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The seasonal variations of greenhouse gases at about 11 km altitude were analyzed from monthly air samples collected aboard a commercial airliner flying between Europe and Japan from April 2012 to March 2014. Compared to lower latitudes, the upper troposphere between 50 and 70°N showed higher CH4 and SF6 and an earlier seasonal phase of CO2. However, N2O values were similar to those in the subtropics. CH4, N2O, and SF6 in the lower stratosphere with potential temperature of up to 50 K above the tropopause showed seasonal variations with maxima in November/December and minima in April/May. At potential temperatures of 37.5–50 K above the tropopause, SF6 age was estimated to be about 22 months in May and 9 months in November. This strong seasonal variation is explained by the subsidence of high-stratospheric air in spring and the effective flushing of the lowermost stratospheric air with tropospheric air in autumn.

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.

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.

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.

[1] We examined pCO2air and pCO2sea observed in the eastern Indian sector of the Southern Ocean (south of 50°S, 140°–150°E) during austral spring-summer from November 2001 to March 2002 using 4 research vessels. pCO2sea changed by as much as 200 μatm over the 5-month period in the Seasonal Sea Ice Zone (SSIZ), due mostly to very low values in January caused by stratification of water column and strong biological activity. In the SSIZ, the air-sea CO2 flux showed large temporal variations, from −2.9 g m−2 month−1 in January 2002 to −0.65 g m−2 month−1 in February 2002. The monthly oceanic CO2 uptake in the area covered by this study (1.5 × 1012 km2) was estimated to be in a range of 1.0 × 10−3 to 1.7 × 10−3 PgC month−1, with a mean value of 1.3 × 10−3 PgC month−1.

[1] To investigate the gravitational separation of atmospheric components in the stratosphere, air samples collected over Japan, the Arctic and the Antarctic were analyzed for δ15N of N2 and δ18O of O2. The gravitational separation is a function of latitude, showing the largest effect inside the polar vortex over the Arctic. The relationship between the gravitational separation (calculated using a steady-state 1-dimensional eddy-diffusion/molecular-diffusion model) and the CO2 age (calculated using a 1-dimensional time dependent eddy-diffusion model) suggests that the observed gravitational separation is fundamentally a result of diffusive separation but modified by meridional circulation of air in the stratosphere. We also obtain a compact relationship between the gravitational separation and the N2O concentration. By comparing the gravitational separations at two height intervals with the N2O concentrations >125 ppb and

[1] Lower stratospheric O2/N2 ratios (δ(O2/N2)) at northern middle and high latitudes were measured by analyzing aircraft air samples collected between Nagoya, Japan and Svalbard Islands in the Arctic during the early spring of 2002. The measured values of δ(O2/N2) are relatively uniform horizontally in the lowermost part of the stratosphere but increase with height. Vertical distributions of δ(O2/N2) and the CO2 concentration observed over Svalbard Islands and Barrow, Alaska are negatively correlated. By examining the rates of change in δ(O2/N2) and δ13C of CO2 relative to the CO2 concentration, such a correlation observed is mainly attributable to upward propagation of their seasonal cycles produced on the ground surface for the troposphere and height-dependent air age for the stratosphere. However, from the vertical profiles of δ15N of N2, δ18O of O2 and δ(Ar/N2) measured in the lowermost part of the stratosphere over Svalbard Islands, it is suggested that the relationship between δ(O2/N2) and the CO2 concentration is affected by the gravitational separation. By correcting the measured δ(O2/N2) and δ13C values for this gravitational separation, the relationships of δ(O2/N2) and δ13C with the CO2 concentration are consistent with those expected from their secular trends in the troposphere.

[1] Methyl chloride (CH3Cl) concentration was measured in air trapped in a deep ice core from Dome Fuji, Antarctica covering the last glacial–present interglacial (Holocene) change. The record shows that the CH3Cl concentration was relatively constant, being similar to the present levels, during the pre-industrial Holocene. In contrast, the CH3Cl concentration was significantly high and variable in the last glacial period, possibly due to impurity-related production of CH3Cl in ice sheet. Under the assumption that the production was the sole cause of the excess CH3Cl, the atmospheric CH3Cl concentration during the last glacial was estimated using simultaneously measured calcium data for the ice core to have been enhanced by 30% compared with the pre-industrial Holocene concentration. Because the major sink of CH3Cl was stronger during the last glacial than during the Holocene, the enhancement of CH3Cl during the last glacial was likely due to the glacial period source being enhanced.

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.

[1] To examine the spatial and temporal behavior of stratospheric O2, air samples were collected using a cryogenic sampler over Sanriku, Japan and Syowa, Antarctica and analyzed for δ(O2/N2), δ15N of N2 and δ18O of O2. The measured values of all these components decreased gradually with height. The differences in δ(O2/N2), δ15N and δ18O between the middle and lowermost levels of the stratosphere were about 250, 100, and 180 per meg, respectively. The observed stratospheric profiles of δ15N and δ18O were in agreement with those calculated using a steady-state 1-dimensional eddy-diffusion/molecular-diffusion model, which suggests that the upward decrease of stratospheric δ(O2/N2) is caused by a gravitational separation of O2 and N2 molecules. The averaged stratospheric δ(O2/N2) at heights above 20–25 km over Sanriku, corrected for the gravitational separation, was always higher than the upper tropospheric δ(O2/N2) value over Japan, and it decreased secularly. From the past temporal δ(O2/N2) variation deduced from the gravitational separation-corrected stratospheric δ(O2/N2) values and the mean ages of the respective air samples, which corresponds to its secular trend in the troposphere, average terrestrial biospheric and oceanic CO2 uptake for October 1993–September 2001 were estimated to be 1.1 ± 1.3 and 1.8 ± 1.3 GtC yr−1, respectively.