MLS Research

Hydrogen Chemistry

Contact Luis Millan

The odd-hydrogen radicals, OH and HO2 (collectively known as HOx), play fundamental roles in the middle atmospheric photochemistry due to their ability to destroy odd oxygen (O3 and O). In particular, at altitudes above ~40 km, the major catalytic O3 loss is controlled by reactions involving HOx species.

A better understanding of the trend in HOx thus helps to properly identify the recovery of the O3 layer. In this region of the atmosphere, HOx mainly come from the photolysis of O3 (i.e., the break down of O3 by sunlight) followed by reaction with H2O. In addition, chemical destruction of H2 and direct photolysis of H2O are also sources of HOx, especially above 80 km. The distribution of HOx species and the chemistry involved are sensitive to solar forcing such as the diurnal cycle, the seasonal cycle, the solar 11-year and 27-day cycles, and solar proton events (SPEs) .

Before the launch of Aura, the investigation of hydrogen chemistry had been greatly limited due to the lack of multi-year systematic observations on a global scale. The only available long-term records were a number of ground-based measurements of OH total column abundance. Large discrepancies among measurements and between model predictions and observations were reported.

MLS provides the first global daily measurements of HOx vertical profiles in the stratosphere and the mesosphere, making it possible to resolve some of these discrepancies, and significantly improve our understanding of the chemistry involved and the response to external forcing.

In particular, MLS observations will help to investigate the discrepancy between modeled and observed O3 in the upper stratosphere, known as the "O3 deficit", which implies that there could be a gap in the current understanding of hydrogen chemistry.

In addition, the magnitude of the solar effects on hydrogen chemistry is currently unclear, given the large discrepancies between observed and modeled response of O3 and OH to the solar cycle.

MLS-related publications concerning stratospheric and mesospheric hydrogen chemistry

  1. Nishiyama, T., M. Taguchi, H. Suzuki, P. Dalin, Y. Ogawa, U. Brändström and T. Sakanoi
    Temporal evolutions of N2 Meinel (1,2) band near 1.5µm associated with aurora breakup and their effects on mesopause temperature estimations from OH Meinel (3,1) band
    Earth, Planets and Space 10.1186/s40623-021-01360-0, 2021
  2. James, A., D. Moon, W. Feng, P. Lakey, V. Frankland, D. Heard and J. Plane
    The uptake of HO2 on meteoric smoke analogues
    Journal of Geophysical Research: Atmospheres doi:10.1002/2016jd025882, 2017
  3. Davis, S., K. Rosenlof, B. Hassler, D. Hurst, W. Read, H. Vömel, H. Selkirk, M. Fujiwara and R. Damadeo
    The Stratospheric Water and Ozone Satellite Homogenized SWOOSH database: a long-term database for climate studies
    Earth System Science Data doi:10.5194/essd-8-461-2016, 2016
  4. Rong, P.P., J.M. Russell, B.T. Marshall, D.E. Siskind, M.E. Hervig, L.L. Gordley, P.F. Bernath and K.A. Walker
    Version 1.3 AIM SOFIE measured methane CH4: Validation and seasonal climatology
    Journal of Geophysical Research: Atmospheres doi:10.1002/2016jd025415, 2016
  5. Zawedde, A., H.N. Tyssøy, R. Hibbins, P. Espy, L. Ødegaard, M. Sandanger and J. Stadsnes
    The impact of energetic electron precipitation on mesospheric hydroxyl during a year of solar minimum
    Journal of Geophysical Research: Space Physics doi:10.1002/2016ja022371, 2016
  6. Andersson, M.E., P.T. Verronen, C.J. Rodger, M.A. Clilverd and A. Seppala
    Missing driver in the Sun–Earth connection from energetic electron precipitation impacts mesospheric ozone
    Nature Communications doi:10.1038/ncomms6197, 2014
  7. 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
  8. Wang, S., K.F. Li, T.J. Pongetti, S.P. Sander, Y.L. Yung, M.C. Liang, N.J. Livesey, M.L. Santee, J.W. Harder, M. Snow and F.P. Mills
    Midlatitude atmospheric OH response to the most recent 11-y solar cycle
    Proc. Nat. Acad. Sci. doi:10.1073/pnas.1117790110, 2013
  9. Andersson, M.E., P.T. Verronen, S. Wang, C.J. Rodger, M.A. Clilverd and B.R. Carson
    Precipitating radiation belt electrons and enhancements of mesospheric hydroxyl durign 2004-2009
    J. Geophys. Res. doi:10.1029/2011JD017246, 2012
  10. Shapiro, A.V., E. Rozanov, A.I. Shapiro, S. Wang, T. Egorova, W. Schmutz and Th. Peter
    Signature of the 27-day solar rotation cycle in mesospheric OH and H2O observed by the Aura Microwave Limb Sounder
    Atmos. Chem. Phys. doi:10.5194/acp-12-3181-2012, 2012
  11. Verronen, P.T., C.J. Rodger, M.A. Clilverd and S.H. Wang
    First evidence of mesospheric hydroxyl response to electron precipitation from the radiation belts
    J. Geophys. Res. doi:10.1029/2010JD014965, 2011
  12. Dyrland, M.E., C.M. Hall, F.J. Mulligan and M. Tsutsumi
    Improved estimates for neutral air temperatures at 90 km and 78°N using satellite and meteor radar data
    Radio Science doi:10.1029/2009RS004344, 2010
  13. Englert, C.R., M.H. Stevens, D.E. Siskind, J.M. Harlander and F.L. Roesler
    Spatial Heterodyne Imager for Meospheric Radicals on STPSat-1
    J. Geophys. Res. doi:10.1029/2010JD014398, 2010
  14. Pickett, H.M., B.J. Drouin, T. Canty, R.J. Salawitch, R.A. Fuller, V.S. Perun, N.J. Livesey, J.W. Waters, R.A. Stachnik, S.P. Sander, W.A. Traub, K.W. Jucks and K. Minschwaner
    Validation of Aura Microwave Limb Sounder OH and HO2 measurements
    J. Geophys. Res. doi:10.1029/2007JD008775, 2008
  15. Wang, S., H.M. Pickett, T.J. Pongetti, R. Cheung, Y.L. Yung, C. Shim, Q. Li, T. Canty, R.J. Salawitch, K.W. Jucks, B. Drouin and S.P. Sander
    Validation of Aura Microwave Limb Sounder OH measurements with Fourier Transform Ultra-Violet Spectrometer total OH column measurements at Table Mountain, California
    J. Geophys. Res. doi:10.1029/2008JD009883, 2008
  16. 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
  17. Verronen, P.T., C.J. Rodger, M.A. Clilverd, H.M. Pickett and E. Turunen
    Latitudinal extent of the January 2005 solar proton event in the Northern Hemisphere from satellite observations of hydroxyl
    Annales Geophysicae doi:10.5194/angeo-25-2203-2007, 2007
  18. Canty, T., H.M. Pickett, R.J. Salawitch, K.W. Jucks, W.A. Traub and J.W. Waters
    Stratospheric and Mesospheric HOx: Results from Aura MLS and FIRS-2
    Geophys. Res. Lett. doi:10.1029/2006GL025964, 2006
  19. Pickett, H.M.
    Microwave Limb Sounder THz Module on Aura
    IEEE Trans. Geosci. Remote Sensing doi:10.1109/TGRS.2005.862667, 2006
  20. Pickett, H.M., W.G. Read, K.K. Lee and Y.L. Yung
    Observation of Night OH in the Mesosphere
    Geophys. Res. Lett. doi:10.1029/2006GL026910, 2006
  21. Pickett, H.M., B.J. Drouin, T. Canty, L.J. Kovalenko, R.J. Salawitch, N.J. Livesey, W.G. Read, J.W. Waters, K.W. Jucks and W.A. Traub
    Validation of Aura MLS HOx measurements with remote-sensing balloon instruments
    Geophys. Res. Lett. doi:10.1029/2005GL024048, 2006
  22. Verronen, P.T., A. Seppala, E. Kyrola, J. Tamminen, H.M. Pickett and E. Turunen
    Production of Odd Hydrogen in the Mesosphere During the January 2005 Solar Proton Event
    Geophys. Res. Lett. doi:10.1029/2006GL028115, 2006
  23. 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
  24. Pickett, H.M. and D.B. Peterson
    Comparison of measured stratospheric OH with prediction
    J. Geophys. Res. doi:10.1029/96JD01168, 1996
  25. Stachnik, R.A., J.C. Hardy, J.A. Tarsala, J.W. Waters and N.R. Erickson
    Submillimeterwave heterodyne measurements of stratospheric ClO, HCl, O3, and HO2: First results
    Geophys. Res. Lett. doi:10.1029/92GL01884, 1992