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See detailRecent trends of inorganic chlorine and halogenated source gases above the Jungfraujoch and Kitt Peak stations derived from high-resolution FTIR solar observations
Mahieu, Emmanuel ULg; Rinsland, Curtis P.; Gardiner, Tom et al

in Geophysical Research Abstracts (2010), 12(EGU2010-2420-3),

The longest series of Fourier Transform Infrared (FTIR) high spectral resolution solar absorption observations are available from the Jungfraujoch and Kitt Peak stations, located at 46.5ºN and 30.9ºN ... [more ▼]

The longest series of Fourier Transform Infrared (FTIR) high spectral resolution solar absorption observations are available from the Jungfraujoch and Kitt Peak stations, located at 46.5ºN and 30.9ºN, respectively. State-of-the-art interferometers are operated at these sites within the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, visit http://www.ndacc.org). These instruments allow to record spectra on a regular basis, under clear-sky conditions, using a suite of optical filters which altogether cover the 2 to 16 micron spectral range. Numerous absorption features characterized in the HITRAN compilations (e.g. Rothman et al., 2008) are encompassed in this mid-infrared region. Their analyses with either the SFIT-1 or SFIT-2 algorithm allow retrieving total columns of the target gases. Moreover, information on their distribution with altitude can generally be derived when using SFIT-2 which implements the Optimal Estimation Method of Rodgers (1990). Among the two dozen gases of atmospheric interest accessible to the ground-based FTIR technique, we have selected here a suite of long-lived halogenated species: HCl, ClONO2, CCl2F2, CCl3F, CHClF2, CCl4 and SF6. Time series available from the two sites will be presented, compared and critically discussed. In particular, changes in the abundances of theses gases since the peak in inorganic chlorine (Cly, which occurred in 1996-1997) and their intra-annual variability will be characterized with a statistical tool using bootstrap resampling (Gardiner et al., 2008). Trends and their associated uncertainties will be reported and put into perspective with the phase-out regulations of the production of ozone depleting substances adopted and implemented by the Montreal Protocol, its Amendments and Adjustments. For instance, the trends affecting the reservoir species HCl, ClONO2, and their summation which is a good proxy of the total inorganic chlorine, have been calculated using all available daily mean measurements from January 1996 onwards. The following values were obtained for Jungfraujoch, when using 1996 as the reference year: -0.90±0.10%/yr for HCl, -0.92±0.26 %/yr for ClONO2, and -0.96±0.14 %/yr for Cly; in all cases, the uncertainties define the 95% confidence interval around the trend values. For Kitt Peak, the corresponding trends are: -0.55±0.34 %/yr for HCl, -1.27±0.84 %/yr for ClONO2 and -0.61±0.51 %/yr for Cly, they are statistically consistent with the Jungfraujoch rates of decrease. Further trend data will be presented at the EGU General Assembly while supplementary information on Jungfraujoch results will be available from communications at the same meeting by Duchatelet et al. (2010), Lejeune et al (2010) and Rinsland et al (2010). Comparisons with model data are also foreseen. [less ▲]

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See detailTrend of lower stratospheric methane (CH4) from Atmospheric Chemistry Experiment (ACE) and Atmospheric Trace Molecule Spectroscopy (ATMOS) measurements
Rinsland, Curtis P.; Chiou, Linda S.; Boone, C. D. et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (2009), 110(13), 1066-1071

The long-term trend of methane (CH4) in the lower stratosphere has been estimated for the 1985 to 2008 time period by combining spaceborne solar occultation measurements recorded with high spectral ... [more ▼]

The long-term trend of methane (CH4) in the lower stratosphere has been estimated for the 1985 to 2008 time period by combining spaceborne solar occultation measurements recorded with high spectral resolution Fourier transform spectrometers (FTSs). Volume mixing ratio (VMR) FTS measurements from the ATMOS (Atmospheric Trace Molecule Spectroscopy) FTS covering 120-10 hPa (~16 to 30 km altitude) at 25°N-35°N latitude from 1985 and 1994 have been combined with Atmospheric Chemistry Experiment (ACE) SCISAT-1 FTS measurements covering the same latitude and pressure range from 2004 to 2008. The CH4 trend was estimated by referencing the VMRs to those measured for the long-lived constituent N2O to account for the dynamic history of the sampled airmasses. The combined measurement set shows that the VMR increase measured by ATMOS has been replaced by a leveling off during the ACE measurement time period. Our conclusion is consistent with both remote sensing and in situ measurements of the CH4 trend obtained over the same time span. [less ▲]

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See detailMeasurements of long-term changes in atmospheric OCS (carbonyl sulfide) from infrared solar observations
Rinsland, Curtis P.; Chiou, Linda S.; Mahieu, Emmanuel ULg et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (2008), 109(16), 2679-2686

Multi-decade atmospheric OCS (carbonyl sulfide) infrared measurements have been analyzed with the goal of quantifying long-term changes and evaluating the consistency of the infrared atmospheric OCS ... [more ▼]

Multi-decade atmospheric OCS (carbonyl sulfide) infrared measurements have been analyzed with the goal of quantifying long-term changes and evaluating the consistency of the infrared atmospheric OCS remote-sensing measurement record. Solar-viewing grating spectrometer measurements recorded in April 1951 at the Jungfraujoch station (46.5°N latitude, 8.0°E longitude, 3.58 km altitude) show evidence for absorption by lines of the strong ν3 band of OCS at 2062 cm(−1). The observation predates the earliest previously reported OCS atmosphere remote-sensing measurement by two decades. More recent infrared ground-based measurements of OCS have been obtained primarily with high-resolution solar-viewing Fourier transform spectrometers (FTSs). Long-term trends derived from this record span more than two decades and show OCS columns that have remained constant or have decreased slightly with time since the Mt. Pinatubo eruption, though retrievals assuming different versions of public spectroscopic databases have been impacted by OCS ν3 band line intensity differences of 10%. The lower stratospheric OCS trend has been inferred assuming spectroscopic parameters from the high-resolution transmission (HITRAN) 2004 database. Volume mixing ratio (VMR) profiles measured near 30°N latitude with high-resolution solar-viewing FTSs operating in the solar occultation mode over a 22 years time span were combined. Atmospheric Trace MOlecucle Spectroscopy (ATMOS) version 3 FTS measurements in 1985 and 1994 were used with Atmospheric Chemistry Experiment (ACE) measurements during 2004–2007. Trends were calculated by referencing the measured OCS VMRs to those of the long-lived constituent N2O to account for variations in the dynamic history of the sampled airmasses. Means and 1-sigma standard deviations of VMRs (in ppbv, or 10−9 per unit air volume) averaged over 30–100 hPa from measurements at 25–35°N latitude are 0.334±0.089 ppbv from 1985 (ATMOS Spacelab 3 measurements), 0.297±0.094 ppbv from 1994 ATLAS 3 measurements, 0.326±0.074 ppbv from ACE 2004 measurements, 0.305±0.096 ppbv from ACE 2005 measurements, 0.328±0.074 from ACE 2006 measurements, and 0.305±0.090 ppbv from ACE measurements through August 2007. Assuming these parameters, we conclude that there has been no statistically significant trend in lower stratospheric OCS over the measurement time span. We discuss past measurement sets, quantify the impact of changes in infrared spectroscopic parameters on atmospheric retrievals and trend measurements, and discuss OCS spectroscopic uncertainties of the current ν3 band parameters in public atmospheric databases. [less ▲]

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See detailLong-term trends of tropospheric carbon monoxide and hydrogen cyanide from analysis of high resolution infrared solar spectra
Rinsland, Curtis P.; Goldman, Aaron; Hannigan, James W. et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (2007), 104(1), 40-51

Long-term trend and seasonal variation of the mean free tropospheric volume mixing ratios of carbon monoxide (CO) and hydrogen cyanide (HCN) have been derived from analysis of a time series of solar ... [more ▼]

Long-term trend and seasonal variation of the mean free tropospheric volume mixing ratios of carbon monoxide (CO) and hydrogen cyanide (HCN) have been derived from analysis of a time series of solar absorption spectra recorded from the US National Solar Observatory on Kitt Peak (31.9 degrees N, 111.6 degrees W, 2.09 km altitude) spanning almost three decades. The results of a fit to the CO 258 daily averages from May 1977 to April 2005 as a function of time with a model that assumes a sinusoidal seasonal cycle and a linear long-term trend with time yield a mean volume mixing ratio of 102 +/- 3) parts per billion (10(-9) per unit volume) below 10km altitude, I sigma. The CO measurements show a seasonal cycle with a maximum in March and a minimum in September with an amplitude of (22.3 +/- 1.5)% relative to the mean. The best-fit corresponds to a long-term CO trend of (0.15 +/- 0.14)% yr(-1), 1 sigma, relative to the mean. To quantify the possible impact of periods of intense fires, the CO measurements have been compared with the measurements of HCN, a well-documented emission product of biomass burning with a lifetime of similar to 5 months. The best fit to the full HCN time series of 208 daily averages from May 1978 to April 2005 results in a mean volume mixing ratio of (0.219 +/- 0.007) ppbv below 10 km altitude with a similar seasonal cycle, though with a lower relative amplitude than for CO. Although same-day enhancements up to a factor of 1.87 for HCN and 1.24 for CO were measured relative to values predicted by a fit to the time series that accounts for the seasonal cycles and trends of both molecules, excluding time periods of elevated fire emissions has no significant impact on the best-fit long-term free tropospheric CO and HCN trends. Our result of no long-term CO trend since the late 1970s suggests that the global average long-term decline reported from 1990 through 1995 measurements has not continued in the free troposphere. Similarly, a fit to the full time series of 208 HCN free tropospheric daily averages with the same model yields an average 2.09-10km mixing ratio of 0.219ppbv and a long-term trend of (-0.12 +/- 0.14) % yr(-1), 1 sigma, relative to the mean since 1978, also indicating no significant long-term trend above the lower mid-latitude continental US Kitt Peak station. The results for both molecules suggest the site was not significantly impacted by summer boreal fires during the time span of the measurements that in some years cause widespread pollution above northern higher latitude sites. (c) 2006 Elsevier Ltd. All rights reserved. [less ▲]

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See detailLong-term trend of CH4 at northern mid-latitudes: Comparison between ground-based infrared solar and surface sampling measurements
Rinsland, Curtis P.; Goldman, Aaron; Elkins, James W. et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (2006), 97(3), 457-466

We report average tropospheric CH4 volume mixing ratios retrieved from a 27 year time series of high spectral resolution infrared solar absorption measurements recorded between May 1977 and July 2004 at ... [more ▼]

We report average tropospheric CH4 volume mixing ratios retrieved from a 27 year time series of high spectral resolution infrared solar absorption measurements recorded between May 1977 and July 2004 at the US National Solar Observatory station on Kitt Peak (31.9 degrees N, 111.6 degrees W, 2.09 km altitude) and their comparison with surface in situ sampling measurements recorded between 1983 and 2004 at the Climate Monitoring and Diagnostics Laboratory (CMDL) station at Niwot Ridge, Colorado (40.0 degrees N, 105.5 degrees W, 3013 m altitude). The two measurement sets therefore overlap for the 1983-2004 time period. An average tropospheric volume mixing ratios of 1814 +/- 48 ppbv (1 ppbv = 10(-9) per unit volume) has been derived from the solar absorption time series with a best-fit increase rate trend equal to 8.26 +/- 2.20 ppbv yr(-1) in 1983 decreasing to 1.94 +/- 3.69 ppbv yr(-1) in 2003. The CMDL measurements also show a continuous long-term CH4 volume mixing ratio rise, with subsequent slowing down. A mean ratio of the retrieved average tropospheric volume mixing ratio to the CMDL volume mixing ratio for the overlapping time period of 1.038 +/- 0.034 indicates agreement between both data sets within the quantified experimental errors. (C) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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See detailLong-term stratospheric carbon tetrafluoride (CF4) increase inferred from 1985-2004 infrared space-based solar occultation measurements
Rinsland, Curtis P.; Mahieu, Emmanuel ULg; Zander, Rodolphe ULg et al

in Geophysical Research Letters (2006), 33(2),

The long-term stratospheric carbon tetrafluoride (CF4) increase has been determined from infrared high spectral resolution solar occultation Fourier transform spectrometer measurements between 3 and 50 ... [more ▼]

The long-term stratospheric carbon tetrafluoride (CF4) increase has been determined from infrared high spectral resolution solar occultation Fourier transform spectrometer measurements between 3 and 50 hPa (similar to 20 to 40 km altitude) and latitudes from 50 degrees N to 50 degrees S during 1985, 1992, 1993, 1994, and 2004. The 1985 to 1994 measurements were recorded from the ATMOS ( Atmospheric Trace MOlecule Spectroscopy) instrument at 0.01 cm(-1) resolution and in 2004 by the Atmospheric Chemistry Experiment ( ACE) instrument at 0.02 cm(-1) resolution. Stratospheric volume mixing ratios, inferred from a polynomial fit to averages from the time periods considered here, increased from 49.37 +/- 2.60 pptv (10(-12) per unit volume) in 1985 to 58.38 +/- 4.14 pptv in 1992, 60.46 +/- 2.97 pptv in 1993, 60.11 +/- 3.60 pptv in 1994 and to 70.45 +/- 3.40 pptv in 2004. The stratospheric CF4 mixing ratio has continued to increase but at a slower rate than in previous years, for example, (1.14 +/- 0.68)% yr(-1) in 2004 as compared to (2.77 +/- 0.47)% yr(-1) in 1985, 1 sigma. Correlations of CF4 with N2O taking into account the increase of N2O with time also show the increase in the stratospheric CF4 burden over the two decade measurement time span. Our space-based measurements show that the slowdown in the rate of CF4 accumulation previously reported from surface measurements through 1997 has propagated to the stratosphere and is continuing. Citation: Rinsland, C. P., E. Mahieu, R. Zander, R. Nassar, P. Bernath, C. Boone, and L. S. Chiou (2006), Long-term stratospheric carbon tetrafluoride (CF4) increase inferred from 1985-2004 infrared space-based solar occultation measurements, Geophys. Res. Lett., 33, L02808, doi:10.1029/2005GL024709. [less ▲]

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See detailTrends of HF, HCl, CCl2F2, CCl3F, CHClF2 (HCFC-22), and SF6 in the lower stratosphere from Atmospheric Chemistry Experiment (ACE) and Atmospheric Trace Molecule Spectroscopy (ATMOS) measurements near 30 degrees N latitude
Rinsland, Curtis P.; Boone, Christopher D.; Nassar, Ray et al

in Geophysical Research Letters (2005), 32(16),

[ 1] Volume mixing ratios ( VMRs) of HF, HCl, CCl2F2, CHClF2 ( HCFC-22), and SF6 in the lower stratosphere have been derived from solar occultation measurements recorded with spaceborne high resolution ... [more ▼]

[ 1] Volume mixing ratios ( VMRs) of HF, HCl, CCl2F2, CHClF2 ( HCFC-22), and SF6 in the lower stratosphere have been derived from solar occultation measurements recorded with spaceborne high resolution Fourier transform spectrometers. Atmospheric Chemistry Experiment ( ACE) VMRs measured during 2004 have been compared with those obtained in 1985 and 1994 by the Atmospheric Trace MOlecule Spectroscopy ( ATMOS) instrument. Trends are estimated by referencing the measured VMRs to those of the long-lived constituent N2O to account for variations in the dynamic history of the sampled air masses. Pressure-gridded measurements covering 10-100 hPa ( similar to 16 to 30 km altitude) were used in the analysis that includes typically 25 degrees N-35 degrees N latitude. The VMR changes provide further evidence of the impact of the emission restrictions imposed by the Montreal Protocol and its strengthening amendments and adjustments and are consistent with model predictions and known sources and sinks of halocarbons. Decreases in the lower stratospheric mixing ratios of CCl3F and HCl are measured in 2004 with respect to 1994, providing important confirmation of recent ground-based solar absorption measurements of a decline in inorganic chlorine. Trends estimates are compared with other reported measurements and model predictions. [less ▲]

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See detailLong-term evolution in the tropospheric concentration of chlorofluorocarbon 12 (CCl2F2) derived from high-spectral resolution infrared solar absorption spectra: retrieval and comparison with in situ surface measurements
Rinsland, Curtis P.; Goldman, Aaron; Mahieu, Emmanuel ULg et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (2005), 92(2), 201-209

The average tropospheric volume mixing ratios of chlorofluorocarbon 12 (CCl2F2) have been retrieved from high-spectral resolution ground-based infrared solar-absorption spectra recorded from March 1982 to ... [more ▼]

The average tropospheric volume mixing ratios of chlorofluorocarbon 12 (CCl2F2) have been retrieved from high-spectral resolution ground-based infrared solar-absorption spectra recorded from March 1982 to October 2003 with the McMath Fourier transform spectrometer at the US National Solar Observatory facility on Kitt Peak in southern Arizona (31.9degreesN, 111.6degreesW, 2.09 km altitude). The retrievals are based on fits to the unresolved v(8) band Q-branches near 922 cm(-1) using the SFIT2 retrieval algorithm. The annual increase rate was equal to (16.88 +/- 1.37) parts per trillion (10(-12)) by volume at the beginning of the time series, March 1982, or (4.77 +/- 0.04)%, 1 sigma, declining progressively to (2.49 +/- 1.24) parts per trillion, by volume at the end, October 2003, or (0.46 +/- 0.24)%, 1 sigma. Average tropospheric mixing ratios from the solar spectra have been compared with average surface flask and in situ sampling measurements from the Climate Monitoring and Diagnostics Laboratory (CMDL) station at Niwot Ridge, CO, (USA) (40.0degreesN, 105.5degreesW, 3013 m altitude). The average ratio and standard deviation of the monthly means of the retrieved tropospheric mixing ratios relative to the CMDL surface mixing ratios is (1.01 +/- 0.03) for the overlapping time period. Both datasets demonstrate the progressive impact of the Montreal protocol and its strengthening amendments on the trend of CCl2F2, though a tropospheric decrease has yet to be observed. (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

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See detailPost-Mount Pinatubo eruption ground-based infrared stratospheric column measurements of HNO3, NO, and NO2 and their comparison with model calculations
Rinsland, Curtis P.; Weisenstein, Debra K.; Ko, Malcolm K. W. et al

in Journal of Geophysical Research. Atmospheres (2003), 108(D15),

[1] Infrared solar spectra recorded between July 1991 to March 1992 and November 2002 with the Fourier transform spectrometer on Kitt Peak (31.9 degrees N latitude, 111.6 degrees W longitude, 2.09 km ... [more ▼]

[1] Infrared solar spectra recorded between July 1991 to March 1992 and November 2002 with the Fourier transform spectrometer on Kitt Peak (31.9 degrees N latitude, 111.6 degrees W longitude, 2.09 km altitude) have been analyzed to retrieve stratospheric columns of HNO3, NO, and NO2. The measurements cover a decade time span following the June 1991 Mount Pinatubo volcanic eruption and were recorded typically at 0.01 cm(-1) spectral resolution. The measured HNO3 stratospheric column shows a 20% decline from 9.16 x 10(15) molecules cm(-2) from the first observation in March 1992 to 7.40 x 10(15) molecules cm(-2) at the start of 1996 reaching a broad minimum of 6.95 x 10(15) molecules cm(-2) thereafter. Normalized daytime NO and NO2 stratospheric column trends for the full post-Pinatubo eruption time period equal (+ 1.56 +/- 0.45)% yr(-1), 1 sigma, and (+ 0.52 +/- 0.32)% yr(-1), 1 sigma, respectively. The long-term trends are superimposed on seasonal cycles with ~10% relative amplitudes with respect to mean values, winter maxima for HNO3 and summer maxima for NO and NO2. The measurements have been compared with two-dimensional model calculations utilizing version 6.1 Stratospheric Aerosol and Gas Experiment ( SAGE) II sulfate aerosol surface area density measurements through 1999 and extended to the end of the time series by repeating the 1999 values. The model-calculated HNO3, NO, and NO2 stratospheric column time series agree with the measurements to within ~8% after taking into account the vertical sensitivity of the ground-based measurements. The consistency between the measured and model-calculated stratospheric time series confirms the decreased impact on stratospheric reactive nitrogen chemistry of the key heterogeneous reaction that converts reactive nitrogen to its less active reservoir form as the lower-stratospheric aerosol surface area density declined by a factor of ~20 after the eruption maximum. [less ▲]

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See detailLong-term trends of inorganic chlorine from ground-based infrared solar spectra: Past increases and evidence for stabilization
Rinsland, Curtis P.; Mahieu, Emmanuel ULg; Zander, Rodolphe ULg et al

in Journal of Geophysical Research (2003), 108(D8), 4252

Long-term time series of hydrogen chloride (HCl) and chlorine nitrate (ClONO2) total column abundances has been retrieved from high spectral resolution ground-based solar absorption spectra recorded with ... [more ▼]

Long-term time series of hydrogen chloride (HCl) and chlorine nitrate (ClONO2) total column abundances has been retrieved from high spectral resolution ground-based solar absorption spectra recorded with infrared Fourier transform spectrometers at nine NDSC (Network for the Detection of Stratospheric Change) sites in both Northern and Southern Hemispheres. The data sets span up to 24 years and most extend until the end of 2001. The time series of Cly (defined here as the sum of the HCl and ClONO2 columns) from the three locations with the longest time-span records show rapid increases until the early 1990s superimposed on marked day-to-day, seasonal and inter-annual variability. Subsequently, the buildup in Cly slows and reaches a broad plateau after 1996, also characterized by variability. A similar time evolution is also found in the total chlorine concentration at 55 km altitude derived from Halogen Occultation Experiment (HALOE) global observations since 1991. The stabilization of inorganic chlorine observed in both the total columns and at 55 km altitude indicates that the near-global 1993 organic chlorine (CCly) peak at the Earth’s surface has now propagated over a broad altitude range in the upper atmosphere, though the time lag is difficult to quantify precisely from the current data sets, due to variability. We compare the three longest measured time series with two-dimensional model calculations extending from 1977 to 2010, based on a halocarbon scenario that assumes past measured trends and a realistic extrapolation into the future. The model predicts broad Cly maxima consistent with the long-term observations, followed by a slow Cly decline reaching 12–14% relative to the peak by 2010. The data reported here confirm the effectiveness of the Montreal Protocol and its Amendments and Adjustments in progressively phasing out the major man-related perturbations of the stratospheric ozone layer, in particular, the anthropogenic chlorine-bearing source gases. [less ▲]

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See detailSF6 ground-based infrared solar absorption measurements: long-term trend, pollution events, and a search for SF5CF3 absorption
Rinsland, Curtis P.; Goldman, Aaron; Stephen, T. M. et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (2003), 78(1), 41-53

Infrared solar spectra recorded with the Fourier transform spectrometer in the McMath solar telescope complex on Kitt Peak (31.9degreesN latitude, 111.6degreesW, 2.09 km altitude), southwest of Tucson ... [more ▼]

Infrared solar spectra recorded with the Fourier transform spectrometer in the McMath solar telescope complex on Kitt Peak (31.9degreesN latitude, 111.6degreesW, 2.09 km altitude), southwest of Tucson, Arizona, have been analyzed to retrieve average SF6 tropospheric mixing ratios over a two-decade time span. The analysis is based primarily on spectral fits to absorption by the intense, unresolved nu(3) band Q branch at 947.9 cm(-1). A best fit to measurements recorded with SF6 near typical background concentrations yields a SF6 increase in the average tropospheric mixing ratio from 1.13 pptv (10(-12) per unit volume) in March 1982 to 3.77 pptv in March 2002. The long-term increase by a factor of 3.34 over the time span is consistent with the rapid growth of surface mixing ratios measured in situ at Northern Hemisphere remote stations, though the infrared measurements show a large scatter. Average tropospheric mixing ratio enhancements above background by 2-3 orders of magnitude have been identified in spectra recorded on 5 days between November 1988 and April 1997. These spectra were individually analyzed in an attempt to detect the strongest 8-12 mum band of SF5CF3, a molecule recently identified with an atmospheric growth that has closely paralleled the rise in SF6 during the past three decades. Absorption by the strongest SF5CF3 band was predicted to be above the noise level in the Kitt Peak spectrum with the highest average mean tropospheric SF6 mixing ratio, assuming the reported atmospheric SF5CF3/SF6 ratio and a room temperature absorption cross sections reported for the SF5CF3 903-cm(-1) band. An upper limit of 8 x 10(15) molecules cm(-2) for the SF5CF3 total column was estimated for this case. We hypothesize that the highly elevated SF6 levels above Kitt Peak resulted from a local release experiment rather than production via electrochemical fluoridation of intermediate products, the proposed source of atmospheric SF5CF3. The absence of the SF5CF3 feature in the spectra with elevated SF6 is consistent with the absence of SF5CF3 reported in a pure SF6 sample. Published by Elsevier Science Ltd. [less ▲]

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See detailStratospheric HF column abundances above Kitt Peak (31.9 degrees N latitude): trends from 1977 to 2001 and correlations with stratospheric HCl columns
Rinsland, Curtis P.; Zander, Rodolphe ULg; Mahieu, Emmanuel ULg et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (2002), 74(2), 205-216

Time series of stratospheric hydrogen fluoride (HF) column abundances have been derived from infrared solar absorption spectra recorded for 195 days between May 1977 and June 2001 at a spectral resolution ... [more ▼]

Time series of stratospheric hydrogen fluoride (HF) column abundances have been derived from infrared solar absorption spectra recorded for 195 days between May 1977 and June 2001 at a spectral resolution of typically 0.01 cm(-1). The measurements were made at the US National Solar Observatory facility on Kitt Peak, Arizona, USA (31.9degreesN, 111.6degreesW, 2.09 km altitude) and have been analyzed with the SFIT2 algorithm, which is based on a semi-empirical application of the optimal estimation method. The measurements show a continuous buildup of the stratospheric HF column over the 24-yr period superimposed on short-term variations and a seasonal cycle with spring maxima and autumn minima. The measured stratospheric HF columns increased by a factor of 4.7, from 2.03 x 10(14) molecule cm(-2) in May 1977 to 9.49 x 10(14) molecule cm(-2) in June 2001. A best fit with a model that assumes an exponential increase in the stratospheric HF column with time superimposed on a sinusoidal seasonal cycle yields an average rate of stratospheric HF column increase of (4.30 +/- 0.15% yr(-1)), 1 sigma. The rate of increase is nearly a factor of two less than that derived previously from 1977 to 1990 Kitt Peak total columns, which indicates a significant slowdown in the increase rate during the 1990s, consistent with the trends from recent near-global lower mesospheric satellite remote and surface in situ measurements. Day-to-day stratospheric HIT columns are highly correlated with the same day stratospheric HCl columns as a result of common transport of lower and higher latitude air to above the station. Extrapolation of the linear relation between the two sets of stratospheric columns indicates a background HCl column of 1 x 10(15) molecule cm(-2) for zero HF, consistent with a previous estimate from 1977 to 1990 HF and HCl Kitt Peak total column measurements and a 1973 HCl measurement above the station. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailMultiyear infrared solar spectroscopic measurements of HCN, CO, C2H6,and C2H2 tropospheric columns above Lauder, New Zealand (45 degrees S latitude)
Rinsland, Curtis P.; Jones, Nicholas B.; Connor, Brian J. et al

in Journal of Geophysical Research. Atmospheres (2002), 107(D14),

[1] Near-simultaneous, 0.0035 or 0.007 cm(-1) resolution infrared solar absorption spectra of tropospheric HCN, C2H2, CO, and C2H6 have been recorded from the Network for the Detection of Stratospheric ... [more ▼]

[1] Near-simultaneous, 0.0035 or 0.007 cm(-1) resolution infrared solar absorption spectra of tropospheric HCN, C2H2, CO, and C2H6 have been recorded from the Network for the Detection of Stratospheric Change station in Lauder, New Zealand (45.04degreesS, 169.68degreesE, 0.37 km altitude). All four molecules were measured on over 350 days with HCN and C2H2 reported for the first time based on a new analysis procedure that significantly increases the effective signal-to-noise of weak tropospheric absorption features in the measured spectra. The CO measurements extend by 2.5 years a database of measurements begun in January 1994 for CO with improved sensitivity in the lower and middle troposphere. The C2H6 measurements lengthen a time series begun in July 1993 with peak sensitivity in the upper troposphere. Retrievals of all four molecules were obtained with an algorithm based on the semiempirical application of the Rodgers optimal estimation technique. Columns are reported for the 0.37- to 12-km-altitude region, approximately the troposphere above the station. The seasonal cycles of all four molecules are asymmetric, with minima in March-June and sharp peaks and increased variability during August-November, which corresponds to the period of maximum biomass burning near the end of the Southern Hemisphere tropical dry season. Except for a possible HCN column decrease, no evidence was found for a statistically significant long-term trend. [less ▲]

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