or the amounts in the calibration gas may have not been quantified. This paper presents an indirect data evaluation approach for TOF-MS data, where the calibration is linked to another compound which could be quantified in the calibration gas. We also present an approach to evaluate the quality of the indirect calibration method, select periods of stable instrument performance and determine well suited reference compounds. The method is applied to three short-lived synthetic halocarbons: HFO-1234yf, HFO-1234ze(E), and HCFO-1233zd(E). They represent replacements for longer-lived hydrofluorocarbons (HFCs) and exhibit increasing mole fractions in the atmosphere. The indirectly calibrated results are compared to directly calibrated measurements using data from TOF-MS canister sample analysis and TOF-MS in situ measurements, which are available for some periods of our dataset. The application of the indirect calibration method on several test cases can result in uncertainties of around 6 % to 11 %. For hydro(chloro-)fluoroolefines (denoted H(C)FOs), uncertainties up to 23 % are achieved. The indirectly calculated mole fractions of the investigated H(C)FOs at Taunus Observatory range between measured mole fractions at urban Dübendorf and Jungfraujoch stations in Switzerland.

Interannual Variability of Atmospheric CH4 and Its Driver Over South Korea Captured by Integrated Data in 2019

Understanding the temporal variability of atmospheric methane (CH4) and its potential drivers can advance the progress toward mitigating changes to the climate. To comprehend interannual variability and spatial characteristics of anomalous CH4 mole fractions and its drivers, we used integrated data from different platforms such as in situ measurements and satellites (TROPOspheric Monitoring Instrument (TROPOMI) and Greenhouse Gases Observing SATellite (GOSAT)) retrievals. A pronounced change of annual growth rate was detected at Anmyeondo (AMY), Republic of Korea, ranging from −16.8 to 31.3 ppb yr−1 as captured in situ through 2015–2020 and 3.9 to 16.4 ppb yr−1 detected by GOSAT through 2014–2019, respectively. High growth rates were discerned in 2016 (31.3 ppb yr−1 and 13.4 ppb yr−1 from in situ and GOSAT, respectively) and 2019 (27.4 ppb yr−1 and 16.4 ppb yr−1 from in situ and GOSAT, respectively). The high growth in 2016 was essentially explained by the strong El Niño event in 2015–2016, whereas the large growth rate in 2019 was not related to ENSO. We suggest that the growth rate that appeared in 2019 was related to soil temperature according to the Noah Land Surface Model. The stable isotopic composition of 13C/12C in CH4 (δ13-CH4) collected by flask-air sampling at AMY during 2014–2019 supported the soil methane hypothesis. The intercept of the Keeling plot for summer and autumn were found to be −53.3‰ and −52.9‰, respectively, which suggested isotopic signature of biogenic emissions. The isotopic values in 2019 exhibited the strongest depletion compared to other periods, which suggests even a stronger biogenic signal. Such changes in the biogenic signal were affected by the variations of soil temperature and soil moisture. We looked more closely at the variability of XCH4 and the relationship with soil properties. The result indicated a spatial distribution of interannual variability, as well as the captured elevated anomaly over the southwest of the domain in autumn 2019, up to 70 ppb, which was largely explained by the combined effect of soil temperature and soil moisture changes, indicating a pixel-wise correlation of XCH4 anomaly with those parameters in the range of 0.5–0.8 with a statistical significance (p < 0.05). This implies that the soil-associated drivers are able to exert a large-scale influence on the regional distribution of CH4 in Korea.

Observations of atmospheric 14CO2 at Anmyeondo GAW station, South Korea: implications for fossil fuel CO2 and emission ratios

Abstract. To understand the Korean Peninsula's carbon dioxide (CO2) emissions and sinks as well as those of the surrounding region, we used 70 flask-air samples collected during May 2014 to August 2016 at Anmyeondo (AMY; 36.53∘ N, 126.32∘ E; 46 m a.s.l.) World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) station, located on the west coast of South Korea, for analysis of observed 14C in atmospheric CO2 as a tracer of fossil fuel CO2 contribution (Cff). Observed 14C ∕ C ratios in CO2 (reported as Δ values) at AMY varied from −59.5 ‰ to 23.1 ‰, with a measurement uncertainty of ±1.8 ‰. The derived mean value Cff of (9.7±7.8) µmol mol−1 (1σ) is greater than that found in earlier observations from Tae-Ahn Peninsula (TAP; 36.73∘ N, 126.13∘ E; 20 m a.s.l., 28 km away from AMY) of (4.4±5.7) µmol mol−1 from 2004 to 2010. The enhancement above background mole fractions of sulfur hexafluoride (Δx(SF6)) and carbon monoxide (Δx(CO)) correlate strongly with Cff (r>0.7) and appear to be good proxies for fossil fuel CO2 at regional and continental scales. Samples originating from the Asian continent had greater Δx(CO) : Cff(RCO) values, (29±8) to (36±2) nmol µmol−1, than in Korean Peninsula local air ((8±2) nmol µmol−1). Air masses originating in China showed (1.6±0.4) to (2.0±0.1) times greater RCO than a bottom-up inventory, suggesting that China's CO emissions are underestimated in the inventory, while observed RSF6 values are 2–3 times greater than inventories for both China and South Korea. However, RCO values derived from both inventories and observations have decreased relative to previous studies, indicating that combustion efficiency is increasing in both China and South Korea.

A Cryogen-Free Automated Measurement System of Stable Carbon Isotope Ratio of Atmospheric Methane

Although methane plays an important role in climate change and atmospheric chemistry, its global budget remains quantitatively uncertain mainly because of a wide variety of source types. The stable carbon isotope ratio of atmospheric methane (δ13C-CH4) is useful for separating contributions of different source categories, but owing to the complex and laborious analysis, limited measurement data exist. We present a new system for δ13C-CH4 measurement, optimized for the automated analysis of air samples. Although the system is designed, in principle, similarly to those in previous studies, we successfully set up the system with no use of cryogens (e.g., liquid nitrogen) and attained reproducibility sufficient to analyze atmospheric variations (∼0.1 ‰). We performed automated continuous measurements of ambient air outside our laboratory at about hourly intervals for 2 months, which characterized imprint of local methane sources well. Future measurement operation for flask air samples from existing atmospheric monitoring programs will provide a large number of atmospheric δ13C-CH4 data.

Automated simultaneous measurement of the δ(13) C and δ(2) H values of methane and the δ(13) C and δ(18) O values of carbon dioxide in flask air samples using a new multi cryo-trap/gas chromatography/isotope ratio mass spectrometry system.

The isotopic composition of greenhouse gases helps to constrain global budgets and to study sink and source processes. We present a new system for high-precision stable isotope measurements of carbon, hydrogen and oxygen in atmospheric methane and carbon dioxide. The design is intended for analyzing flask air samples from existing sampling programs without the need for extra sample air for methane analysis. CO2 and CH4 isotopes are measured simultaneously using two isotope ratio mass spectrometers, one for the analysis of δ(13) C and δ(18) O values and the second one for δ(2) H values. The inlet carousel delivers air from 16 sample positions (glass flasks 1-5 L and high-pressure cylinders). Three 10-port valves take aliquots from the sample stream. CH4 from 100-mL air aliquots is preconcentrated in 0.8-mL sample loops using a new cryo-trap system. A precisely calibrated working reference air is used in parallel with the sample according to the Principle of Identical Treatment. It takes about 36 hours for a fully calibrated analysis of a complete carousel including extractions of four working reference and one quality control reference air. Long-term precision values, as obtained from the quality control reference gas since 2012, account for 0.04 ‰ (δ(13) C values of CO2 ), 0.07 ‰ (δ(18) O values of CO2 ), 0.11 ‰ (δ(13) C values of CH4 ) and 1.0 ‰ (δ(2) H values of CH4 ). Within a single day, the system exhibits a typical methane δ(13) C standard deviation (1σ) of 0.06 ‰ for 10 repeated measurements. The system has been in routine operation at the MPI-BGC since 2012. Consistency of the data and compatibility with results from other laboratories at a high precision level are of utmost importance. A high sample throughput and reliability of operation are important achievements of the presented system to cope with the large number of air samples to be analyzed. Copyright © 2016 John Wiley & Sons, Ltd.

한반도 지역에서의 이산화탄소 변화 경향과 AIRS, GOSAT 위성 자료의 정확도 비교

지구 온난화와 기후 시스템에 가장 강력한 영향을 미치는 인자 중 하나인 대기 중 이산화탄소 농도 변화를 지속적으로 모니터링하는 것은 중요하며, 현재 지상 관측과 더불어 위성을 통한 모니터링이 이루어지고 있다. 본 연구에서는 동북아시아 지역 중에서도 1999년부터 주요 대기질 관측소로 운영되어 온 안면도와 고산에서의 대기 중 이산화탄소 농도 변화에 대한 경향성을 전구 월별 평균 값과 비교해 보았으며, 이를 대표적인 온실 기체 관측 위성인 Greenhouse Gases Observing Satellite (GOSAT)과 Atmospheric Infrared Sounder (AIRS)에서 산출되는 값을 안면도와 고산 관측소의 농도 값과 비교하였다. 1999년 1월 대기 중 평균 농도가 371.87 ppm이었던 안면도에서의 이산화탄소 농도는 2013년 12월 405.50 ppm으로 지난 15년간 지속적으로 증가하였다(KMA, 2013). 플라스크 공기 샘플링 방법에 의해 관측된 안면도의 이산화탄소 농도는 같은 기간 전구의 계절 변동성 및 증가 추이가 동일했으나, 동북아시아에서의 이산화탄소 농도의 증가폭이 전구보다 평균 4 ppm 더 높게 나타났다. GOSAT과 AIRS에서 산출된 이산화탄소는 안면도 관측소의 지상 농도와 비교되었으며, 이를 통해 두 위성 자료들의 정확도가 비교하고자 하였다. GOSAT과 AIRS 모두 월별 이산화탄소 농도는 지상 관측소인 안면도의 관측 값보다는 낮은 분포 경향을 보였으나, 계절 변동성과 증가 추이는 동일하게 나타났다. GOSAT과 AIRS에서 산출되는 이산화탄소 농도는 위성별 정확도 분석을 위해 두 위성의 관측 기간 중 동일 관측이 수행된 2011년 1월부터 2012년 12월까지의 자료를 비교하였다. GOSAT은 r이 0.947, RMSD가 5.610, bias가 -5.280으로 r이 0.737, RMSD가 8.574, bias가 -7.316으로 나타난 AIRS보다 동북아시아를 대표하는 안면도 관측소에서의 정확도가 더 높게 나타났다. With the global scale impact of atmospheric <TEX>$CO_2$</TEX> in global warming and climate system, it is necessary to monitor the <TEX>$CO_2$</TEX> concentration continuously on a global scale, where satellite remote sensing has played a significant role recently. In this study, global monthly <TEX>$CO_2$</TEX> concentrations obtained by satellite remote sensing were compared with ground-based measurements at Anmyeon-do and Gosan Korean Global Atmosphere Watch Center. Atmospheric <TEX>$CO_2$</TEX> concentration has increased from 371.87 ppm in January 1999 to 405.50 ppm in December 2013 at Anmyeon-do station (KMA, 2013). Comparison of the continuous measurements by flask air sampling at Anmyeon-do shows the same trend and seasonal variations with those of global monthly mean dataset. Nevertheless, the trends of <TEX>$CO_2$</TEX> over Northeast Asia showed the higher than those of global and the trends also changes with different slope. <TEX>$CO_2$</TEX> products derived from Greenhouse Gases Observing Satellite (GOSAT) and Atmospheric Infrared Sounder (AIRS) were compared with ground-based measurement at Anmyeon-do. The monthly mean values of GOSAT and AIRS data are systemically lower than those obtained at Anmyeon-do, however, the seasonal cycle of satellite products present the similar trend with values of global and Anmyeon-do. The accuracy of <TEX>$CO_2$</TEX> products from GOSAT and AIRS were evaluated statistically for two years from January 2011 to December 2012. GOSAT showed good correlation with the correlation coefficient, RMSD and bias of 0.947, 5.610 and -5.280 to ground-based measurements respectively, while AIRS showed reasonable comparison with 0.737, 8.574 and -7.316 at Anmyeon-do station, respectively.

High-precision quasi-continuous atmospheric greenhouse gas measurements at Trainou tower (Orléans forest, France)

Abstract. Results from the Trainou tall tower measurement station installed in 2006 are presented for atmospheric measurements of CO2, CH4, N2O, SF6, CO, H2 mole fractions and radon-222 activity. Air is sampled from four sampling heights (180, 100, 50 and 5 m) of the Trainou 200 m television tower in the Orléans forest in France (47°57'53" N, 2°06'45" E, 131 m a.s.l.). The station is equipped with a custom-built CO2 analyser (CARIBOU), which is based on a commercial non-dispersive, infrared (NDIR) analyser (Licor 6252), and a coupled gas chromatography (GC) system equipped with an electron capture detector (ECD) and a flame ionization detector (FID) (HP6890N, Agilent) and a reduction gas detector (PP1, Peak Performer). Air intakes, pumping and air drying system are shared between the CARIBOU and the GC systems. The ultimately achieved short-term repeatability (1 sigma, over several days) for the GC system is 0.05 ppm for CO2, 1.4 ppb for CH4, 0.25 ppb for N2O, 0.08 ppb for SF6, 0.88 ppb for CO and 3.8 for H2. The repeatability of the CARIBOU CO2 analyser is 0.06 ppm. In addition to the in situ measurements, weekly flask sampling is performed, and flask air samples are analysed at the Laboratoire des Sciences du Climat et de l'Environnement (LSCE) central laboratory for the same species as well for stable isotopes of CO2. The comparison between in situ measurements and the flask sampling showed averaged differences of 0.08 ± 1.40 ppm for CO2, 0.7 ± 7.3 ppb for CH4, 0.6 ± 0.6 ppb for N2O, 0.01 ± 0.10 ppt for SF6, 1.5± 5.3 ppb for CO and 4.8± 6.9 ppb for H2 for the years 2008–2012. At Trainou station, the mean annual increase rates from 2007 to 2011 at the 180 m sampling height were 2.2 ppm yr−1 for CO2, 4 ppb yr−1 for CH4, 0.78 ppb yr−1 for N2O and 0.29 ppt yr−1 for SF6. For all species, the 180 m sampling level showed the smallest diurnal variation. Mean diurnal gradients between the 50 m and the 180 m sampling level reached up to 30 ppm CO2, 15 ppm CH4 or 0.5 ppb N2O during nighttime whereas the mean gradients are smaller than 0.5 ppm for CO2 and 1.5 ppb for CH4 during afternoon.

HFC-43-10mee atmospheric abundances and global emission estimates

We report in situ atmospheric measurements of hydrofluorocarbon HFC-43-10mee (C5H2F10; 1,1,1,2,2,3,4,5,5,5-decafluoropentane) from seven observatories at various latitudes, together with measurements of archived air samples and recent Antarctic flask air samples. The global mean tropospheric abundance was 0.21 ± 0.05 ppt (parts per trillion, dry air mole fraction) in 2012, rising from 0.04 ± 0.03 ppt in 2000. We combine the measurements with a model and an inverse method to estimate rising global emissions—from 0.43 ± 0.34 Gg yr−1 in 2000 to 1.13 ± 0.31 Gg yr−1 in 2012 (~1.9 Tg CO2-eq yr−1 based on a 100 year global warming potential of 1660). HFC-43-10mee—a cleaning solvent used in the electronics industry—is currently a minor contributor to global radiative forcing relative to total HFCs; however, our calculated emissions highlight a significant difference from the available reported figures and projected estimates.

Evaluation of a new JMA aircraft flask sampling system and laboratory trace gas analysis system

Abstract. We established and evaluated a flask air sampling system on a cargo C-130H aircraft, as well as a trace gas measurement system for the flask samples, as part of a new operational monitoring program of the Japan Meteorological Agency (JMA). Air samples were collected during each flight, between Kanagawa Prefecture (near Tokyo) and Minamitorishima (an island located nearly 2000 km southeast of Tokyo), from the air-conditioning system on the aircraft. Prior to the operational employment of the sampling system, a quality assurance test of the sampled air was made by specially coordinated flights at a low altitude of 1000 ft over Minamitorishima and comparing the flask values with those obtained at the surface. Based on our storage tests, the flask samples remained nearly stable until analyses. The trace gas measurement system has, in addition to the nondispersive infrared (NDIR) and vacuum ultraviolet resonance fluorescence (VURF) analyzers, two laser-based analyzers using wavelength-scanned cavity ring-down spectroscopy (WS-CRDS) and off-axis integrated cavity output spectroscopy (ICOS). Laboratory tests of the laser-based analyzers for measuring flask samples indicated relatively high reproducibility with overall precisions of less than ±0.06 ppm for CO2, ±0.68 ppb for CH4, ±0.36 ppb for CO, and ±0.03 ppb for N2O. Flask air sample measurements, conducted concurrently on different analyzers were compared. These comparisons showed a negligible bias in the averaged measurements between the laser-based measurement techniques and the other methods currently in use. We also estimated that there are no significant isotope effects for CH4, CO and N2O using standard gases with industrial isotopic compositions to calibrate the laser-based analyzers, but CO2 was found to possess isotope effects larger than its analytical precision.

Variation of CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; mole fraction in the lower free troposphere, in the boundary layer and at the surface

Abstract. Eight years of occasional flask air sampling and 3 years of frequent in situ measurements of carbon dioxide (CO2) vertical profiles on board of a small aircraft, over a tall tower greenhouse gases monitoring site in Hungary are used for the analysis of the variations of vertical profile of CO2 mole fraction. Using the airborne vertical profiles and the measurements along the 115 m tall tower it is shown that the measurements at the top of the tower estimate the mean boundary layer CO2 mole fraction during the mid-afternoon fairly well, with an underestimation of 0.27–0.85 μmol mol−1 in summer, and an overestimation of 0.66–1.83 μmol mol−1 in winter. The seasonal cycle of CO2 mole fraction is damped with elevation. While the amplitude of the seasonal cycle is 28.5 μmol mol−1 at 10 m above the ground, it is only 10.7 μmol mol−1 in the layer of 2500–3000 m corresponding to the lower free atmosphere above the well-mixed boundary layer. The maximum mole fraction in the layer of 2500–3000 m can be observed around 25 March on average, two weeks ahead of that of the marine boundary layer reference (GLOBALVIEW). By contrast, close to the ground, the maximum CO2 mole fraction is observed late December, early January. The specific seasonal behavior is attributed to the climatology of vertical mixing of the atmosphere in the Carpathian Basin.

Atmospheric CO2 concentrations and δ13C values between New Zealand and Antarctica, 1998 to 2010: some puzzling results

ABSTRACTFrom 1998 to 2010, during eight cruises of the M/V Italica between New Zealand and Antarctica, sets of flask air samples were collected and atmospheric CO2 concentrations were recorded. The δ13C of CO2 from the 1998 to 2003 air samples have already been published and show large interannual variability and an increasing frequency of 13C-depleted samples. These results were related to a mosaic of areas with positive air–sea fluxes. We report here δ13C results from air samples collected from four further cruises. δ13C values obtained during the 2004/2005 cruise show an inexplicable saw-toothed distribution. Air samples from the 2005/2006 cruise have δ13C values which match previous sets of samples (1998 to 2004) and show more frequent and more negative isotopic events. From 2006 until 2009, further samples could not be collected. However, during December 2009 and January 2010, two more sets of air samples were collected, the δ13C values of which greatly differ from previous results, being absolutely homogeneous and paralleled by flat CO2 concentrations. The results of these last two sets of air samples may be due either to fortuitous environmental conditions or to an improbable and substantial change in oceanic and atmospheric conditions in this section of the circumpolar area.

Atmospheric CO2 concentrations and δ13C over western and eastern Mediterranean basins during summer 2007

Abstract During summer 2007, two survey cruises covered large sections of both western and eastern Mediterranean basins. Atmospheric CO2 concentrations were measured with a Siemens Ultramat 5E analyser on both outward and return voyages, and 48 discrete air samples were collected with evacuated Pyrex flasks. The δ13C values of the CO2 from the flask air samples were measured in the laboratory following well-established procedures. CO2 concentrations in the western basin were characterised by marked variations, ranging from about 381 to about 394 ppmv. Peaks of up to 398 and 415 ppmv were occasionally recorded, in particular close to the Strait of Gibraltar. The δ13C values were very homogeneous, with a mean value of −9.70 ± 0.22‰, in contrast with the large δ13C fluctuations expected in this basin. The eastern basin, on average, showed far lower CO2 concentrations than those recorded in the western one. The overall range was between about 375 and 398 ppmv, but most values fell between 375 and 388 ppmv. The δ13C values of the discrete air samples were also very homogeneous, with a mean value of −9.37 ± 0.16‰, less negative than that of the western basin. The CO2 concentrations were slightly lower than those measured in December 2007 in the eastern Mediterranean in contrast with the hypothesis of heavy summer pollution in the Mediterranean basins. No quantitative relationship was found between CO2 concentrations and δ13C values. This discrepancy may be the effect of the large biospheric sink of CO2 on land and of the plant isotopic discrimination against 13C.

Decadal changes in atmospheric CO 2 concentration and δ 13C over two seas and two oceans: Italy to New Zealand

Continuous measurements of the CO 2 concentration were repeatedly carried out from 1996 to 2007 between Italy and New Zealand by means of a Siemens Ultramat 5E analyzer assembled for shipboard use. Along the ship routes discrete air samples were collected from 1998 to 2005 using four-litre Pyrex flasks. The δ 13C of the CO 2 from the flask air samples was measured according to well-established techniques. The decadal changes of these two variables can now be evaluated from these results. Large variations of the CO 2 concentration were normally recorded in the Mediterranean and the Red Sea. Completely different trends of the CO 2 concentration were observed in the Red Sea (30° N to about 13° N) between 2007 (a marked southward decrease) and 2005 and 2003 when a marked southward increase is apparent, at least between 23° and 13° N. A further difference among different expeditions is related to the decrease or increase of the CO 2 concentration in the Gulf of Aden. The backward trajectories of the air masses help to explain, at least partially, these differences. In the Indian Ocean and Southern Ocean a decrease of a few ppmv of the CO 2 concentration takes place from Cape Guardafui (Northern Somaliland) to southern New Zealand, particularly during 2005 and 2007. The yearly rate of increase of the CO 2 concentration between 1996 and 2007 for the Indian Ocean is of about 1.9 ppmv yr −1, in excellent agreement with the NOAA/CMDL measurements carried out during the same period at Mahé Isld. (Indian Ocean) and Cape Grim (Tasmania). The δ 13C results obtained from the CO 2 of flask samples collected in the Mediterranean show the effect of anthropogenic emissions, though this is considerably smaller than expected. This inconsistency may be related to the large terrestrial biospheric sink of CO 2 in the Northern Hemisphere. The results obtained from the Red Sea are quite variable through time and space, particularly in its southern section; their interpretation is not easy. The Indian Ocean and the Southern Ocean show rather homogeneous δ 13C results even though a variable carbon isotope shift can be calculated from period/cruise to period/cruise. In the case of the Indian Ocean the mean δ 13C value from the flask air samples collected in 2005 is −8.29‰ and the calculated rate of the carbon isotope shift between 1998 and 2005 is −0.034‰ yr −1, considerably larger than that calculated at the closest NOAA station (Mahé Isld.) of −0.026‰ yr −1. This discrepancy may be, at least partially, caused by the small number of measurements carried out at sea. However, the atmosphere over the Indian Ocean is less affected by anthropogenic emissions than in other areas.

Temporal and spatial variations of the atmospheric CO2 concentration in China

In order to understand the variations of atmospheric greenhouse gases over the Chinese mainland, an air sampling network was established in March 2003 that included one GAW global station, three GAW regional stations and three cooperative stations. Flask air samples were taken every week at the stations for 3 years. The secular increase and the seasonal variation in the CO2 concentration are clearly observable at all the stations, reflecting global as well as the regional terrestrial biospheric and human activities, as well as the local meteorological conditions. The average CO2 concentration depends on the station, with the lowest value observed at Mt. Waliguan and relatively high values observed at Fukang and Lin‐an stations, located in the westernmost and eastern parts of China, respectively. The observed CO2 concentration variations are also discussed within the context of forward transport model simulations using CO2 fluxes derived by time‐dependent inversion.

Evaluation of atmospheric CO2 measurements from new flask air sampling of JAL airliner observations

2005年12月以降、新しい空気採取装置（ASE）を利用して、オーストラリアと日本を結ぶJALの旅客機によって西部太平洋上の高度約10kmにおける大気中二酸化炭素(CO2)の測定結果を収集した。ASEで観測されたCO2は、同じフライトで観測した二酸化炭素連続測定装置（CME）の結果と非常に良く一致していた。また、ASEのデータは高時間分解能を持つCMEのデータに比べて観測密度が粗いが、両データとも、北緯30度から南緯30度までを5度間隔で分割した緯度帯平均のCO2濃度は、近い値を示した。JAL旅客機による新旧観測において一貫したデータセットを作成するために、気象研究所と国立環境研究所で使用しているCO2標準ガスのスケールを比較した。新観測で得られたCO2のデータには明瞭な季節変化と増加傾向が見られ、それらは、過去12年間の旧観測で得られたCO2変動の気候値の外挿から再現された変動とほぼ一致していた。特に、新観測において、長期的トレンドを除去した季節変動の緯度帯変化は、旧観測の気候値から得られるものと極めて良く類似していた。これらの結果から、JAL旅客機による新旧の観測データが一貫した連続性を保っていることが示された。

Regional CO2fluxes inferred from mixing ratio measurements: estimates from flask air samples in central Kansas, USA

Regional CO₂fluxes inferred from mixing ratio measurements: estimates from flask air samples in central Kansas, USA