INCREASE IN LEVELS OF STRATOSPHERIC CHLORINE AND FLUORINE LOADING BETWEEN 1985 AND 1992

in Geophysical Research Letters (1994), 21(20), 2223-2226

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 ... [more ▼]

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 (similar to 0.13 ppbv per year) is in good agreement with the model-predicted increase in chlorine loading of 0.13 ppbv per year [Prather and Watson. 1990], 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 (CFCs) and hydrochlorofluorocarbons (HCFCs). 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. [less ▲]

Increase of carbonyl fluoride (COF2) in the stratosphere and its contribution to the 1992 budget of inorganic fluorine in the upper stratosphere

in Journal of Geophysical Research (1994), 99(D8), 16737-16743

Volume mixing ratio profiles of COF2 have been derived through most of the stratosphere between 30°N and 54°S from series of 0.01-cm−1 resolution infrared solar spectra recorded in the occultation mode by ... [more ▼]

Volume mixing ratio profiles of COF2 have been derived through most of the stratosphere between 30°N and 54°S from series of 0.01-cm−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−1, or a linear rate of increase referenced to 1985 of (8.5 ± 1.3) % yr−1 at the 1σ 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. [less ▲]

Monitoring of the atmospheric burdens of CH4, N2O, CO, CHCIF2 and CF2Cl2 above Central Europe during the last decade

in Environmental Monitoring & Assessment (1994, May), 31(1-2), 203-209

Based on high spectral resolution infrared solar observations made at the International Scientific Station of the Jungfraujoch, Switzerland, total vertical column abundances of 18 atmospheric gases have ... [more ▼]

Based on high spectral resolution infrared solar observations made at the International Scientific Station of the Jungfraujoch, Switzerland, total vertical column abundances of 18 atmospheric gases have been monitored routinely since 1984. The observed temporal evolutions in the columns of CH4, N2O, CO, CHClF2 (HCFC-22) and CF2Cl2 (CFC-12) are reported here as typical examples of this monitoring effort which is conducted within the frame of ''Global Change'' and ''Network for the Detection of Stratospheric Change'' programs. [less ▲]

SECULAR EVOLUTION OF THE VERTICAL COLUMN ABUNDANCES OF CHCLF2 (HCFC-22) IN THE EARTH'S ATMOSPHERE INFERRED FROM GROUND-BASED IR SOLAR OBSERVATIONS AT THE JUNGFRAUJOCH AND AT KITT-PEAK, AND COMPARISON WITH MODEL-CALCULATIONS

in Journal of Atmospheric Chemistry (1994), 18(2), 129-148

Series of high-resolution infrared solar spectra recorded at the International Scientific Station of the Jungfraujoch, Switzerland, between 06/1986 and 11/1992, and at Kitt Peak National Observatory ... [more ▼]

Series of high-resolution infrared solar spectra recorded at the International Scientific Station of the Jungfraujoch, Switzerland, between 06/1986 and 11/1992, and at Kitt Peak National Observatory, Tucson, Arizona (U.S.A.), from 12/1980 to 04/1992, have been analyzed to provide a comprehensive ensemble of vertical column abundances of CHClF2 (HCFC-22; Freon-22) above the European and the North American continents. The columns were derived from nonlinear least-squares curve fittings between synthetic spectra and the observations containing the unresolved 2nu6 Q-branch absorption of CHClF2 at 829.05 cm-1. The changes versus time observed in these columns were modeled assuming both an exponential and a linear increase with time. The exponential rates of increase at one-sigma uncertainties were found equal to (7.0 +/- 0.35)%/yr for the Junfraujoch data and (7.0 +/- 0.23)%/yr for the Kitt Peak data. The exponential trend of 7.0%/yr found at both stations widely separated in location can be considered as representative of the global increase of the CHClF2 burden in the Earth's atmosphere during the period 1980 to 1992. When assuming two realistic vertical volume mixing ratio profiles for CHClF2 in the troposphere, one quasi constant and the other decreasing by about 13% from the ground to the tropopause, the concentrations for mid-1990 were found to lie between 97 and 111 pptv (parts per trillion by volume) at the 3.58 km altitude of the Jungfraujoch and between .97 and 103 pptv at Kitt Peak, 2.09 km above sea level. Corresponding values derived from calculations using a high vertical resolution-2D model and recently compiled HCFC-22 releases to the atmosphere, were equal to 107 and 105 pptv, respectively, in excellent agreement with the measurements. The model calculated lifetime of CHClF2 was found equal to 15.6 years. The present results are compared critically with similar data found in the literature. On average, the concentrations found here are lower by 15-20% than those derived from in situ investigations; this difference cannot be explained by the absolute uncertainty of +/- 11% assigned presently to the infrared remote measurements. [less ▲]

Spectroscopic Measurements of Atmospheric Changes (SMAC), Belgian Impulse Programme GLOBAL CHANGE

in Proceedings of the Symposium of Belgian Impulse Programme "Global Change" (1993)

GROUND-BASED INFRARED MEASUREMENTS OF CARBONYL SULFIDE TOTAL COLUMN ABUNDANCES - LONG-TERM TRENDS AND VARIABILITY

in Journal of Geophysical Research (1992), 97(D5), 5995-6002

Total vertical column abundances of carbonyl sulfide (OCS) have been derived from time series of high-resolution infrared solar absorption spectra recorded at the National Solar Observatory McMath solar ... [more ▼]

Total vertical column abundances of carbonyl sulfide (OCS) have been derived from time series of high-resolution infrared solar absorption spectra recorded at the National Solar Observatory McMath solar telescope facility on Kitt Peak (altitude 2.09 km, latitude 31.9-degrees-N, longitude 111.6-degrees-W), southwest of Tucson, Arizona, and at the International Scientific Station of the Jungfraujoch (altitude 3.58 km, latitude 46.5-degrees-N, longitude 8.0-degrees-E), in the Swiss Alps. The analysis of both data sets is based on nonlinear least squares spectral fittings of narrow intervals centered on lines of the intense nu-3 band of OCS, the P(37) transition at 2045.5788 cm-1 and the P(15) transition at 2055.8609 cm-1, with a consistent set of spectroscopic line parameters. The Kitt Peak measurements, recorded on 30 different days between May 1977 and March 1991, show a 10% peak-to-peak seasonal cycle with a summer maximum and a winter minimum and a trend in the total column abundance equal to (0.1 +/- 0.2)% yr-1, 2-sigma. Jungfraujoch solar spectra recorded on 67 different days between October 1984 and April 1991 have been analyzed. The fitted trend in the Jungfraujoch total columns, (-0.1 +/- 0.5)% yr-1, 2-sigma, is consistent with the Kitt Peak trend results within the errors. The Jungfraujoch total columns show a more complex seasonal variation than noted in the Kitt Peak data. The mean of the daily averaged total columns, 8.44 x 10(15) molecules cm-2 above Kitt Peak and 6.41 x 10(15) molecules cm-2 above the Jungfraujoch station, correspond respectively to mean tropospheric mixing ratios of 0.54 +/- 0.04 and 0.52 +/- 0.04 parts per billion by volume; these values are consistent with previously reported remote and in situ measurements. Taken together, the results from the two sites indicate that there has been no significant change in the OCS total column abundance at northern mid-latitudes over the last decade. [less ▲]

The 1985 chlorine and fluorine inventories in the stratosphere based on atmos observations at 30-degrees north latitude

in Journal of Atmospheric Chemistry (1992), 15(2), 171-186

The set of high-resolution infrared solar observations made with the Atmospheric Trace Molecule Spectroscopy (ATMOS) - Fourier transform spectrometer from onboard Spacelab 3 (30 April-1 May 1985) has been ... [more ▼]

The set of high-resolution infrared solar observations made with the Atmospheric Trace Molecule Spectroscopy (ATMOS) - Fourier transform spectrometer from onboard Spacelab 3 (30 April-1 May 1985) has been used to evaluate the total budgets of the odd chlorine and fluorine chemical families in the stratosphere. These budgets are based on volume mixing ratio profiles measured for HCl, HF, CH3Cl, ClONO2, CCl4, CCl2F2, CCl3F, CHClF2, CF4, COF2, and SF6, near 30-degrees north latitude. When including realistic concentrations for species not measured by ATMOS, i.e., the source gases CH3CCl3, and C2F3Cl3 below 25 km, and the reservoirs ClO, HOCl and COFCl between 15 and 40 km (five gases actually measured by other techniques), the 30-degrees-N zonal 1985 mean total mixing ratio of chlorine, Cl, was found to be equal to (2.58 +/- 0.10) ppbv (parts per billion by volume) throughout the stratosphere, with no significant decrease near the stratopause. The results for total fluorine indicate a slight, but steady, decrease of its volume mixing ratio with increasing altitude, around a mean stratospheric value of (1.15 +/- 0.12) ppbv. Both uncertainties correspond to one standard deviation. These mean springtime 1985 stratospheric budgets are commensurate with values reported for the tropospheric Cl and F concentrations in the early 1980s, when allowance is made for the growth rates of their source gases at the ground and the time required for tropospheric air to be transported into the stratosphere. The results are discussed with emphasis on conservation of fluorine and chlorine and the partitioning among source, sink, and reservoir gases throughout the stratosphere. [less ▲]

Rotational analysis of the a3Πr-X1Σ+ transition of 69Ga35Cl

in Journal of Molecular Spectroscopy (1991), 150(2), 477-485

Six bands (0-0, 0-1, 0-2, 1-0, 2-0, 2-1) of 69Ga35Cl have been fully analyzed for the a-X transition, yielding equilibrium constants for the a3Π, state.

Rotational analysis of the a3Πr-X1Σ+ transition of AlI

in Journal of Molecular Spectroscopy (1990), 143(2), 359-365

The a3Πr-X1Σ+ transition of Al I has been analyzed for the first time. Accurate rotational and vibrational constants are given for the a3Πr electronic state.

The a3Πr-X1Σ+ transition of BI

in Journal of Molecular Spectroscopy (1990), 141(1), 145-148

A new study of the a3Πr-X1Σ+ transition of BI has yielded precise molecular constants including spin-orbit and Λ-doubling constants of the a3Πr electronic state.