scholarly journals Long-term observation of mass-independent oxygen isotope anomaly in stratospheric CO<sub>2</sub>

2008 ◽  
Vol 8 (20) ◽  
pp. 6189-6197 ◽  
Author(s):  
S. Kawagucci ◽  
U. Tsunogai ◽  
S. Kudo ◽  
F. Nakagawa ◽  
H. Honda ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Middle Atmosphere ◽  
Isotope Composition ◽  
Mixing Ratio ◽  
Least Squares Regression ◽  
Air Samples ◽  
Mixing Ratios ◽  
Long Term Observation ◽  
Isotope Correlation ◽  
Middle Stratosphere

Abstract. Stratospheric and upper tropospheric air samples were collected during 1994–2004 over Sanriku, Japan and in 1997 over Kiruna, Sweden. Using these archived air samples, we determined the triple oxygen-isotope composition of stratospheric CO2 and the N2O mixing ratio. The maximum Δ17OCO2 value of +12.2‰, resembling that observed previously in the mesosphere at 60 km height, was found in the middle stratosphere over Kiruna at 25.6 km height, suggesting that upper stratospheric and mesospheric air descended to the middle stratosphere through strong downward advection. A least-squares regression analysis of our observations on a δ18OCO2−δ17OCO2 plot (r2>0.95) shows a slope of 1.63±pm0.10, which is similar to the reported value of 1.71±0.06, thereby confirming the linearity of three isotope correlation with the slope of 1.6–1.7 in the mid-latitude lower and middle stratosphere. The slope decrease with increasing altitude and a curvy trend in three-isotope correlation reported from previous studies were not statistically significant. Using negative linear correlations of Δ17OCO2 and δ18OCO2 with the N2O mixing ratio, we quantified triple oxygen-isotope fluxes of CO2 to the troposphere as +48‰ GtC/yr (Δ17OCO2) and +38‰ GtC/yr (δ18OCO2) with ~30% uncertainty. Comparing recent model results and observations, underestimation of the three isotope slope and the maximum Δ17OCO2 value in the model were clarified, suggesting a smaller O2 photolysis contribution than that of the model. Simultaneous observations of δ18OCO2, δ17OCO2, and N2O mixing ratios can elucidate triple oxygen isotopes in CO2 and clarify complex interactions among physical, chemical, and photochemical processes occurring in the middle atmosphere.

scholarly journals Long-term observation of mass-independent oxygen isotope anomaly in stratospheric CO<sub>2</sub>

2007 ◽  
Vol 7 (6) ◽  
pp. 15723-15737
Author(s):  
S. Kawagucci ◽  
U. Tsunogai ◽  
S. Kudo ◽  
F. Nakagawa ◽  
H. Honda ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Middle Atmosphere ◽  
Least Squares Regression ◽  
Model Calculations ◽  
Air Samples ◽  
Oxygen Isotopic ◽  
Long Term Observation ◽  
Open Question ◽  
Division 2

Abstract. Anomalous oxygen isotopic compositions of stratospheric CO2 were first reported in 1989, although their detailed behavior in the middle atmosphere is still open question. We collected 60 stratospheric air samples over Sanriku, Japan from 1991 to 2004 and Kiruna, Sweden in 1997. Using these accumulated air samples, we performed long-term observations of triple oxygen isotope compositions of stratospheric CO2. It is the first simultaneous observation in the stratosphere of both relations between Δ17OCO2 and [N2O], and δ18OCO2 and δ17OCO2, accurately. Observations confirmed simultaneous linear correlations between δ18OCO2, Δ17OCO2, and [N2O] within [N2O]>50 ppbv: the correlations faded away along with decreasing [N2O] from 50 ppbv. For dividing observation results by [N2O]=50 ppbv, the divided datasets show that 1) both Δ17OCO2 and δ18OCO2 are conservative parameters within the N2O-rich division, 2) the slope of least squares regression on δ18O–δ17O plot for the N2O-rich division is significantly steeper than that of the N2O-depleted one, and 3) the N2O-depleted division shows a discrepancy with recent model calculations, suggesting unconsidered isotope fractionation processes on complicated oxygen interactions in the CO2-O3-O2 system in the upper stratosphere and mesosphere.

scholarly journals Validation of Aura MLS retrievals of temperature, water vapour and ozone in the upper troposphere and lower–middle stratosphere over the Tibetan Plateau during boreal summer

2016 ◽  
Author(s):  
X. L. Yan ◽  
J. S. Wright ◽  
X. D. Zheng ◽  
N. Livesey ◽  
H. Vömel ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Water Vapour ◽  
Boreal Summer ◽  
The Tibetan Plateau ◽  
Mixing Ratio ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Dry Bias ◽  
Temperature Water ◽  
Middle Stratosphere

Abstract. We validate Aura Microwave Limb Sounder (MLS) version 3 (v3) and version 4 (v4) retrievals of summertime temperature, water vapour and ozone in the upper troposphere and lower–middle stratosphere (UTLS; 10–316 hPa) against balloon soundings collected during the Study of Ozone, Aerosols and Radiation over the Tibetan Plateau (SOAR-TP). Mean v3 and v4 profiles of temperature, water vapour and ozone in this region during the measurement campaigns are almost identical through most of the stratosphere (10–68 hPa), but differ in several respects in the upper troposphere and tropopause layer. Differences in v4 relative to v3 include slightly colder mean temperatures from 100–316 hPa, smaller mean water vapour mixing ratios in the upper troposphere (215–316 hPa), and a more vertically homogeneous profile of mean ozone mixing ratios below the climatological tropopause (100–316 hPa). These changes substantially improve agreement between ozonesondes and MLS ozone retrievals in the upper troposphere, but slightly worsen existing cold and dry biases in the upper troposphere. Aura MLS v3 and v4 temperature profiles contain significant cold biases relative to collocated temperature measurements in several layers of the lower–middle stratosphere (mean biases of −1.3 to −1.8 K centered at 10–12 hPa, 26–32 hPa and 68– 83 hPa) and in the upper troposphere (mean biases of approximately −2.3±0.3 K in v3 and −2.6±0.4 K in v4 between 147 and 261 hPa). MLS v3 and v4 profiles of water vapour volume mixing ratio generally compare well with collocated measurements, with a slight dry bias (v4: −8±4%) near 22–26 hPa, a slight wet bias (v4: +12±5%) near 68–83 hPa, and a more substantial dry bias (v4: −32±11%) in the upper troposphere (121–261 hPa). MLS v3 and v4 retrievals of ozone volume mixing ratio are biased high relative to collocated ozonesondes through most of the stratosphere (18–83 hPa), but are biased low at 100 hPa. The largest positive biases in ozone retrievals are located at 83 hPa (approximately +70%); this peak was not identified by earlier validations and may be regionally or seasonally specific. Ozone retrievals are substantially improved in v4 relative to v3, with smaller biases in the tropopause layer, reduced variance below 68 hPa, larger data yields, and smoother gradients in the vertical profile of ozone biases in the upper troposphere.

scholarly journals Correcting the impact of the isotope composition on the mixing ratio dependency of water vapour isotope measurements with cavity ring-down spectrometers

2020 ◽  
Vol 13 (6) ◽  
pp. 3167-3190
Author(s):  
Yongbiao Weng ◽  
Alexandra Touzeau ◽  
Harald Sodemann
Keyword(s):  
Water Vapour ◽  
Isotope Composition ◽  
Data Interpretation ◽  
Polar Regions ◽  
Mixing Ratio ◽  
Mixing Ratios ◽  
Δ18o And Δd ◽  
Isotope Composition Of Water ◽  
The Impact ◽  
Cavity Ring Down

Abstract. Recent advances in laser spectroscopy enable high-frequency in situ measurements of the isotope composition of water vapour. At low water vapour mixing ratios, however, the measured stable water isotope composition can be substantially affected by a measurement artefact known as the mixing ratio dependency, which is commonly considered independent of the isotope composition. Here we systematically investigate how the mixing ratio dependency, in a range from 500 to 23 000 ppmv of three commercial cavity ring-down spectrometers, is affected by the isotope composition of water vapour. We find that the isotope composition of water vapour has a substantial and systematic impact on the mixing ratio dependency for all three analysers, particularly at mixing ratios below 4000 ppmv. This isotope composition dependency can create a deviation of ±0.5 ‰ and ±6.0 ‰ for δ18O and δD, respectively, at ∼2000 ppmv, resulting in about 2 ‰–3 ‰ deviation for the d-excess. An assessment of the robustness of our findings shows that the overall behaviour is reproducible over up to 2 years for different dry gas supplies, while being independent of the method for generating the water vapour and being the first order of the evaluation sequence. We propose replacing the univariate mixing ratio dependency corrections with a new, combined isotope composition–mixing ratio dependency correction. Using aircraft- and ship-based measurements in an Arctic environment, we illustrate a relevant application of the correction. Based on our findings, we suggest that the dependency on the isotope composition may be primarily related to spectroscopy. Repeatedly characterising the combined isotope composition–mixing ratio dependency of laser spectrometers when performing water vapour measurements at high elevations, on aircraft, or in polar regions appears critical to enable reliable data interpretation in dry environments.

scholarly journals Methane as a diagnostic tracer of changes in the Brewer–Dobson circulation of the stratosphere

2015 ◽  
Vol 15 (7) ◽  
pp. 3739-3754 ◽  
Author(s):  
E. E. Remsberg
Keyword(s):  
Time Series ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Lower Stratosphere ◽  
Middle Atmosphere ◽  
Wave Activity ◽  
Mixing Ratio ◽  
Use Of Time ◽  
Wave Induced ◽  
Middle Stratosphere

Abstract. This study makes use of time series of methane (CH4) data from the Halogen Occultation Experiment (HALOE) to detect whether there were any statistically significant changes of the Brewer–Dobson circulation (BDC) within the stratosphere during 1992–2005. The HALOE CH4 profiles are in terms of mixing ratio versus pressure altitude and are binned into latitude zones within the Southern Hemisphere and the Northern Hemisphere. Their separate time series are then analyzed using multiple linear regression (MLR) techniques. The CH4 trend terms for the Northern Hemisphere are significant and positive at 10° N from 50 to 7 hPa and larger than the tropospheric CH4 trends of about 3% decade−1 from 20 to 7 hPa. At 60° N the trends are clearly negative from 20 to 7 hPa. Their combined trends indicate an acceleration of the BDC in the middle stratosphere of the Northern Hemisphere during those years, most likely due to changes from the effects of wave activity. No similar significant BDC acceleration is found for the Southern Hemisphere. Trends from HALOE H2O are analyzed for consistency. Their mutual trends with CH4 are anti-correlated qualitatively in the middle and upper stratosphere, where CH4 is chemically oxidized to H2O. Conversely, their mutual trends in the lower stratosphere are dominated by their trends upon entry to the tropical stratosphere. Time series residuals for CH4 in the lower mesosphere also exhibit structures that are anti-correlated in some instances with those of the tracer-like species HCl. Their occasional aperiodic structures indicate the effects of transport following episodic, wintertime wave activity. It is concluded that observed multi-year, zonally averaged distributions of CH4 can be used to diagnose major instances of wave-induced transport in the middle atmosphere and to detect changes in the stratospheric BDC.

scholarly journals Extreme <sup>13</sup>C depletion of CCl<sub>2</sub>F<sub>2</sub> in firn air samples from NEEM, Greenland

2012 ◽  
Vol 12 (7) ◽  
pp. 18499-18530
Author(s):  
A. Zuiderweg ◽  
R. Holzinger ◽  
P. Martinerie ◽  
R. Schneider ◽  
J. Kaiser ◽  
...  
Keyword(s):  
Mass Balance ◽  
Carbon Isotope ◽  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Isotopic Fractionation ◽  
Large Change ◽  
High Volume ◽  
Mixing Ratio ◽  
Stable Carbon ◽  
Air Samples

Abstract. A series of 12 high volume air samples collected from the S2 firn core during the North Greenland Eemian Ice Drilling (NEEM) 2009 campaign have been measured for mixing ratio and stable carbon isotope composition of the chlorofluorocarbon CFC-12 (CCl2F2). While the mixing ratio measurements compare favorably to other firn air studies, the isotope results show extreme 13C depletion at the deepest measurable depth (65 m), to values lower than δ13C = −80‰ vs. VPDB (the international stable carbon isotope scale), compared to present day surface tropospheric measurements near −40‰. Firn air modeling was used to interpret these measurements. Reconstructed atmospheric time series indicate even larger depletions (to −120‰) near 1950 AD, with subsequent rapid enrichment of the atmospheric reservoir of the compound to the present day value. Mass-balance calculations show that this change must have been caused by a large change in the isotopic composition of anthropogenic CFC-12 emissions, probably due to technological changes in the CFC production process over the last 80 yr. Propagating the mass-balance calculations into the future demonstrates that as emissions decrease to zero, isotopic fractionation by the stratospheric sinks will lead to continued 13C enrichment in atmospheric CFC-12.

scholarly journals Vertical distributions of N<sub>2</sub>O isotopocules in the equatorial stratosphere

2017 ◽  
Author(s):  
Sakae Toyoda ◽  
Naohiro Yoshida ◽  
Shinji Morimoto ◽  
Shuji Aoki ◽  
Takakiyo Nakazawa ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Vertical Gradient ◽  
Enrichment Factors ◽  
Equatorial Pacific ◽  
Vertical Profiles ◽  
Mixing Ratio ◽  
Air Samples ◽  
Eastern Equatorial Pacific ◽  
Vertical Distributions ◽  
Middle Stratosphere

Abstract. Vertical profiles of nitrous oxide (N2O) and its isotopocules, isotopically substituted molecules, were obtained over the equator at altitudes of 16–30 km. Whole air samples were collected using newly developed balloon-borne compact cryogenic samplers over the Eastern Equatorial Pacific in 2012 and Biak Island, Indonesia in 2015. They were examined in the laboratory using gas chromatography and mass spectrometry. The mixing ratio and isotopocule ratios of N2O in the equatorial stratosphere showed a weaker vertical gradient than the previously reported profiles in the subtropical and mid-latitude and high-latitude stratosphere. From the relation between the mixing ratio and isotopocule ratios, further distinct characteristics were found over the equator: (1) Observed isotopocule enrichment factors (&amp;varepsilon; values) in the middle stratosphere (25–30 km) are almost equal to &amp;varepsilon; values reported from broadband photolysis experiments conducted in the laboratory. (2) &amp;varepsilon; values in the lower stratosphere (

scholarly journals Validation of Aura MLS retrievals of temperature, water vapour and ozone in the upper troposphere and lower–middle stratosphere over the Tibetan Plateau during boreal summer

2016 ◽  
Vol 9 (8) ◽  
pp. 3547-3566 ◽  
Author(s):  
Xiaolu Yan ◽  
Jonathon S. Wright ◽  
Xiangdong Zheng ◽  
Nathaniel J. Livesey ◽  
Holger Vömel ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Water Vapour ◽  
Boreal Summer ◽  
The Tibetan Plateau ◽  
Mixing Ratio ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Temperature Water ◽  
Middle Stratosphere

Abstract. We validate Aura Microwave Limb Sounder (MLS) version 3 (v3) and version 4 (v4) retrievals of summertime temperature, water vapour and ozone in the upper troposphere and lower–middle stratosphere (UTLS; 10–316 hPa) against balloon soundings collected during the Study of Ozone, Aerosols and Radiation over the Tibetan Plateau (SOAR-TP). Mean v3 and v4 profiles of temperature, water vapour and ozone in this region during the measurement campaigns are almost identical through most of the stratosphere (10–68 hPa), but differ in several respects in the upper troposphere and tropopause layer. Differences in v4 relative to v3 include slightly colder mean temperatures from 100 to 316 hPa, smaller mean water vapour mixing ratios in the upper troposphere (215–316 hPa) and a more vertically homogeneous profile of mean ozone mixing ratios below the climatological tropopause (100–316 hPa). These changes substantially improve agreement between ozonesondes and MLS ozone retrievals in the upper troposphere, but slightly worsen existing cold and dry biases at these levels. Aura MLS temperature profiles contain significant cold biases relative to collocated temperature measurements in several layers of the lower–middle stratosphere and in the upper troposphere. MLS retrievals of water vapour volume mixing ratio generally compare well with collocated measurements, excepting a substantial dry bias (−32 ± 11 % in v4) that extends through most of the upper troposphere (121–261 hPa). MLS retrievals of ozone volume mixing ratio are biased high relative to collocated ozonesondes in the stratosphere (18–83 hPa), but are biased low at 100 hPa. The largest relative biases in ozone retrievals (approximately +70 %) are located at 83 hPa. MLS v4 offers substantial benefits relative to v3, particularly with respect to water vapour and ozone. Key improvements include larger data yields, reduced noise in the upper troposphere and smaller fluctuations in the bias profile at pressures larger than 100 hPa. The situation for temperature is less clear, with cold biases and noise levels in the upper troposphere, both larger in v4 than in v3. Several aspects of our results differ from those of validations conducted in other locations. These differences are often amplified by monsoon onset, indicating that the Asian monsoon anticyclone poses unique challenges for remote sensing that impact the quality of MLS retrievals in this region.

scholarly journals Extreme <sup>13</sup>C depletion of CCl<sub>2</sub>F<sub>2</sub> in firn air samples from NEEM, Greenland

2013 ◽  
Vol 13 (2) ◽  
pp. 599-609 ◽  
Author(s):  
A. Zuiderweg ◽  
R. Holzinger ◽  
P. Martinerie ◽  
R. Schneider ◽  
J. Kaiser ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Large Change ◽  
High Volume ◽  
Mixing Ratio ◽  
Stable Carbon ◽  
Air Samples ◽  
The North ◽  
Technological Advances

Abstract. A series of 12 high volume air samples collected from the S2 firn core during the North Greenland Eemian Ice Drilling (NEEM) 2009 campaign have been measured for mixing ratio and stable carbon isotope composition of the chlorofluorocarbon CFC-12 (CCl2F2). While the mixing ratio measurements compare favorably to other firn air studies, the isotope results show extreme 13C depletion at the deepest measurable depth (65 m), to values lower than δ13C = −80‰ vs. VPDB (the international stable carbon isotope scale), compared to present day surface tropospheric measurements near −40‰. Firn air modeling was used to interpret these measurements. Reconstructed atmospheric time series indicate even larger depletions (to −120‰) near 1950 AD, with subsequent rapid enrichment of the atmospheric reservoir of the compound to the present day value. Mass-balance calculations show that this change is likely to have been caused by a large change in the isotopic composition of anthropogenic CFC-12 emissions, probably due to technological advances in the CFC production process over the last 80 yr, though direct evidence is lacking.

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