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Observations inside the November 1994 Antarctic stratospheric vortex and inside the April 1993 remnant Arctic stratospheric vortex by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer are reported. In both instances, elevated volume mixing ratios (VMRS) of carbon monoxide (CO) were measured. A peak Antarctic CO VMR of 60 ppbv (where 1 ppbv = 10(exp -9) per unit Volume) was measured at a potential temperature of 710 K (about 27 km), about 1 km below the altitude of a pocket of elevated NO(y) (total reactive nitrogen) at a deep minimum in N2O (<5 ppbv). The Arctic observations also show a region of elevated vortex CO with a peak VMR of 90 ppbv it 630-670 K (-25 km) but no corresponding enhancement in NO(sub y) perhaps because of stronger dynamical activity in the northern hemisphere polar winter and/or interannual variability in the production of mesospheric or lower thermospheric NO. By comparing vortex and extravortex observations of NO(y) obtained at the same N2O VMR, Arctic vortex denitrification of 5 +/- 2 ppbv at 470 K (at approximately 18 km) is inferred. We show that our conclusion of substantial Arctic winter 1992-1993 denitrification is robust by comparing our extravortex observations with previous polar measurements obtained over a wide range of winter conditions. Correlations of NO(y) with N2O measured at the same potential temperature by ATMOS in the Arctic vortex and at midlatitudes on board the ER-2 aircraft several weeks later lie along the same mixing line. The result demonstrates the consistency of the two data sets and confirms that the ER-2 sampled fragments of the denitrified Arctic vortex following its breakup. An analysis of the ATMOS Arctic measurements of total hydrogen shows no evidence for significant dehydration inside the vortex.

Vertical profiles of infrared cirrus extinction have been derived from tropical and subtropical upper tropospheric solar occultation spectra. The measurements were recorded by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the Atmospheric Laboratory for Applications and Sciences (ATLAS) 3 shuttle flight in November 1994. The presence of large numbers of small ice crystals is inferred from the appearance of broad extinction features in the 8-12 micron region. These features were observed near the tropopause and at lower altitudes. Vertical profiles of the ice extinction (/km) in microwindows at 831, 957, and 1204/cm have been retrieved from the spectra and analyzed with a model for randomly oriented spheroidal ice crystals. An area-equivalent spherical radius of 6 microns is estimated from the smallest ice crystals observed in the 8-12 gm region. Direct penetration of clouds into the lower stratosphere is inferred from observations of cloud extinction extending from the upper troposphere to 50 mbar (20 km altitude). Cloud extinction between 3 and 5 microns shows very little wavelength dependence, at least for the cases observed by the ATMOS instrument in the tropics and subtropics during ATLAS 3.

Vertical mixing ratio profiles of four relatively long-lives gases, HCN, C2H2, CO, and C2H6, have been retrieved from 0.01/cm resolution infrared solar occultation spectra recorded between latitudes of 5.3degN and 31.4degN. The observations were obtained by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the Atmospheric Laboratory for Applications and Science (ATLAS) 3 shuttle flight, 3-12 November 1994. Elevated mixing ratios below the tropopause were measured for these gases during several of the occultations. The positive correlations obtained between the simultaneously measured mixing ratios suggest that the enhancements are likely the result of surface emissions, most likely biomass burning and/or urban industrial activities, followed by common injection via deep convective transport of the gases to the upper troposphere. The elevated levels of HCN may account for at least part of the "missing NO," in the upper troposphere. Comparisons of the observations with values measured during a recent aircraft campaign are presented.

The ATMOS Fourier transform spectrometer was flown for a fourth time on the Space Shuttle as part of the ATLAS-3 instrument payload in November 1994. More than 190 sunrise and sunset occultation events provided measurements of more than 30 atmospheric trace gases at latitudes 3 - 49 deg N and 65 - 72 deg S, including observations both inside and outside the Antarctic polar vortex. The instrument configuration, data retrieval methodology, and mission background are described to place in context analyses of ATMOS data presented in this issue.

Volume mixing ratio (VMR) profiles of OCS, HCN, SF6, and CHClF2 (HCFC-22) have been measured near 30 deg N latitude by the Atmospheric Trace Molecule Spectroscopy Fourier transform spectrometer during shuttle flights on 29 April - 6 May 1985 and 3-2 November 1994. The change in the concentration of each molecule in the lower stratosphere has been derived for this 9 1/2-year period by comparing measurements between potential temperatures of 395 to 800 K (approximately 17 to 30 km altitude) relative to simultaneously measured values of the long-lived tracer N2O. Exponential rates of increase inferred for 1985-to 1994 from these comparisons are (0.1 plus or minus 0.4)% yr(exp-1) for OCS, (1.0 plus or minus 1.0)% yr(exp-1) for HCN, (8.0 +/- 0.7)% yr(exp-1) for SF6, and (8.0 +/- 1.0)% yr(exp-1) for CHClF2 (HCFC-22), 1 sigma. The lack of an appreciable trend for OCS suggests the background (i.e. nonvolcanic) source of stratospheric aerosol was the same during the two periods. These results are compared with trends reported in the literature.

Stratospheric volume mixing ratio profiles of carbon tetrafluoride, CF4, obtained with the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument during the ATLAS (Atmospheric Laboratory for Applications and Science) -3 mission of 1994 are reported. Overall the profiles are nearly constant over the altitude range 20 to 50 km, indicative of the very long lifetime of CF4 in the atmosphere. In comparison to the stratospheric values of CF4 inferred from the ATMOS/Spacelab 3 mission of 1985, the 1994 concentrations are consistent with an exponential increase of (1.6 +/- 0.6)% yr(exp -1). This increase is discussed with regard to previous results and likely sources of CF4 at the ground. Further, it is shown that simultaneous measurements of N2O and CF4 provide a means of constraining the lower limit of the atmospheric lifetime of CF4 at least 2,300 years, two sigma.

Partitioning between HCl and ClONO2 and among the main components of the reactive nitrogen family (NO, NO2, HNO3, ClONO2, N2O5, and HO2NO2) has been studied inside and outside the Antarctic stratospheric vortex based on ATMOS profiles measured at sunrise during the 3-12 November 1994 ATLAS-3 Shuttle mission. Elevated mixing ratios of HCl in the lower stratosphere with a peak of approximately 2.9 ppbv (10(exp -9) parts per volume) were measured inside the vortex near 500 K potential temperature (approximately 19 km). Maximum ClONO2 mixing ratios of approximately 1.2, approximately 1.4, and approximately 0.9 ppbv near 700 K (approximately 25 km) were measured inside, at the edge, and outside the vortex, respectively. Model calculations reproduce the higher levels of HCl and NO(x) (NO + NO2) inside the lower stratospheric vortex both driven by photochemical processes initiated by low O3. The high HCl at low O3 results from chemical production of HC1 via the reaction of enhanced Cl with CH4, limited production of ClONO2, and the descent of inorganic chlorine from higher altitudes.

Covers chlorine measurements in atmosphere, refer to abstract.

UNKNOWN

The ATMOS Fourier transform spectrometer was flown for a fourth time on the Space Shuttle as part of the ATLAS-3 instrument payload in November 1994. More than 190 sunrise and sunset occultation events provided measurements of more than 30 atmospheric trace gases at latitudes 3-49N and 65-72S, including observations both inside and outside the Antarctic polar vortex.

Mixing ratios of 3.44 ppbv (parts per billion by volume) and 1.23 ppbv for HCl and HF above 50 km, surrogates for total chlorine and fluorine, have been measured by the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment on a March 1992 flight of the Space Shuttle. Compared to the measured values obtained on a 1985 flight, these correspond to a 37% and 62% increase for HCl and HF, respectively. The derived trend in HCl (approx. 0.13 ppbv per year) is in good agreement with the model-predicted increase in chlorine loading of 0.13 ppbv per year, and with the measured trends in HCl total column abundance from reported ground-based observations. The main source of this change can be attributed to the release of man-made chlorofluorocarbons (CFC's) and hydro-chloro-fluoro-carbons (HCFC's). This new value for HCl represents an upper limit to the inorganic chlorine concentration in the stratosphere available for participation in photochemical processes which destroy ozone.

Stratospheric volume mixing ratio profiles of chlorine nitrate (ClONO2) have been retrieved from 0.01/cm resolution infrared solar occultation spectra recorded at latitudes between 14 deg N and 54 deg S by the atmospheric trace molecule spectroscopy Fourier transform spectrometer during the Atmospheric Laboratory for Applications and Science (ATLAS) 1 shuttle mission (March 24 to April 2, 1992). The results were obtained from nonlinear least squares fittings of the ClONO2 nu(sub 4) band Q branch at 780.21/cm with improved spectroscopic parameters generated on the basis of recent laboratory work. The individual profiles, which have an accuracy of about +/- 20%, are compared with previous observations and model calculations.

Volume mixing ratio profiles of COF2 have been derived through most of the stratosphere between 30 deg N and 54 deg S from series of 0.01-cm(exp -1) resolution infrared solar spectra recorded in the occultation mode by the atmospheric trace molecule spectroscopy (ATMOS) instrument during the ATLAS 1 space shuttle mission of March-April 1992. When compared with similar results obtained from the ATMOS/Spacelab 3 mission of April-May 1985, the cumulative increase in the burden of COF2 in the middle and upper stratosphere was found to be 67% for that 7-year time interval. By combining a subset of these COF2 results with upper stratospheric concentrations of HF also derived from the ATMOS observations, it was further found that the budget of inorganic fluorine above 35 km altitude increased by (60 +/- 10) % over the 1985-1992 time interval, which corresponds to an average exponential rate of increase of(6.7 +/- 1.1) % /yr , or a linear rate of increase referenced to 1985 of (8.5 +/- 1.3) % /yr at the 1(sigma) confidence level. The total inorganic F atom volume mixing ratio found in the upper stratosphere for 1985 and 1992 and the increase during this period mirror the rise in man-made fluorine-bearing compounds at the ground during the early to mid 1980s. This demonstrates the negligible impact of natural sources of fluorine, in particular volcanic activity, on the observed change of F in the upper stratosphere. Implications of the present findings and comparison with model results are discussed.

Infrared solar spectra recorded at the International Scientific Station of the Jungfraujoch (3580 m altitude), Switzerland, in 1950-1951 and from 1984 to 1992 have been analyzed to determine vertical column abundances of nitrous oxide (N2O) above the station. The best fit to the relatively dense set of measurements made between 1984 and 1992 indicates a mean exponential rate of increase equal to 0.36 +/- 0.06%/yr (1 sigma) and a seasonal modulation of 7.2% peak to peak, the minimum occurring at the end of the winter and the maximum in early September. The column abundances for April of the years 1951, 1984, and 1992 were found equal to 3.49 x 10(exp 18), 3.76 x 10(exp 18), and 3.87 x 10(exp 18) molecules/sq cm, respectively; they translate into N2O concentrations at the altitude of the Jungfraujoch equal to 275, 296, and 305 parts per billion by volume. These results indicate that the exponential rate of increase for 1951-1984 was equal to 0.23 +/- 0.04%/yr (1 sigma), thus substantially lower than for the 1984-1992 time interval and that the so-called preindustrial levels of N2O pertained until 1951 with most of the increase in atmospheric N2O occurring thereafter.