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An in situ measurement system was developed for continuous observations of the mole fractions of atmospheric oxygen (defined as δ(O2/N2)) and carbon dioxide (CO2) and the continuous observation was conducted onboard the research vessel SHIRASE 5003 during its voyage between Australia and Syowa Station, Antarctica, in 2017–2018. The CO2 variation was low with respect to that of δ(O2/N2) in the Southern Ocean, suggesting that the land biospheric and fossil-fuel derived CO2 and O2 emissions negligibly influenced the observations. Therefore, the observed significant variations in the atmospheric O2/N2 can be attributed to the atmosphere-ocean gas exchange. During the southbound voyage in December 2017, we observed large spatial variations in δ(O2/N2) due to marine biological production on the western side of the cruise track. Oceanic O2 fluxes based on a simple model and atmospheric δ(O2/N2) variability were consistent with past oceanic observations. No clear longitudinal gradient in δ(O2/N2) was observed at latitudes toward south of 60° S in December 2017 and February–March 2018. However, local δ(O2/N2) maxima were observed in regions with active marine biological production in December 2017. These observations indicate that local O2 fluxes can also modify the spatial distribution of atmospheric δ(O2/N2) in the Southern Ocean.

Systematic observations of CO2 mole fraction, the isotopic ratio δ13C of CO2 and oxygen to nitrogen ratio (δ(O2/N2)) in the atmosphere have been carried out at Ny-Alesund, Svalbard since 1991, 1996 and 2001, respectively. The CO2 mole fraction shows a clear seasonal cycle superimposed on a secular increase with an average rate of 2.0 ppm yr−1 for the period 1996–2013. On the other hand, δ13C and δ(O2/N2) decrease secularly at an average rate of −0.020 ‰ yr−1 for 1996–2013, and −19.9 per meg yr−1 for 2001–2013, respectively. Based on the observed secular trends of the CO2 mole fraction and δ(O2/N2), the average CO2 uptake during 2001–2013 was estimated to be 1.6 ± 0.8 and 2.3 ± 0.5 GtC yr−1 for the terrestrial biosphere and the ocean, respectively. By using the observed CO2 and δ13C, the corresponding CO2 uptake of 1.3 ± 0.6 and 2.6 ± 0.5 GtC yr−1 were obtained for the same period. The estimates from the two methods are in good agreement with each other. The terrestrial biospheric CO2 uptake derived by the latter method showed large inter-annual variability in association with El Nino events. On the other hand, the oceanic uptake increased secularly with less inter-annual variability during 1996–2013.

Atmospheric methane (CH4) increased from ~900 ppb (parts per billion, or nanomoles per mole of dry air) in 1900 to ~1800 ppb in 2010 at a rate unprecedented in any observational records. However, the contributions of the various methane sources and sinks to the CH4 increase are poorly understood. Here we use initial emissions from bottom-up inventories for anthropogenic sources, emissions from wetlands and rice paddies simulated by a~terrestrial biogeochemical model, and an atmospheric general circulation model (AGCM)-based chemistry-transport model (i.e. ACTM) to simulate atmospheric CH4 concentrations for 1910–2010. The ACTM simulations are compared with the CH4 concentration records reconstructed from Antarctic and Arctic ice cores and firn air samples, and from direct measurements since the 1980s at multiple sites around the globe. The differences between ACTM simulations and observed CH4 concentrations are minimized to optimize the global total emissions using a mass balance calculation. During 1910–2010, the global total CH4 emission doubled from ~290 to ~580 Tg yr−1. Compared to optimized emission, the bottom-up emission data set underestimates the rate of change of global total CH4 emissions by ~30% during the high growth period of 1940–1990, while it overestimates by ~380% during the low growth period of 1990–2010. Further, using the CH4 stable carbon isotopic data (δ13C), we attribute the emission increase during 1940–1990 primarily to enhancement of biomass burning. The total lifetime of CH4 shortened from 9.4 yr during 1910–1919 to 9 yr during 2000–2009 by the combined effect of the increasing abundance of atomic chlorine radicals (Cl) and increases in average air temperature. We show that changes of CH4 loss rate due to increased tropospheric air temperature and CH4 loss due to Cl in the stratosphere are important sources of uncertainty to more accurately estimate the global CH4 budget from δ13C observations.

We present a comprehensive estimate of nitrous oxide (N2O) emissions using observations and models from 1995 to 2008. High-frequency records of tropospheric N2O are available from measurements at Cape Grim, Tasmania; Cape Matatula, American Samoa; Ragged Point, Barbados; Mace Head, Ireland; and at Trinidad Head, California using the Advanced Global Atmospheric Gases Experiment (AGAGE) instrumentation and calibrations. The Global Monitoring Division of the National Oceanic and Atmospheric Administration/Earth System Research Laboratory (NOAA/ESRL) has also collected discrete air samples in flasks and in situ measurements from remote sites across the globe and analyzed them for a suite of species including N2O. In addition to these major networks, we include in situ and aircraft measurements from the National Institute of Environmental Studies (NIES) and flask measurements from the Tohoku University and Commonwealth Scientific and Industrial Research Organization (CSIRO) networks. All measurements show increasing atmospheric mole fractions of N2O, with a varying growth rate of 0.1–0.7% per year, resulting in a 7.4% increase in the background atmospheric mole fraction between 1979 and 2011. Using existing emission inventories as well as bottom-up process modeling results, we first create globally gridded a priori N2O emissions over the 37 years since 1975. We then use the three-dimensional chemical transport model, Model for Ozone and Related Chemical Tracers version 4 (MOZART v4), and a Bayesian inverse method to estimate global as well as regional annual emissions for five source sectors from 13 regions in the world. This is the first time that all of these measurements from multiple networks have been combined to determine emissions. Our inversion indicates that global and regional N2O emissions have an increasing trend between 1995 and 2008. Despite large uncertainties, a significant increase is seen from the Asian agricultural sector in recent years, most likely due to an increase in the use of nitrogenous fertilizers, as has been suggested by previous studies.

Systematic collections of stratospheric air samples have been conducted over Japan since 1985 using a balloon-borne cryogenic sampler. The collection of stratospheric air samples was also carried out twice over Scandinavia and once over Antarctica. Vertical profiles of CO 2 concentration thus obtained over these locations were quite similar to each other; CO 2 concentration decreased with increasing altitude in the lower stratosphere and reached an almost constant value in the mid-stratosphere. δ 13 C of stratospheric CO 2 observed over these locations enriched with increasing altitude. A negative correlation between δ 13 C and CO 2 concentration with Δδ 13 C/ΔCO 2 of −0.02‰ ppmv −1 was found in the lower stratosphere. Although CO 2 concentration was almost constant in the mid-stratosphere, the δ 13 C enrichment was observed in succession. δ 18 O of stratospheric CO 2 also enriched with increasing altitude. The enrichment was significant; δ 18 O was almost 0‰ at the tropopause and reached a maximum value of about 11‰ at a layer with N 2 O concentration of about 10 ppbv. A compact relation between δ 18 O and N 2 O concentration was consistently observed for these locations. Stratosperic CO 2 over Japan showed a secular increase with an average rate of 1.4 ppmv yr −1 for the period 1985–2000. The secular increase was not constant with time, and temporal stagnation of the CO 2 increase was observed in 1997. DOI: 10.1034/j.1600-0889.2003.00059.x

Aircraft measurements of the tropospheric N2O concentration were made over Japan during the period from October 1991 to June 1999. The observed values of the N2O concentration showed clear evidence of the secular increase, with mean rates of 0.50 to 0.64 ppbv/yr for selected height intervals of 0–2, 2–4, 4–6, 6–8 km and 8 km-tropopause. Although the seasonality of the N2O concentration was hardly observable throughout the troposphere, interannual variations with periods of about 2 years were clearly found. The average N2O concentrations over the observation period for the above 5 height intervals were almost identical with each other, showing no appreciable vertical gradient of the concentration. This suggests that N2O emissions from the ground surface around Japan are very weak and the emitted N2O is mixed well in the troposphere.

Net CO 2 fluxes between the atmosphere and the ocean, and between the atmosphere and the terrestrial biosphere, were estimated by constraining a two-dimensional atmospheric transport model with the CO 2 concentration and its δ 13 C data obtained from our shipboard measurements in the western Pacific region during the period April 1984 to December 1991. The results obtained for the non-El Nino and Southern Oscillation (ENSO) years during this time period showed that the ocean acted as a CO 2 sink in middle latitudes of both hemispheres and a CO 2 source around the equator. The results also suggested that during the 1984-1991 period there were biospheric CO 2 sources in southern low and northern middle latitudes, and significant biospheric sinks in northern high latitudes. By comparing the latitudinal distributions of CO 2 source/sink for ENSO years with those for non-ENSO years, it was found that a considerable amount of CO 2 was released from the terrestrial biosphere in low latitudes in association with the 1986-1987 ENSO event. While the oceanic region from the equator to 30°N acted as an excess CO 2 sink of about 1.0 Gt C yr -1 during 1987 and 1988, the oceanic contributions to the CO 2 anomaly in the atmosphere were less pronounced in the northern high latitudes and in the southern hemisphere. Also, compared with the estimated interannual fluctuations in the atmosphere-biosphere CO 2 flux, the net CO 2 flux between the atmosphere and the ocean showed relatively less interannual variability.

The global distribution of atmospheric methyl bromide (CH 3 Br) obtained from extensive new measurements of atmospheric CH 3 Br from latitude 82.5°N to 69.1°S, showed a small decrease from mid- to high-latitudes, a gradient between the northern and southern hemispheres with a ratio of 1.2 to 1.3, and occasional high concentrations in the tropics. The observed data and modeled distributions of industrial CH 3 Br were used to apportion CH 3 Br between natural and industrial components for both hemisphere. We obtained an estimated man-made contribution of 4.3 pptv and 2.3 pptv in the northern and southern hemispheres, respectively and a natural (non-industrial) background concentration in both hemispheres of 6 pptv with a slight increase in the tropics.

Sampling for atmospheric isoprene and some other volatile organic compounds was conducted during two cruises in the austral summer, covering the western Pacific, eastern Indian Ocean, Southeast Asian Sea, and Southern Ocean. High isoprene levels were observed in the marine air masses over the southern Indian Ocean (up to 280 parts per trillion by volume (pptv)) and over the Southern Ocean (up to 60 pptv), as well as high levels of dimethyl sulfide and bromoform, both of which are mainly emitted by marine biota. It is highly probable that the high phytoplankton activity in the Southern Ocean during the austral summer was responsible for the high oceanic isoprene levels. The findings suggest a possible significant influence of oceanic isoprene on marine atmospheric chemistry.

High O3 mixing ratios were observed above 6 km over Syowa Station (SYO), Antarctica in mid-September 1989 when the tropopause was found to be higher than 10 km. From the results of a 3-dimensional trajectory analysis, it is suggested that the observed high O3 was caused by vertical transport of O3 from the lower stratosphere to the upper troposphere. To examine general features of the transport process associated with high O3 mixing ratios observed in the upper troposphere over SYO, the same trajectory analysis was further performed for high O3 observations at 350 hPa over SYO in 1987–1994. The results imply that the transport of stratospheric air descending in the polar region to SYO plays a very important role in the increase of upper tropospheric O3 over SYO, especially in spring and autumn, while the downward transport of stratospheric O3 in the circumpolar region is important in summer.

The dynamics of tropospheric ozone variations in the Arctic (Ny-A lesund, Spitsbergen, 79°N, 12°E) and in Antarctica (Neumayer-Station, 70°S, 8°W) were investigated for the period January 1993 to June 1994. Continuous surface ozone measurements, vertical profiles of tropospheric ozone by ECC-sondes, meteorological parameters, trajectories as well as ice charts were available for analysis. Information about the origins of the advected air masses were derived from 5-days back-trajectory analyses. Seven tropospheric ozone minima were observed at Ny-A lesund in the period from March to June 1994, during which the surface ozone mixing ratios decreased from typical background concentrations around 40 ppbv to values between 1 ppbv and 17 ppbv (1 ppbv O 3 corresponds to one part of O 3 in 10 9 parts of ambient air by volume). Four surface ozone minima were detected in August and September 1993 at Neumayer-Station with absolute ozone mixing ratios between 8 ppbv and 14 ppbv throughout the minima. At both measuring stations, the ozone minima were detected during polar spring. They covered periods between 1 and 4 days (Arctic) and 1 and 2 days (Antarctica), respectively. Furthermore, it was found that in both polar regions, the ozone depletion events were confined to the planetary boundary layer with a capping temperature inversion at the upper limit of the ozone poor air mass. Inside this ozone- poor layer, a stable stratification was obvious. Back-trajectory analyses revealed that the ozone-depleted air masses were transported across the marine, ice-covered regions of the central Arctic and the South Atlantic Ocean. These comparable observations in both polar regions suggest a similar ozone destruction mechanism which is responsible for an efficient ozone decay. Nevertheless, distinct differences could be found regarding the vertical structure of the ozone depleted layers. In the Arctic, the ozone-poor layer developed from the surface up to a temperature inversion, whereas in the Antarctic, elevated ozone-depleted air masses due to the influence of catabatic surface winds, were observed. DOI: 10.1034/j.1600-0889.1998.00003.x

[1] Aircraft measurements of carbon and hydrogen isotopic ratios of atmospheric CH4 (δ13CH4 and δD-CH4), with the respective precisions of 0.08‰ and 2.2‰, as well as CH4 concentration were made at 1 and 2 km altitudes over western Siberia during 2006–2009. δ13CH4 and δD-CH4 were almost always lower at lower altitudes, while the CH4 concentration was higher, implying strong sources on the ground with low isotopic values. δ13CH4 showed a clear seasonal minimum in the late summer, while seasonality of CH4 and δD-CH4 was ambiguous due to the local disturbances. By inspecting the relationships between the CH4 concentration and isotopes, we found that isotopic source signatures in the winter (December–April) are −41.2 ± 1.8 and −187 ± 18‰ for δ13CH4 and δD-CH4, respectively, and the corresponding values in the summer (June–October) are −65.0 ± 2.5 and −282 ± 25‰. These values indicate predominant CH4emissions from fossil fuel facilities in the winter and wetlands in the summer. It was also found that the shorter-term CH4 variations are more influenced by fossil CH4 than that from wetlands. The finding presumably reflects the fact that the former is released from limited areas such as leakage from fossil fuel facilities, while the latter is released from a vast expanse of wetland. By employing a CH4 emission data set used in an atmospheric chemistry transport model, we calculated seasonal isotopic changes of CH4 sources in western Siberia and compared them to the estimates obtained in this study. The results indicated that the seasonal change in the CH4 emission data set is reasonable, at least in terms of a ratio of fossil to biogenic emissions.

A deep ice core drilled at Dome Fuji, East Antarctica was analyzed for the CO 2 concentration using a wet extraction method in order to reconstruct its atmospheric variations over the past 320 kyr, which includes three full glacial–interglacial climatic cycles, with a mean time resolution of about 1.1 kyr. The CO 2 concentration values derived for the past 65 kyr are very close to those obtained from other Antarctic ice cores using dry extraction methods, although the wet extraction method is generally thought to be inappropriate for the determination of the CO 2 concentration. The comparison between the CO 2 and Ca 2+ concentrations deduced from the Dome Fuji core suggests that calcium carbonate emitted from lands was mostly neutralized in the atmosphere before reaching the central part of Antarctica, or that only a small part of calcium carbonate was involved in CO 2 production during the wet extraction process. The CO 2 concentration for the past 320 kyr deduced from the Dome Fuji core varies between 190 and 300 ppmv, showing clear glacial–interglacial variations similar to the result of the Vostok ice core. However, for some periods, the concentration values of the Dome Fuji core are higher by up to 20 ppmv than those of the Vostok core. There is no clear indication that such differences are related to variations of chemical components of Ca 2+ , microparticle and acidity of the Dome Fuji core. DOI: 10.1034/j.1600-0889.2003.00050.x

Aircraft measurements of atmospheric CO2 concentration over Japan, initiated in January 1979, have been continued to the present. The average seasonal variation of atmospheric CO2 showed maximum concentration early in April and early in May, and minimum concentration in mid-August and mid-September for the lower-most and the upper-most layers of the troposphere, respectively. The peak-to-peak amplitudes of the seasonal variation were 14.5, 9.0 and 7.8 ppmv for the lower, middle and upper tropospheres, respectively. The average rate of annual increase of the C02 concentration over the last 6 years was about 1.3 ppmv yr-1 with considerable variation with time. The vertical profile of the annual mean value of the CO2 concentration was almost the same from year to year; the CO2 concentration decreased gradually with height and the concentration difference between the lowest and highest layers of the troposphere was about 2 ppmv.DOI: 10.1111/j.1600-0889.1987.tb00265.x

[1] To investigate spatial variations of CH4 concentration, δ13CH4, and δD-CH4 over Alaska, aircraft observations were conducted during the summer of 2006. CH4 concentrations elevated above the background level were observed over areas with wetlands and wildfires, important sources of CH4. Several flights showed elevated CH4 values, with corresponding δ13CH4 and δD-CH4 signatures of −63.4‰ ± 3.0‰ and −424‰ ± 79‰, respectively, which are based on the relationship between δ13CH4 (or δD-CH4) and CH4 concentration (single mixing relation), an indication of wetland source. It was also noted that both wetlands and wildfires influenced the CH4 concentrations observed over the wildfire area. Assuming certain emission ratios of CH4 to CO (ERCH4/CO) for the wildfire and certain values of δ13CH4 and δD-CH4 for wetland CH4, we derived δ13CH4 and δD-CH4 of CH4 emitted from the wildfire to be −27.5‰ ± 2.0‰ and −285‰ ± 111‰, respectively, which agreed relatively well with, but was slightly lower than, those obtained by previous studies at lower latitudes. To verify these estimates, bonfire experiments were conducted in the interior of Alaska using the same biomass material burned in the wildfire observed by the aircraft. The result showed that the previously reported ERCH4/CO value was plausible and that δ13CH4 and δD-CH4 obtained by the bonfire experiments agreed with the estimates by the aircraft observations. We also found that δ13CH4 and δD-CH4 values became enriched with increasing combustion efficiency. By using the relationship between δD-CH4 for biomass burning and δD of precipitation, global average of δD-CH4 emitted from biomass burning was estimated to be −204‰ ± 11‰.

[1] Systematic observations of atmospheric carbon monoxide (CO) have been carried out in the western part of the Pacific Ocean since February 1990. The average CO concentration showed a latitudinal gradient, with higher values in the northern hemisphere than in the southern hemisphere. A clear seasonal CO cycle was found nearly at all sampling locations, showing maximum and minimum concentrations in spring and summer, respectively. In the 30°–35°N latitude zone, the average CO concentration was higher and the seasonal amplitude was larger compared with other latitudes. The CO concentration also showed a large interannual variability mainly in association with forest fires. In particular, the forest fires in Siberia in 1998 and Indonesia in 1997–1998 contributed to a remarkable increase in the regional CO concentration, followed by a recovery that took several months to a year. A three-dimensional atmospheric global chemical transport model (CHASER) was used to simulate the observed characteristics of the latitudinal distribution, seasonal cycle, and interannual variability relatively well. Tagged CO experiments with the model revealed that the contribution of CO emissions from various regions in the northern hemisphere to the CO concentrations at our sampling locations varied seasonally in association with Asian outflows and long-range transport from Europe and North America. In the southern hemisphere, biomass burnings significantly affected the regional seasonal CO cycle, in addition to the effect of CO oxidation with OH. It was also found that CHASER underestimates the average CO concentration in the northern hemisphere and its interannual variability.

Measurements of midday vertical atmospheric CO 2 distributions reveal annual-mean vertical CO 2 gradients that are inconsistent with atmospheric models that estimate a large transfer of terrestrial carbon from tropical to northern latitudes. The three models that most closely reproduce the observed annual-mean vertical CO 2 gradients estimate weaker northern uptake of –1.5 petagrams of carbon per year (Pg C year –1 ) and weaker tropical emission of +0.1 Pg C year –1 compared with previous consensus estimates of –2.4 and +1.8 Pg C year –1 , respectively. This suggests that northern terrestrial uptake of industrial CO 2 emissions plays a smaller role than previously thought and that, after subtracting land-use emissions, tropical ecosystems may currently be strong sinks for CO 2 .

[1] Histories of atmospheric N2O concentration and its δ15N and δ18O were reconstructed for the period 1952–2001 on the basis of the analyses of firn air collected at the North Greenland Ice Core Project (NGRIP), Greenland, and Dome Fuji and H72, Antarctica. The N2O concentration increased from 290 ppbv in 1952 to 316 ppbv in 2001, which agrees well with the results from atmospheric observations and polar ice core analyses. The δ15N and δ18O showed a secular decrease, the respective values being 8.9 and 21.5‰ in 1952 and 7.0 and 20.5‰ in 2001. Their rates of change also varied, from about −0.02‰ yr−1 in the 1950s to about −0.04‰ yr−1 in 1960–2001 for δ15N, and from about 0‰ yr−1 to −0.02‰ yr−1 for δ18O. The isotopic budgetary calculations using a two-box model indicated that anthropogenic N2O emission from soils played a main role in the atmospheric N2O increase after industrialization, as well as that the average isotopic ratio of anthropogenic N2O has potentially been changed temporally.

This study assesses polar stratospheric nitrous oxide (N(2)O) and methane (CH(4)) data from the Improved Limb Atmospheric Spectrometer-II (ILAS-II) on board the Advanced Earth Observing Satellite-II (ADEOS-II) retrieved by the Version 1.4 retrieval algorithm. The data were measured between January and October 2003. Vertical profiles of ILAS-II volume mixing ratio (VMR) data are compared with data from two balloon-borne instruments, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-B) and the MkIV instrument, as well as with two satellite sensors, the Odin Sub-Millimetre Radiometer (SMR) for N(2)O and the Halogen Occultation Experiment (HALOE) for CH(4). Relative percentage differences between the ILAS-II and balloon/satellite data and their median values are calculated in 10-ppbv-wide bins for N(2)O (from 0 to 400 ppbv) and in 0.05-ppmv-wide bins for CH(4) (from 0 to 2 ppmv) in order to assess systematic differences between the ILAS-II and balloon/satellite data. According to this study, the characteristics of the ILAS-II Version 1.4 N(2)O and CH(4) data differ between hemispheres. For ILAS-II N(2)O VMR larger than 250 ppbv, the ILAS-II N(2)O agrees with the balloon/SMR N(2)O within +/- 20% in both hemispheres. The ILAS-II N(2)O in the VMR range from 30-50 to 250 ppbv (corresponding to altitudes of similar to 17-30 km in the Northern Hemisphere (NH, mainly outside the polar vortex) and similar to 13-21 km in the Southern Hemisphere (SH, mainly inside the polar vortex) is smaller by similar to 10-30% than the balloon/SMR N(2)O. For ILAS-II N(2)O VMR smaller than 30 ppbv (>similar to 21 km) in the SH, the differences between the ILAS-II and SMR N(2)O are within +/- 10 ppbv. For ILAS-II CH(4) VMR larger than 1 ppmv ( similar to 30 km) and the ILAS-II CH(4) for its VMR smaller than 1 ppmv (>similar to 25 km) only in the NH, are abnormally small compared to the balloon/satellite data.

Systematic observations of the atmospheric CH4 mole fraction and its carbon isotope ratio δ 13 CH 4 have been carried out at Ny Alesund, Svalbard (78°55'N, 11°56'E) since 1991 and 1996, respectively. The CH4 and δ 13 CH 4 showed clear seasonal cycles with respective peak-to-peak amplitudes of 48 ppb and 0.42%o. By comparing the anomalies in the increase rate of the CH4 with those of δ 13 CH 4, it is suggested that the cause of the rapid increase in the CH4 mole fraction observed at Ny Alesund in 1998 could be attributable to an enhanced CH 4 release from wetland and biomass burning.

The long-term changes of the stratospheric mixing ratio of CH4 over the period of 1978-2003 are derived from balloon-borne data of H-2, CH4 and N2O. The data were obtained by collecting whole air samples and subsequent gas chromatographic analyses. To eliminate the short-term variability attributed to dynamical processes, the N2O mixing ratio is used as a proxy for altitude. A correlation analysis for the individual years is applied and the CH4 mixing ratios are interpolated to four different levels of N2O, corresponding to altitudes of approximately 17, 23, 26 and 30 km at midlatitudes. For the investigated period of 1978 to 2003 we find increases at the four levels of 207 +/- 32 ppb, 159 +/- 21 ppb, 140 +/- 34 ppb and 111 +/- 60 ppb, respectively. The CH4 trend has slowed down in recent years and is best fitted by a second-order polynomial. The increase of CH4 can account for only 25-34% of the increase in stratospheric H2O of 1%/yr over the last decades as derived from previous studies. The simultaneously measured time series of stratospheric H-2 mixing ratios shows that the contribution of stratospheric H-2 to the H2O trend in the period 1988-2003 is minor.

[1] Vertical profiles of nitrous oxide and methane at high latitudes (57–72°N; 64–89°S) were observed by the Improved Limb Atmospheric Spectrometer (ILAS) solar occultation sensor aboard Advanced Earth Observing Satellite. These measurements were made continuously from November 1996 through June 1997 with some additional periods in September–October 1996. A validation study of the nitrous oxide and methane data processed with the Version 5.20 ILAS retrieval algorithm is presented in this paper. Comparisons are made with (1) nitrous oxide and methane obtained by the ILAS validation balloon campaigns at Kiruna, Sweden, and at Fairbanks, Alaska, in the Arctic; (2) nitrous oxide and methane by the Photochemistry of Ozone Loss in the Arctic Region in Summer aircraft campaign in the Arctic; (3) nitrous oxide by the ground-based spectroscopic measurements and by the aircraft-based remote sensing measurements in the Arctic; and (4) methane by satellite measurements of the Version 19 Halogen Occultation Experiment in the Arctic and Antarctic. Comparisons of ILAS nitrous oxide and methane with Upper Atmosphere Research Satellite Reference Atmosphere data are also made. The results of the comparisons and additional ILAS internal consistency analyses are as follows: (1) the uncertainty of ILAS nitrous oxide is better than 10% over 10–30 km in altitude, and is larger than 50% over 30–40 km, which is comparable to the expected total errors of the ILAS measurements; (2) the uncertainty of ILAS methane is better than 10% over 10–50 km, except for 15–30 km in winter with positive biases exceeding 20%, which is smaller than or comparable to the expected total errors of the ILAS measurements (the quality of ILAS methane in the polar lower stratosphere is better in summer than in winter). In summary, the characteristics of ILAS measurements, i.e., high sampling frequency in polar latitudes with high vertical resolution, along with the good quality of ILAS Version 5.20 nitrous oxide for 10–40 km and the good quality of ILAS Version 5.20 methane for 10–50 km except for 15–30 km in winter, make the ILAS nitrous oxide and methane data set valuable for scientific study of various polar stratospheric phenomena.

We present observations of CH 4 concentrations from the lower to upper troposphere (LT and UT) over Japan during 1988–2010 based on aircraft measurements from the Tohoku University (TU). The analysis is aided by simulation results using an atmospheric chemistry transport model (i.e. ACTM). Tropospheric CH 4 over Japan shows interannual and seasonal variations that are dependent on altitudes, primarily reflecting differences in air mass origins at different altitudes. The long-term trend and interannual variation of CH 4 in the LT are consistent with previous reports of measurements at surface baseline stations in the northern hemisphere. However, those in the UT show slightly different features from those in the LT. In the UT, CH 4 concentrations show a seasonal maximum in August due to efficient transport of air masses influenced by continental CH 4 sources, while LT CH 4 reaches its seasonal minimum during summer due to enhanced chemical loss. Vertical profiles of the CH 4 concentrations also vary with season, reflecting the seasonal cycles at the respective altitudes. In summer, transport of CH 4 -rich air from Asian regions elevates UT CH 4 levels, forming a uniform vertical profile above the mid-troposphere. On the other hand, CH 4 decreases nearly monotonically with altitude in winter–spring. The ACTM simulations with different emission scenarios reproduce general features of the tropospheric CH 4 variations over Japan. Tagged tracer simulations using the ACTM indicate substantial contributions of CH 4 sources in South Asia and East Asia to the summertime high CH 4 values observed in the UT. This suggests that our observations over Japan are highly sensitive to CH 4 emission signals particularly from Asia. Keywords: methane, aircraft observation, long-term variation, seasonality, vertical profile, Asian outflow, atmospheric chemistry transport model (Published: 22 May 2014) Citation: Tellus B 2014, 66 , 23837, http://dx.doi.org/10.3402/tellusb.v66.23837 To access the supplementary material to this article, please see Supplementary files under Article Tools online.

Detailed observations of O 2 :CO 2 exchange ratios were conducted in a cool temperate deciduous forest located in central Japan. The exchange ratios of soil respiration and net assimilation were found to be 1.11±0.01 and 1.02±0.03 from soil chamber and branch bag measurements, respectively. Continuous measurements of the atmospheric O 2 /N 2 ratio and the CO 2 concentration, made inside the canopy during a summer season, indicated that the average exchange ratio was lower in the daytime (0.87±0.02) than in the nighttime (1.03±0.02) with a daily mean value of 0.94±0.01. The observed average daytime and nighttime exchange ratios were nearly consistent with the corresponding values obtained from a one-box canopy O 2 /CO 2 budget model simulation of net turbulent O 2 and CO 2 fluxes between the atmosphere and the forest ecosystem. Our results suggest that the daily mean exchange ratios of the net turbulent O 2 and CO 2 fluxes depend sensitively on the forest ecosystem processes. Keywords: O 2 :CO 2 exchange ratio, forest ecosystem, atmospheric O 2 /N 2 ratio, continuous measurements (Published: 4 December 2013) Citation: Tellus B 2013, 65 , 21120, http://dx.doi.org/10.3402/tellusb.v65i0.21120

We present analysis of the temporal variation of atmospheric CO 2 in the subtropical region of East Asia, obtained aboard a ferry between Ishigaki Island and Hateruma Island, Japan for the period June 1993–April 2005. The annual mean CO 2 concentration increases from 360.1 ppmv in 1994 to 378.4 ppmv in 2004, showing an average growth rate of 1.8 ppmv yr -1 . The growth rate shows interannual variations with high values during ENSO events. The average seasonal CO 2 cycle reaches the maximum in early April and the minimum in mid-September, with a peak-to-peak amplitude of 8.5 ppmv. Numerical simulations using a three-dimensional atmospheric transport model show interannual variations of the CO 2 growth rate similar to the observation, but the amplitude of the seasonal cycle is larger, with maximum concentration appearing earlier than the observation by 1 month. Low CO 2 values observed during the spring of 1998 are likely associated with the 1997/1998 ENSO event. A backward trajectory analysis suggests that they were due to changes in atmospheric transport whereby maritime air masses from the Pacific Ocean dominated over polluted air masses from the Asian Continent. Extreme values (either high or low) of CO 2 are also occasionally observed. A comparison of backward trajectories of air parcels with CO 2 concentration fields calculated using the atmospheric transport model shows that these unusual CO 2 concentrations result from the transport of air affected not only by anthropogenic CO 2 emissions but also by terrestrial biospheric activities mainly in China. DOI: 10.1111/j.1600-0889.2007.00288.x

Systematic and continuous measurements of the atmospheric CO 2 concentration have been carried out at Syowa Station, Antarctica since February 1984. The measurement system was renewed in 1995, but the continuity of the data from the two systems was confirmed by operating them simultaneously. The CO 2 data taken for 17 years from 1984 to 2000 showed clear evidence for a seasonal cycle, a secular trend and interannual variations. The seasonal cycle was variable from year to year, with especially larger amplitudes in 1992 and 1998 and a large phase delay in 1993. A rapid increase in the CO 2 concentration was observed in 1987, 1994 and 1998 in association with ENSO events. The average rate of the secular CO 2 increase for the last 17 years was calculated to be 1.49 ppmv yr −1 . Short-term CO 2 variations with amplitudes of around 1.0 ppmv were found in the austral summer season of several years after 1990, probably due to an intrusion of CO 2 -depleted air mass into the Antarctic region. DOI: 10.1034/j.1600-0889.2003.01471.x

Using discrete air sampling, values of δ 13 C and δ 18 O in atmospheric CO 2 , as well as its concentration, were measured in a forest in the central part of the main island of Japan during the period from June 1994 to June 1996 to examine the biospheric contribution to their temporal variations. δ 13 C shows a prominent diurnal variation with high values in the daytime and low values in the nighttime, especially during the warm season. δ 13 C also vary seasonally, showing a maximum in summer and a minimum in spring. The diurnal and seasonal variations of δ 13 C are opposite in phase with those of the CO 2 concentration. The rate of change in δ 13 C with respect to the CO 2 concentration is found to be approximately -0.05‰/ppmv. This suggests that the diurnal and seasonal variations of the CO 2 concentration are produced primarily by diurnally- and seasonally-dependent photosynthetic-respiratory processes of the biosphere near the observation site, respectively. In the warm season, δ 18 O also increases in the daytime and decreased in the nighttime, which is similar to the diurnal variation of δ 13 C, but opposite to that of the CO 2 concentration. The diurnal δ 18 O variation is thought to be caused by the release of isotopically heavy CO 2 during photosynthesis, and light CO 2 during respiration. However, an interpretation of the seasonal δ 18 O variation is found to be much more difficult than those of δ 13 C and the CO 2 concentration. This is likely due to complicated combinations of different seasonally varying fluxes of biospheric CO 2 into the atmosphere, as well as to various weather-dependent factors governing the δ 18 O composition in CO 2 . DOI: 10.1034/j.1600-0889.49.issue4.3.x

Stratospheric air samples were collected over Japan on August 31, 1994 using a balloon-borne cryogenic sampler and then analyzed for the CH4 concentration and δ13C in CH4. The δ13C value increased from about −47.5‰ at the tropopause to about −38.9‰ at 34.7 km, accompanied by a rapid decrease of the CH4 concentration with height. From the measured values of the CH4 concentration and δ13C, the apparent carbon isotopic fractionation factor was estimated to be 1.0131±0.0006. The contributions of the chemical CH4 reactions with OH, O(¹D) and Cl were also examined by using an one-dimensional photochemical-diffusion model. It is suggested from this examination that the reaction of CH4 with Cl is especially important for δ13C in the stratosphere.