Long-term trends of inorganic chlorine from ground-based infrared solar spectra: Past increases and evidence for stabilization

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 ▲]

Controlled substances and other source gases, Chapter 1 of the Scientific Assessment of Ozone Depletion: 2002

in Nohende Ajavon, Ayité-Lô; Albritton, Daniel L.; Mégie, Gérard (Eds.) et al Scientific Assessment of Ozone Depletion: 2002 (2003)

This chapter provides an update on scientific progress since the previous Scientific Assessment of Ozone Depletion (WMO, 1999) regarding ozone-depleting substances (ODSs) in the atmosphere. This includes ... [more ▼]

This chapter provides an update on scientific progress since the previous Scientific Assessment of Ozone Depletion (WMO, 1999) regarding ozone-depleting substances (ODSs) in the atmosphere. This includes a discussion of the latest available data for observed trends in the troposphere and stratosphere, emissions, lifetimes, Ozone Depletion Potentials (ODPs), and Global Warming Potentials (GWPs). On the basis of this updated informaion, we relate observations of ODSs in the atmosphere to expectations, and discuss the evidence that the Montreal Protocol is effectively reducing ozone-depleting gases in the atmosphere. [less ▲]

Monitoring of the variability and long-term evolution of tropospheric constituents by Infrared solar absorption spectrometry at the Jungfraujoch, Switzerland.

in Borrell, P.; Borrell, P. M.; Burrows, J. P. (Eds.) et al Sounding the Troposphere from Space: A new era for Atmospheric Chemistry. (2003)

Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment version 3 data retrievals

in Applied Optics (2002), 41(33), 6968-6979

Version 3 of the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment data set for some 30 trace and minor gas profiles is available. From the IR solar-absorption spectra measured during four Space ... [more ▼]

Version 3 of the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment data set for some 30 trace and minor gas profiles is available. From the IR solar-absorption spectra measured during four Space Shuttle missions (in 1985, 1992, 1993, and 1994), profiles from more than 350 occultations were retrieved from the upper troposphere to the lower mesosphere. Previous results were unreliable for tropospheric retrievals, but with a new global-fitting algorithm profiles are reliably returned down to altitudes as low as 6.5 km (clouds permitting) and include notably improved retrievals of H2O, CO, and other species. Results for stratospheric water are more consistent across the ATMOS spectral filters and do not indicate a net consumption of H-2 in the upper stratosphere. A new sulfuric-acid aerosol product is described. An overview of ATMOS Version 3 processing is presented with a discussion of estimated uncertainties. Differences between these Version 3 and previously reported Version 2 ATMOS results are discussed. Retrievals are available at http://atmos.jpl.nasa.gov/atmos. (C) 2002 Optical Society of America. [less ▲]

Stratospheric HF column abundances above Kitt Peak (31.9 degrees N latitude): trends from 1977 to 2001 and correlations with stratospheric HCl columns

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 ▲]

ATMOS version 3 water vapor measurements: Comparisons with observations from two ER-2 Lyman-alpha hygrometers, MkIV, HALOE, SAGE II, MAS, and MLS

in Journal of Geophysical Research. Atmospheres (2002), 107(D3),

[1] We have compared a new version of Atmospheric Trace Molecule Spectroscopy Experiment (ATMOS) retrievals (version 3) of stratospheric and mesospheric water vapor with observations from shuttleborne ... [more ▼]

[1] We have compared a new version of Atmospheric Trace Molecule Spectroscopy Experiment (ATMOS) retrievals (version 3) of stratospheric and mesospheric water vapor with observations from shuttleborne, satelliteborne, balloonborne, and aircraftborne instruments. These retrievals show agreement to within 5% with the MkIV observations in the middle and lower stratosphere. ATMOS agrees with the National Oceanic and Atmospheric Administration (NOAA) Lyman-alpha hygrometer to within 5% except for features with spatial scales less than the vertical resolution of ATMOS (such as the lower stratospheric seasonal cycle). ATMOS observations are 10-16% lower than measurements from the Harvard Lyman-alpha hygrometer in the lower stratosphere and are 7-14% higher than those from the Microwave Limb Sounder (MLS; prototype version 0104) throughout most of the stratosphere. Agreement is within 7% with the Millimeter-Wave Atmospheric Sounder (MAS; version 20) in the middle and upper stratosphere, but differences are closer to 13% in the lower stratosphere. Throughout the stratosphere, agreement is within 8% with the Halogen Occultation Experiment (HALOE; version 19). ATMOS data from 1994 show agreement with the Stratospheric Aerosol and Gas Experiment II (SAGE II; version 6) values to within 8% in the middle stratosphere, but ATMOS observations are systematically higher than those from SAGE II by as much as 41% in the lower stratosphere. In contrast, ATMOS 1985 values are systematically similar to50% lower than SAGE II values from sunset occultations in the lower stratosphere near 70 hPa but appear to be in better agreement with sunrise occultations. Version 3 retrievals in the upper stratosphere and lower mesosphere are typically 5-10% lower than version 2 values between 1 and 0.05 hPa. This reduction improves agreement with HALOE, MAS, and MLS upper atmospheric observations, but ATMOS values still tend to be higher than values from these instruments in the middle mesosphere. Agreement among the instruments compared here (except for SAGE II) is generally within 15% in the middle to lower stratosphere and mesosphere and within 10% in the middle to upper stratosphere. At altitudes near 30 km, all instruments (including SAGE II) agree to within 10%. [less ▲]

Potential of the NDSC in support of the Kyoto Protocol: Examples from the station Jungfraujoch, Switzerland

in Van Ham, J.; Baede, A. P. M.; Guicherit, R. (Eds.) et al Non-CO2 Greenhouse Gases: Scientific Understanding, Control Options and Policy Aspects (2002)

This paper gives a brief description and “raison d’être” of the Network for the Detection of Stratospheric Change (NDSC) as well as its key research tasks to address the broader goal of monitoring ... [more ▼]

This paper gives a brief description and “raison d’être” of the Network for the Detection of Stratospheric Change (NDSC) as well as its key research tasks to address the broader goal of monitoring atmospheric changes and to identify their causes and related impacts on mankind’s environment. While the Network has primarily focussed, thus far, on monitoring the ozone layer and assessing global compliance with the Montreal Protocol, ongoing implementations and new capabilities have enabled it to adapt to more recent political developments such as the Kyoto Proto-col on substances affecting the climate system. Examples of activities in support of the latter are reported, based on infrared solar observations at the Jungfraujoch station. [less ▲]

Enhanced tropospheric HCN columns above Kitt Peak during the 1982-1983 and 1997-1998 El Nino warm phases

in Journal of Quantitative Spectroscopy & Radiative Transfer (2001), 69(1), 3-8

Free tropospheric HCN columns have been derived from infrared solar spectra recorded with the National Solar Observatory Fourier transform spectrometer on Kitt Peak, Arizona (31.9ºN latitude, 111.6ºW ... [more ▼]

Free tropospheric HCN columns have been derived from infrared solar spectra recorded with the National Solar Observatory Fourier transform spectrometer on Kitt Peak, Arizona (31.9ºN latitude, 111.6ºW longitude, 2.09 km altitude) between May 1978 and May 2000. The time series show up to a factor of 2.4 enhancement during the strong El Ninos of 1982-1983 and 1997-1998, the most intense since 1970. The observations provide confirmation that HCN is a sensitive tracer of biomass burning emissions transported to the free troposphere. No statistically significant long-term trend in the HCN-free tropospheric column has been detected over the 22-year measurement period. The results illustrate the importance of long-term spectroscopic measurements for quantifying climate and atmospheric chemistry-related atmospheric changes. [less ▲]

Free tropospheric CO, C2H6, and HCN above central Europe: Recent measurements from the Jungfraujoch station including the detection of elevated columns during 1998

in Journal of Geophysical Research. Atmospheres (2000), 105(D19), 24235-24249

Time series of free tropospheric carbon monoxide (CO), ethane (C2H6), and hydrogen cyanide (HCN) column abundances have been derived from observations at the International Scientific Station of the ... [more ▼]

Time series of free tropospheric carbon monoxide (CO), ethane (C2H6), and hydrogen cyanide (HCN) column abundances have been derived from observations at the International Scientific Station of the Jungfraujoch (ISSJ) at 3.58-km altitude in the Swiss Alps (latitude 46.55 degreesN, 7.98 degreesE longitude). The free troposphere was assumed to extend from 3.58 to 11 km altitude, and the related columns were derived for all three molecules from high spectral resolution infrared solar spectra recorded between January 1995 and October 1999. The three molecules show distinct seasonal cycles with maxima during winter for CO and C2H6, and during spring for HCN. These seasonal changes are superimposed on interannual variations. The tropospheric columns of all three molecules were elevated during 1998. Increases were most pronounced for HCN with enhanced values throughout the year, up to a factor of 2 in January 1998 when compared to averages of the other years. The increased tropospheric columns coincide with the period of widespread wildfires during the strong El Nino warm phase of 1997-1998. The emission enhancements above ISSJ are less pronounced, and they peaked after the increases measured above Mauna Loa (19.55 degreesN, 155.6 degreesW). Tropospheric trends for CO, C2H6, and HCN of (2.40 +/- 0.49), (0.47 +/- 0.64), and (7.00 +/- 1.61)% yr(-1)(1 sigma) were derived for January 1995 to October 1999. However, if 1998 measurements are excluded from the fit, CO and HCN trends that are not statistically significant, and a statistically significant decrease in the C2H6 tropospheric column, are inferred. Comparisons of the infrared CO columns with CO in situ surface measurements suggest that the CO free tropospheric vertical Volume mixing ratio profile generally decreases with altitude throughout the year. [less ▲]

Stratospheric CO at tropical and mid-latitudes: ATMOS measurements and photochemical steady-state model calculations

in Geophysical Research Letters (2000), 27(9), 1395-1398

We characterize the spring and fall stratospheric distribution of CO at 49 degrees N-55 degrees S latitude from ATMOS profiles measured during 4 shuttle flights, Measured mixing ratios increase with ... [more ▼]

We characterize the spring and fall stratospheric distribution of CO at 49 degrees N-55 degrees S latitude from ATMOS profiles measured during 4 shuttle flights, Measured mixing ratios increase with potential temperature (theta) from 12 ppbv (10(-9) per unit volume) at 525 K, to 30-40 ppbv at 1750 K with only minor variations with latitude and season at a theta level. Evidence for some confinement near 1150 K in the developing November 1994 vortex is indicated from comparison of CO and N2O horizontal gradients. Measured CO mixing ratios at the tropical tropopause are a factor of 10 higher than values calculated with a steady-state model using standard photochemistry constrained by correlative temperatures and pressures, and ATMOS measurements including CH4 as inputs, Differences decrease with latitude at constant theta and are <20% at 800 K and all latitudes, where the CO photochemical lifetime is 40-50 days. [less ▲]