Trends in stratospheric concentrations of trace gases in the Northern Hemisphere during the years 1974–1979

Absorption by sulfur hexafluoride (SF6) has been detected in high‐resolution infrared solar spectra of the lower stratosphere and upper troposphere. The identification is based on measurements of the intense, unresolved ν3 band Q branch at 947.9 cm−1 in solar occultation spectra recorded near 31°N and 47°S latitude by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer on April 30 to May 1, 1985, during the Spacelab 3 shuttle mission. Vertical SF6 volume mixing ratio profiles have been retrieved using an onion‐peeling nonlinear least squares spectral fitting procedure with SF6 line‐by‐line Spectroscopic parameters generated recently by Bobin and coworkers from their analysis of the SF6 ν3 band. Between 12 and 18 km altitude, the region over which the retrievals are most accurate (about ±26% one sigma), the SF6 volume mixing ratio is independent of altitude with an average measured value of 1.42 parts per trillion by volume (pptv) at 31°N latitude. There is evidence for a decline in the SF6 volume mixing ratio with increasing altitude between 18 and 22 km, but the results are not conclusive because of the weakness of the absorption. Absorption by the SF6 Q branch is below the noise level of the spectra at tangent heights above ∼22 km. The measurements are compared with previously reported values and discussed in terms of the atmospheric lifetime of SF6, the long‐term trend of atmospheric SF6, and the possible role of SF6 as an atmospheric greenhouse gas.

Section: The Comparison Between the April 1975 Air Sampling And The Amentioning

confidence: 76%

Infrared spectroscopic detection of sulfur hexafluoride (sf₆) in the lower stratosphere and upper troposphere

Rinsland

Brown²,

Farmer

1990

“…Because of the transition from the P-System to CLASS in October 1981, samples from latitudes below 25 ø were not available for COS analyses. As has been discussed in previous papers [Leifer et al, 1982[Leifer et al, , 1984, the drawn isopleth lines follow the general slope of the tropopause. tions during April 1982 showed no abnormal behavior on either the previous or succeeding missions.…”

Section: Introductionmentioning

confidence: 99%

“…If there was some dilution mechanism lowering the concentrations in the sampling bottles, then the CO2 concentrations should have reflected this change. E1 Chich6n erupted just prior to the April 1982 mission and injected significant quantities of gases and aerosol into the stratosphere [Krueger, 1983;Leifer et al, 1984;Mroz et al, 1983;Robock and Matson, 1983]. The plume from this eruption was detected in the equatorial region during the April 20 and 21, 1982, flights.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Project Airstream: COS measurements in the stratosphere and troposphere

Leifer¹

1989

Stratospheric and tropospheric gas samples were collected and subsequently analyzed for COS under the Department of Energy's High‐Altitude Sampling Program (HASP) during the years 1980–1983. The northern hemisphere stratospheric inventories during these years ranged from 0.24 to 0.29 Tg. Coefficients for a least squares exponential fit were obtained for seasonal and latitudinal data subsets and showed profiles similar to previously published models. The HASP data base, when compared to these models, supports the concept of a low OH concentration profile in the lower stratosphere. Summer mixing ratios were elevated at all altitudes, indicating the need for model refinements to account for the seasonal difference. The results of the tropospheric samples analyzed suggest a decreasing COS mixing ratio with altitude.

“…Assuming this equation, a fit to the results indicates an average SF 6 increase rate between March 1981 and June 1988 of 7.4 _+ 1.9% year -1 (1 sigma)which corresponds to a factor of 1.71 increase in the SF 6 VMR. If a linear increase in the SF 6 volume-mixing ratio with time is assumed, a slightly poorer fit to the measurements is obtained, but the difference is not significant given the estimated The present results can be compared with SF 6 trends measured at the surface [Rasmussen and Khalil, 1983] and in the stratosphere [Leifer et al, 1982;Leifer and Juzdan, 1985] and the atmospheric trend inferred from the depth profile of dissolved SF 6 in the northeast Atlantic ocean [Watson and Liddicoat, 1985]. Rasmussen and Khalil [1983] analyzed surface level electron-capture gas chromatography measurements of SF 6 obtained between 1979 and 1983 and derived annual exponential increase rates of 12.9 _+ 2.6% at the south pole and 8.6 -+ 2.3% in the pacific northwest and a global average annual rate of 10.5 -+ 2.4% (-+ values are the quoted 90% confidence limits).…”

Section: Data Analysis and Resultsmentioning

confidence: 73%

Long‐term trends in the concentrations of SF₆, CHClF₂, and COF₂ in the lower stratosphere from analysis of high‐resolution infrared solar occultation spectra

Rinsland¹,

Goldman²,

Murcray³

et al. 1990

Long-term trends in the concentrations of SF 6, CHCIF2 (CFC-22), and COF2 in the lower stratosphere have been derived from analysis of ca. 1980 and more recent infrared solar occultation spectra recorded near 32øN latitude at --•0.02-cm -1 resolution. Consistent sets of line parameters and spectral calibration methods have been used in the retrievals to minimize systematic error effects. Quoted error limits are 1 sigma estimated precisions. The SF 6 and CHCIF2 results are based on spectra recorded by balloon-borne interferometers in March 1981 and June 1988 and a comparison of these results with the Atmospheric Trace Molecule Spectroscopy (ATMOS) Experiment/Spacelab 3 measurements obtained in May 1985 near 30øN latitude. In the 13-18 km altitude range the mean measured SF 6 mixing ratio in parts per trillion by volume (pptv) increased from 1.17 +_ 0.21 in March 1981 to 2.02 +_ 0.20 pptv in June 1988, and the CHC1F 2 mixing ratio below 15 km altitude increased from 51 +_ 8 pptv in March 1981 to 102 +_ 10 pptv in June 1988. The CHC1F2 retrievals used new empirical CHCIF2 line parameters derived from 0.03-cm-1 resolution laboratory spectra recorded at six temperatures between 203 and 293 K' the derived mixing ratios are --•30% higher than obtained with earlier sets of line parameters, thereby removing a large discrepancy noted previously between IR and in situ measurements of CHCIF2. Assuming an exponential growth model for fitting the trends, SF 6 and CHC1F2 mean increase rates of 7.4% +_ 1.9% and 9.4% +_ 1.3% year -• are obtained, respectively which correspond to cumulative increases by factors of--• 1.7 and --•2.0 in the concentrations of these gases over the 7.2-year measurement period. Analysis of spectra recorded in October 1979 and April 1989 yields COF2 volume mixing ratios that are respectively 0.44 +_ 0.17 and 1.21 +_ 0.24 times the ATMOS/Spacelab 3 values, from which an average COF2 increase rate of 10.3 +_ 1.8% year -1 over this time period has been estimated. The present results are compared with previously reported observations and trends and with one-dimensional model calculations. The model calculated trends are in reasonably good agreement with the observations.