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Chlorine and Bromine Chemistry
Contact: Lucien Froidevaux


Summary

Atmospheric measurements of chlorine and bromine compounds are important because chemically reactive chlorine and bromine species have been the major culprits involved in chemical ozone depletion over the past few decades. The source of chlorine and bromine compounds in the upper atmosphere is the release and slow decomposition of long-lived gases emitted at the Earth's surface, from (primarily) industrial products since the 1950s. The most striking consequence of these emissions was the discovery of an ozone hole over Antarctica in the early 1980s. Once the long-lived source gases (chlorofluorocarbons or CFCs, containing chlorine, and halons, containing bromine), used in refrigeration, aerosol propellants, foam material, solvents, dry cleaning, agriculture, or fire extinguishers, have been transported into the stratosphere (above about 15 km), they decompose, mainly from slow destruction by sunlight. This leads to reservoirs of chlorine (such as HCl, hydrogen chloride, measured by Aura MLS) and bromine (such as HBr), as well as more reactive ozone-depleting gases such as ClO (chlorine monoxide) and BrO (bromine monoxide), both measured by Aura MLS. Global measurements of ClO were also carried out from 1991 to 2000 by the Upper Atmosphere Research Satellite (UARS) MLS experiment; other very useful data have been provided by aircraft and ground-based measurements. A more minor species (HOCl, hypochlorous acid) is also measured by Aura MLS. The abundance of these gases is measured in amounts typically below a few parts per billion, down to parts per trillion, but the reactive radicals (ClO, BrO) can destroy ozone rapidly (at the rate of 1 percent/day in the lower stratosphere, during polar winter/spring) via catalytic reactions whereby one atom of chlorine (or bromine) can lead to the destruction of more than 100000 molecules of ozone. The total chlorine abundance at the Earth's surface has been decreasing since about 1993, and the sum of bromine abundances at the surface has decreased since the late 1990s. It is important to track the decrease (at a rate of about -0.5 to -1 %/yr) of total upper atmospheric chlorine (as seen in HCl near 50 km) as well as bromine; such measurements help to confirm the beneficial impact of the Montreal Protocol (which curtailed harmful surface emissions), and provide a database for comparison with atmospheric models and for improved projections of future change. For more specifics about chlorine and bromine scientific publications tied to the MLS observations, see the MLS publications list.

For an overview (targeted to the general public) of the impact of chlorine and bromine species on ozone destruction, see (for example) http://www.theozonehole.com/ozonedestruction.htm. See also the MLS website information regarding Global Ozone and Polar Ozone.

Relevant Pulbications

2011

  1. Nedoluha, G.E., "Ground-based measurements of ClO from Mauna Kea and intercomparisons with Aura and UARS MLS", vol doi:10.1029/2010JD014732, num 116, 2011. Reprint

2008

  1. Froidevaux, L., "Validation of Aura Microwave Limb Sounder HCl measurements", vol doi:10.1029/2007JD009025, num 113, 2008. Reprint
  2. Lary, D.J., "Space-based measurements of HCl: Intercomparison and historical context", vol doi:10.1029/2007JD008715, num 113, 2008. Reprint
  3. McConnell, J.C., "Stratospheric Ozone Chemistry", vol doi:10.3137/ao.460104, num 46, pgs. No. 1, 2008. Reprint
  4. Santee, M.L., "A study of stratospheric chlorine partitioning based on new", vol doi:10.1029/2007JD009057, num 113, 2008. Reprint
  5. Santee, M.L., "Validation of the Aura Microwave Limb Sounder ClO Measurements", vol doi:10.1029/2007JD008762, num 113, 2008. Reprint

2007

  1. Kovalenko, L.J., "Observed and Modeled HOCl Profiles in the Midlatitude Stratosphere: Implication for Ozone Loss", vol doi:10.1029/2007GL031100, num 34, 2007. Reprint
  2. Kovalenko, L.J., "Validation of the Aura Microwave Limb Sounder BrO observations in the stratosphere", vol doi:10.1029/2007JD008817, num 112, 2007. Reprint
  3. Lary, D.J., "Variations in Stratospheric Inorganic Chlorine Between 1991 and 2006", vol doi:10.1029/2007GL030053, num 34, 2007. Reprint
  4. Manney, G.L., "Solar Occultation Satellite Data and Derived Meteorological Products: Sampling Issues and Comparisons with Aura MLS", vol doi:10.1029/2007JD008709, num 112, 2007. Reprint

2006

  1. Froidevaux, L., "Temporal decrease in upper atmospheric chlorine", vol doi:10.1029/2006GL027600, num 33, 2006. Reprint Supplemental
  2. Livesey, N.J., "EOS Microwave Limb Sounder observations of upper stratospheric BrO: Implications for total bromine", vol doi:10.1029/2006GL026930, num 33, 2006. Reprint
  3. Nassar, R., "A Global inventory of stratospheric chlorine in 2004 based on measurements by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS)", vol doi:10.1029/2006JD007073, num 111, 2006. Reprint

2003

  1. Santee, M.L., "Variations and climatology of ClO in the polar lower stratosphere from UARS MLS measurements", vol doi:10.1029/2002JD003335, num 108, pgs. D15, 2003. Reprint Summary

2001

  1. Huang, F.T., "Synoptic estimates of chemically active species and other diurnally varying parameters in the stratosphere, derived from measurements from the Upper Atmosphere Research Satellite (UARS)", num 106, pgs. D2, 2001. Reprint

2000

  1. Feist, D.G., "Validation of stratospheric ClO from the Millimeter-wave Atmospheric Sounder (MAS)", num 105, pgs. D7, 2000. Reprint
  2. Froidevaux, L., "Variations in the free chlorine content of the stratosphere (1991-1997): Anthropogenic, volcanic, and methane influences", num 105, pgs. D4, 2000. Reprint
  3. Ricaud, P., "Temporal evolution of chlorine monoxide in the middle stratosphere", num 105, pgs. D4, 2000. Reprint

1998

  1. Siskind, D.E., "Implications of upper stratospheric trace constituent changes observed by HALOE for O3 and ClO from 1992 to 1995", num 25, 1998. Reprint
  2. Waters, J.W., "Atmospheric measurements by the MLS experiments: Results from UARS and plans for the future", num 21, 1998. Reprint

1997

  1. Osterman, G.B., "Balloon-borne measurements of stratospheric radicals and their precursors: Implications for the production and loss of ozone", num 24, 1997. Reprint

1996

  1. Aellig, C.P., "Latitudinal distribution of upper stratospheric ClO as derived from space borne microwave spectroscopy", num 23, 1996. Reprint
  2. Chance, K., "Simultaneous measurements of stratospheric HOx, NOx and Clx: Comparsion with a photochemical model", num 101, pgs. D4, 1996. Reprint
  3. Dessler, A.E., "A test of the partitioning between ClO and ClONO2 using simultaneous UARS measurements of ClO, NO2 and ClONO2", num 101, pgs. D7, 1996. Reprint
  4. Dessler, A.E., "UARS measurements of ClO and NO2 at 40 and 46 km and implications for the 'ozone deficit'", num 23, 1996. Reprint
  5. Waters, J.W., "Validation of UARS Microwave Limb Sounder ClO measurements", num 101, pgs. D6, 1996. Reprint

1995

  1. Crewell, S., "Comparison of ClO measurements made by airborne and spaceborne microwave radiometers in the Arctic winter stratosphere 1993", num 22, 1995. Reprint
  2. Dessler, A.E., "Correlated observations of HCl and ClONO2 from UARS and implications for stratospheric chlorine partitioning", num 22, 1995. Reprint
  3. Eckman, R.S., "Stratospheric trace constituents simulated by a three-dimensional general circulation model: Comparison with UARS data", num 100, pgs. D7, 1995. Reprint
  4. Johnson, D.G., "Estimating the abundance of ClO from simultaneous remote sensing measurements of stratospheric HOx, NOx and Clx", num 22, 1995. Reprint

1993

  1. Geller, M.A., "3-D transport-chemistry studies of the stratosphere using satellite data together with data assimilation", 1993.
  2. Waters, J.W., "The chlorine threat to stratospheric ozone", num LVI, 1993.

1992

  1. Stachnik, R.A., "Submillimeterwave heterodyne measurements of stratospheric ClO, HCl, O3, and HO2: First results", num 19, 1992. Reprint

1988

  1. Waters, J.W., "ClO and O3 stratospheric profiles: Balloon microwave measurements", num 15, 1988. Reprint

1981

  1. Waters, J.W., "Chlorine monoxide radical, ozone, and hydrogen peroxide: Stratospheric measurements by microwave limb sounding", num 214, 1981. Reprint

1979

  1. Waters, J.W., "Aircraft search for millimeter wavelength emission by stratospheric ClO", num 84, 1979. Reprint


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