MLS Research

Chorine and Bromine Chemistry

Contact Lucien Froidevaux

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) See also the MLS website information regarding Global Ozone and Polar Ozone.

Latest Publications (Chlorine and Bromine)

  1. Solomon, S., K. Stone, P. Yu, D.M. Murphy, D. Kinnison, A.R. Ravishankara and P. Wang
    Chlorine activation and enhanced ozone depletion induced by wildfire aerosol
  2. Wang, P., S. Solomon and K. Stone
    Stratospheric chlorine processing after the 2020 Australian wildfires derived from satellite data
    Proc. Nat. Acad. Sci. doi:10.1073/pnas.2213910120, 2023
  3. Fujiwara, M., G.L. Manney, L.J. Gray and J.S. Wright
    SPARC Reanalysis Intercomparison Project S-RIP Final Report
    n/a 2022
  4. Santee, M.L., A. Lambert, G.L. Manney, N.J. Livesey, L. Froidevaux, J.L. Neu, M.J. Schwartz, L.F. Millán, F. Werner, W.G. Read, M. Park, R.A. Fuller and B.M. Ward
    Prolonged and Pervasive Perturbations in the Composition of the Southern Hemisphere Midlatitude Lower Stratosphere From the Australian New Year's Fires
    Geophys. Res. Lett. doi:10.1029/2021gl096270, 2022
  5. Blunden, J. and T. Boyer
    State of the Climate in 2020
    Bull. Am. Meteorol. Soc. doi:10.1175/2021bamsstateoftheclimate.1, 2021
  6. Han, Y., F. Xie and J. Zhang
    Has Stratospheric HCl in the Northern Hemisphere Been Increasing Since 2005?
    Front. Earth Sci. doi:10.3389/feart.2020.609411, 2020
  7. Nedoluha, G., R.M. Gomez, I. Boyd, H. Neal, A. Parrish, B. Connor, T. Mooney, D. Siskind, H. Sagawa and M. Santee
    Initial Results and Diurnal Variations Measured by a new Microwave Stratospheric ClO Instrument at Mauna Kea
    Journal of Geophysical Research: Atmospheres doi:10.1029/2020jd033097, 2020
  8. Johansson, S., M. Santee, J. Grooß, M. Höpfner, M. Braun, F. Friedl-Vallon, F. Khosrawi, O. Kirner, E. Kretschmer, H. Oelhaf, J. Orphal, B. Sinnhuber, I. Tritscher, J. Ungermann, K. Walker and W. Woiwode
    Unusual chlorine partitioning in the 2015/16 Arctic winter lowermost stratosphere: observations and simulations
    Atmos. Chem. Phys. doi:10.5194/acp-19-8311-2019, 2019
  9. Bernath, P. and A. Fernando
    Trends in stratospheric HCl from the ACE satellite mission
    J. Quant. Spectrosc. Radiat. Transfer doi:10.1016/j.jqsrt.2018.05.027, 2018
  10. Dhomse, S., D. Kinnison, M. Chipperfield, R. Salawitch, I. Cionni, M. Hegglin, N.L. Abraham, H. Akiyoshi, A. Archibald, E. Bednarz, S. Bekki, P. Braesicke, N. Butchart, M. Dameris, M. Deushi, S. Frith, S. Hardiman, B. Hassler, L. Horowitz, R. Hu, P. Jöckel, B. Josse, O. Kirner, S. Kremser, U. Langematz, J. Lewis, M. Marchand, M. Lin, E. Mancini, V. Marécal, M. Michou, O. Morgenstern, F. O&ampaposConnor, L. Oman, G. Pitari, D. Plummer, J. Pyle, L. Revell, E. Rozanov, R. Schofield, A. Stenke, K. Stone, K. Sudo, S. Tilmes, D. Visioni, Y. Yamashita and G. Zeng
    Estimates of ozone return dates from Chemistry-Climate Model Initiative simulations
    Atmos. Chem. Phys. doi:10.5194/acp-18-8409-2018, 2018
  11. Anderson, J., D. Weisenstein, K. Bowman, C. Homeyer, J. Smith, D. Wilmouth, D. Sayres, J.E. Klobas, S. Leroy, J. Dykema and S. Wofsy
    Stratospheric ozone over the United States in summer linked to observations of convection and temperature via chlorine and bromine catalysis
    Proc. Nat. Acad. Sci. doi:10.1073/pnas.1619318114, 2017
  12. Hegglin, M., S. Tegtmeier, J. Anderson, A. Bourassa, S. Brohede, D. Degenstein, L. Froidevaux, B. Funke, J. Gille, A. Jones, Y. Kasai, E. Kyrola, J. Lumpe, J. Neu, E. Remsberg, A. Rozanov, M. Toohey, J. Urban, T. von Clarmann, K.A. Walker and R. Wang
    The SPARC Data Initiative: Assessment of stratospheric trace gas and aerosol climatologies from satellite limb sounders
  13. Stone, K., S. Solomon, D. Kinnison, M. Pitts, L. Poole, M. Mills, A. Schmidt, R. Neely, D. Ivy, M. Schwartz, J. Vernier, B. Johnson, M. Tully, A. Klekociuk, G. König-Langlo and S. Hagiya
    Observing the impact of Calbuco volcanic aerosols on South Polar ozone depletion in 2015
    Journal of Geophysical Research: Atmospheres doi:10.1002/2017jd026987, 2017
  14. Nedoluha, G., B. Connor, T. Mooney, J. Barrett, A. Parrish, R.M. Gomez, I. Boyd, D. Allen, M. Kotkamp, S. Kremser, T. Deshler, P. Newman and M. Santee
    20 years of ClO measurements in the Antarctic lower stratosphere
    Atmos. Chem. Phys. doi:10.5194/acp-16-10725-2016, 2016
  15. Siskind, D., G. Nedoluha, F. Sassi, P. Rong, S. Bailey, M. Hervig and C. Randall
    Persistence of upper stratospheric wintertime tracer variability into the Arctic spring and summer
    Atmos. Chem. Phys. doi:10.5194/acp-16-7957-2016, 2016
  16. Manney, G., Z. Lawrence, M. Santee, W. Read, N. Livesey, A. Lambert, L. Froidevaux, H. Pumphrey and M. Schwartz
    A minor sudden stratospheric warming with a major impact: Transport and polar processing in the 2014/2015 Arctic winter
    Geophys. Res. Lett. doi:10.1002/2015gl065864, 2015
  17. Damiani, A., B. Funke, M.L. Puertas, A. Gardini, T. von Clarmann, M.L. Santee, L. Froidevaux and R.R. Cordero
    Changes in the composition of the northern polar upper stratosphere in February 2009 after a sudden stratospheric warming
    Journal of Geophysical Research: Atmospheres doi:10.1002/2014JD021698, 2014
  18. Strahan, S.E., A.R. Douglass, P.A. Newman and S.D. Steenrod
    Inorganic chlorine variability in the Antarctic vortex and implications for ozone recovery
    Journal of Geophysical Research: Atmospheres doi:10.1002/2014JD022295, 2014
  19. Khosravi, M., P. Baron, J. Urban, L. Froidevaux, A.I. Jonsson, Y. Kasai, K. Kuribayashi, C. Mitsuda, D.P. Murtagh, H. Sagawa, M.L. Santee, T.O. Sato, M. Shiotani, M. Suzuki, T. von Clarmann, K.A. Walker and S. Wang
    Diurnal variation of stratospheric and lower mesospheric HOCl, ClO and HO2 at the equator: comparison of 1-D model calculations with measurements by satellite instruments
    Atmos. Chem. Phys. doi:10.5194/acp-13-7587-2013, 2013
  20. Sagawa, H., T.O. Sato, P. Baron, E. Dupuy, N. Livesey, J. Urban, T. von Clarmann, A.D. Lange, G. Wetzel, B.J. Connor, A. Kagawa, D. Murtagh and Y. Kasai
    Comparison of SMILES ClO profiles with satellite, balloon-borne and ground-based measurements
    Atmospheric Measurement Techniques doi:10.5194/amt-6-3325-2013, 2013
  21. Wohltmann, I., T. Wegner, R. Mueller, R. Lehmann, M. Rex, G.L. Manney, M.L. Santee, P. Bernath, O. Suminska-Ebersoldt, F. Strohl, M. von Hobe, C.M. Volk, E. Hoesen, F. Ravegnani, A. Ulanovsky and V. Yushkov
    Uncertainties in modelling heterogeneous chemistry and Arctic ozone depletion in the winter 2009/2010
    Atmos. Chem. Phys. doi:10.5194/acp-13-3909-2013, 2013
  22. Damiani, A., B. Funke, D.R. Marsh, M. Lopez-Puertas, M.L. Santee, L. Froidevaux, S. Wang, C.H. Jackman, T. von Clarmann, A. Gardini, R.R. Cordero and M. Storini
    Impact of January 2005 solar proton events on chlorine species
    Atmos. Chem. Phys. doi:10.5194/acp-12-4159-2012, 2012
  23. Millan, L., N.J. Livesey, L. Froidevaux, D. Kinnison, R. Harwood, I.A. MacKenzie and M.P. Chipperfield
    New Aura Microwave Limb Sounder observations of BrO and implications for Bry
    Atmospheric Measurement Techniques doi:10.5194/amt-5-1741-2012, 2012
  24. Wegner, T., J.U. Grooss, M. von Hobe, F. Stroh, O. Suminska-Ebersoldt, C.M. Volk, E. Hosen, V. Mitev, G. Shur and R. Mueller
    Heterogeneous chlorine activation on stratospheric aerosols and clouds in the Arctic polar vortex
    Atmos. Chem. Phys. doi:10.5194/acp-12-11095-2012, 2012
  25. Nedoluha, G.E., B.J. Connor, J. Barrett, T. Mooney, A. Parrish, I. Boyd, J.E. Wrotny, R.M. Gomez, J. Koda, M.L. Santee and L. Froidevaux
    Ground-based measurements of ClO from Mauna Kea and intercomparisons with Aura and UARS MLS
    J. Geophys. Res. doi:10.1029/2010JD014732, 2011
  26. Froidevaux, L., Y.B. Jiang, A. Lambert, N.J. Livesey, W.G. Read, J.W. Waters, R.A. Fuller, T.P. Marcy, P.J. Popp, R.S. Gao, D.W. Fahey, K.W. Jucks, R.A. Stachnik, G.C. Toon, L.E. Christensen, C.R. Webster, P.F. Bernath, C.D. Boone, K.A. Walker, H.C. Pumphrey, R.S. Harwood, G.L. Manney, M.J. Schwartz, W.H. Daffer, B.J. Drouin, R.E. Cofield, D.T. Cuddy, R.F. Jarnot, B.W. Knosp, V.S. Perun, W.V. Snyder, P.C. Stek, R.P. Thurstans and P.A. Wagner
    Validation of Aura Microwave Limb Sounder HCl measurements
    J. Geophys. Res. doi:10.1029/2007JD009025, 2008
  27. Lary, D.J. and O. Aulov
    Space-based measurements of HCl: Intercomparison and historical context
    J. Geophys. Res. doi:10.1029/2007JD008715, 2008
  28. McConnell, J.C. and J.J. Jin
    Stratospheric Ozone Chemistry
    Atmosphere-Ocean doi:10.3137/ao.460104, 2008
  29. Santee, M.L., I.A. MacKenzie, G.L. Manney, M.P. Chipperfield, P.F. Bernath, K.A. Walker, C.D. Boone, L. Froidevaux, N.J. Livesey and J.W. Waters
    A study of stratospheric chlorine partitioning based on new
    J. Geophys. Res. doi:10.1029/2007JD009057, 2008
  30. Santee, M.L., A. Lambert, W.G. Read, N.J. Livesey, G.L. Manney, R.E. Cofield, D.T. Cuddy, W.H. Daffer, B.J. Drouin, L. Froidevaux, R.A. Fuller, R.F. Jarnot, B.W. Knosp, V.S. Perun, W.V. Snyder, P.C. Stek, R.P. Thurstans, P.A. Wagner, J.W. Waters, B. Connor, J. Urban, D. Murtagh, P. Ricaud, B. Barrett, A. Kleinboehl, J. Kuttippurath, H. Kullmann, M. von Hobe, G.C. Toon and R.A. Stachnik
    Validation of the Aura Microwave Limb Sounder ClO Measurements
    J. Geophys. Res. doi:10.1029/2007JD008762, 2008
  31. Kovalenko, L.J., K.W. Jucks, R.J. Salawitch, G.C. Toon, J-F. Blavier, D.G. Johnson, A. Kleinbohl, N.J. Livesey, J.J. Margitan, H.M. Pickett, M.L. Santee, B. Sen, R.A. Stachnik and J.W. Waters
    Observed and Modeled HOCl Profiles in the Midlatitude Stratosphere: Implication for Ozone Loss
    Geophys. Res. Lett. doi:10.1029/2007GL031100, 2007
  32. Kovalenko, L.J., N.J. Livesey, R.J. Salawitch, C. Camy-Peyret, M.P. Chipperfield, R.E. Cofield, M. Dorf, B.J. Drouin, L. Froidevaux, R.A. Fuller, F. Goutail, R.F. Jarnot, K. Jucks, B.W. Knosp, A. Lambert, I.A. MacKenzie, K. Pfeilsticker, J-P. Pommereau, W.G. Read, M.L. Santee, M.J. Schwartz, W.V. Snyder, R. Stachnik, P.C. Stek, P.A. Wagner and J.W. Waters
    Validation of the Aura Microwave Limb Sounder BrO observations in the stratosphere
    J. Geophys. Res. doi:10.1029/2007JD008817, 2007
  33. Lary, D.J., D.W. Waugh, A.R. Douglass, R.S. Stolarski, P.A. Newman and H. Mussa
    Variations in Stratospheric Inorganic Chlorine Between 1991 and 2006
    Geophys. Res. Lett. doi:10.1029/2007GL030053, 2007
  34. Manney, G.L., W.H. Daffer, J.M. Zawodny, P.F. Bernath, K.W. Hoppel, K.A. Walker, B.W. Knosp, C. Boone, E.E. Remsberg, M.L. Santee, V. Lynn Harvey, S. Pawson, D.R. Jackson, L. Deaver, C.T. McElroy, C.A. McLinden, J.R. Drummond, H.C. Pumphrey, A. Lambert, M.J. Schwartz, L. Froidevaux, S. McLeod, L.L. Takacs, M.J. Suarez, C.R. Trepte, D.T. Cuddy, N.J. Livesey, R.S. Harwood and J.W. Waters
    Solar Occultation Satellite Data and Derived Meteorological Products: Sampling Issues and Comparisons with Aura MLS
    J. Geophys. Res. doi:10.1029/2007JD008709, 2007
  35. Froidevaux, L., N.J. Livesey, W.G. Read, R.J. Salawitch, J.W. Waters, B.J. Drouin, I.A. MacKenzie, H.C. Pumphrey, P. Bernath, C. Boone, R. Nassar, S. Montzka, J. Elkins, D. Cunnold and D. Waugh
    Temporal decrease in upper atmospheric chlorine
    Geophys. Res. Lett. doi:10.1029/2006GL027600, 2006
  36. Livesey, N.J., L.J. Kovalenko, R.J. Salawitch, I.A. MacKenzie, M.P. Chipperfield, W.G. Read, R.F. Jarnot and J.W. Waters
    EOS Microwave Limb Sounder observations of upper stratospheric BrO: Implications for total bromine
    Geophys. Res. Lett. doi:10.1029/2006GL026930, 2006
  37. Nassar, R., P.F. Bernath, C.D. Boone, C. Clerbaux, P.F. Coheur, G. Dufour, L. Froidevaux, E. Mahieu, J.C. McConnell, S.D. McLeod, D.P. Murtagh, C.P. Rinsland, K. Semeniuk, R. Skelton, K.A. Walker and R. Zander
    A Global inventory of stratospheric chlorine in 2004 based on measurements by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS)
    J. Geophys. Res. doi:10.1029/2006JD007073, 2006
  38. Ricaud, P., P. Baron and J.D.L. Noë
    Quality assessment of ground-based microwave measurements of chlorine monoxide, ozone, and nitrogen dioxide from the NDSC radiometer at the Plateau de Bure
    Annales Geophysicae doi:10.5194/angeo-22-1903-2004, 2004
  39. Santee, M.L., G.L. Manney, J.W. Waters and N.J. Livesey
    Variations and climatology of ClO in the polar lower stratosphere from UARS MLS measurements
    J. Geophys. Res. doi:10.1029/2002JD003335, 2003
  40. Huang, F.T. and C.A. Reber
    Synoptic estimates of chemically active species and other diurnally varying parameters in the stratosphere, derived from measurements from the Upper Atmosphere Research Satellite (UARS)
    J. Geophys. Res. doi:10.1029/2000JD900515, 2001
  41. Feist, D.G., C.P. Aellig, N. Kampfer, P.M. Solomon, J.W. Barrett, S. Zoonematkermani, P. Hartogh, C. Jarchow and J.W. Waters
    Validation of stratospheric ClO from the Millimeter-wave Atmospheric Sounder (MAS)
    J. Geophys. Res. doi:10.1029/1999JD901175, 2000
  42. Froidevaux, L., J.W. Waters, W.G. Read, P.S. Connell, D.E. Kinnison and J.M. Russell III
    Variations in the free chlorine content of the stratosphere (1991-1997): Anthropogenic, volcanic, and methane influences
    J. Geophys. Res. doi:10.1029/1999JD901039, 2000
  43. Ricaud, P., M.P. Chipperfield, J.W. Waters, J.M. Russell III and A.E. Roche
    Temporal evolution of chlorine monoxide in the middle stratosphere
    J. Geophys. Res. doi:10.1029/1999JD900995, 2000
  44. Siskind, D.E., L. Froidevaux, J.M. Russell III and J. Lean
    Implications of upper stratospheric trace constituent changes observed by HALOE for O3 and ClO from 1992 to 1995
    Geophys. Res. Lett. doi:10.1029/98GL02664, 1998
  45. Waters, J.W.
    Atmospheric measurements by the MLS experiments: Results from UARS and plans for the future
    Adv. Space Res. doi:10.1016/S0273-1177(97)00744-8, 1998
  46. Osterman, G.B., R.J. Salawitch, B. Sen, G.C. Toon, R.A. Stachnik, H.M. Pickett, J.J. Margitan, J-F. Blavier and D.B. Peterson
    Balloon-borne measurements of stratospheric radicals and their precursors: Implications for the production and loss of ozone
    Geophys. Res. Lett. doi:10.1029/97GL00921, 1997
  47. Aellig, C.P., N. Kampfer, C. Rudin, R.M. Bevilacqua, W. Degenhardt, P. Hartogh, C. Jarchow, K. Kunzi, J.J. Olivero, C. Croskey, J.W. Waters and H.A. Michelsen
    Latitudinal distribution of upper stratospheric ClO as derived from space borne microwave spectroscopy
    Geophys. Res. Lett. doi:10.1029/96GL01215, 1996
  48. Chance, K., W.A. Traub, D.G. Johnson, K.W. Jucks, P. Ciarpallini, R.A. Stachnik, R.J. Salawitch and H.A. Michelsen
    Simultaneous measurements of stratospheric HOx, NOx and Clx: Comparsion with a photochemical model
    J. Geophys. Res. doi:10.1029/96JD00064, 1996
  49. Dessler, A.E., S.R. Kawa, A. Douglass, D.B. Considine, J.B. Kumer, A.E. Roche, J.W. Waters, J.M. Russell III and J.C. Gille
    A test of the partitioning between ClO and ClONO2 using simultaneous UARS measurements of ClO, NO2 and ClONO2
    J. Geophys. Res. doi:10.1029/96JD00695, 1996
  50. Dessler, A.E., S.R. Kawa, D.B. Considine, J.W. Waters, L. Froidevaux and J.B. Kumer
    UARS measurements of ClO and NO2 at 40 and 46 km and implications for the 'ozone deficit'
    Geophys. Res. Lett. doi:10.1029/96GL00154, 1996