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The MLS OH Product

Contact: Luis Millan

Basic Information

OH is one of the most chemically-active, and important, molecules in atmospheric chemistry. It is known for its role in controlling middle atmospheric ozone through catalytic reaction cycles that effectively destruct ozone.

OH is mainly produced through photochemistry in the UV region. The primary OH source in the stratosphere is ozone photolysis followed by the reaction with water vapor. In the mesosphere, direct water vapor photolysis is a major OH source. Due to its short chemical lifetime, OH is generally not affect by transport. It responds rapidly to changes in solar UV radiation and displays diurnal, seasonal, latitudinal, and solar cycle variabilities.

The OH Molecule
OH molecule visualzation

How it is part of MLS Science Objectives

MLS makes the first global measurements of OH during both day and night, which provides needed new information on middle atmospheric hydrogen chemistry that affects ozone. Lack of long-term global OH measurements has previously been a major limitation in constraining models of stratospheric chemistry. MLS OH measurements make it possible to study the global distribution and variability of OH, to provide observational evidence of OH response to solar cycle, to pinpoint the altitudes of the distinct nighttime OH layer, and to directly investigate OH changes and impacts during solar energetic particle (SEP) events.

How EOS MLS measures OH

The standard product for OH is taken from the 2.5 THz retrieval. OH has been validated using the balloon-borne FIRS-2 and BOH instruments (for vertical profile shape) [Pickett et al., 2006, 2008] and the ground-based FTUVS instrument (for long-term column variability) [Wang et al., 2008]. The continuous MLS OH data cover from Aug 2004 to Dec 2009. Due to its aging process, the THz sub-instrument of MLS has been in standby mode most of the time after Dec 2009. OH measurements have been limited to one 30-day measurement each year since 2011.

Retrieved concentrations of OH in the mesosphere are sometimes negative with estimated precisions that are much smaller than the size of the negative excursion. These negative concentrations are likely due to subtle inadequacies in the forward model or due to non-linearities in the retrieval. Positive concentrations in levels adjacent to negative concentrations are likely to overestimate the actual OH concentration, which often lead to a "zig-zag" feature in mesospheric OH vertical profiles.

Sample OH retrieval

OH Information from the Spectroscopy Database

Quick Product Information for data version v4.2

  • Swath Name: OH
  • Status Flag: Only use profiles for which the Status field is an even number.
  • Useful Range: 32-0.0032 hPa
  • DAAC Short Name: ML2OH
  • Precision: Only use values for which the estimated precision is a positive number.
  • Quality Threshold: MLS v4.2x OH data can be used irrespective of the value of the Quality field.
  • Convergence Threshold: <1.1

Download EOS Aura MLS OH v4.2 data

Publications related to the MLS OH data product


  1. Arsenovic, P., A. Damiani, E. Rozanov, B. Funke, A. Stenke, T. Peter, "Reactive nitrogen NOy and ozone responses to energetic electron precipitation during Southern Hemisphere winter", Atmospheric Chemistry and Physics 19, 14, 9485-9494, doi:10.5194/acp-19-9485-2019, 2019. reprint
  2. Zawedde, A., H.N. Tyssøy, J. Stadsnes, M. Sandanger, "Are EEP Events Important for the Tertiary Ozone Maximum?", Journal of Geophysical Research: Space Physics 124, 7, 5976-5994, doi:10.1029/2018ja026201, 2019. reprint


  1. Kulikov, M., A. Nechaev, M. Belikovich, T. Ermakova, A. Feigin, "Technical note: Evaluation of the simultaneous measurements of mesospheric OH, HO<sub>2</sub>, and O<sub>3</sub> under a photochemical equilibrium assumption – a statistical approach", Atmospheric Chemistry and Physics 18, 10, 7453-7471, doi:10.5194/acp-18-7453-2018, 2018. reprint
  2. Zawedde, A., H.N. Tyssøy, J. Stadsnes, M. Sandanger, "The Impact of Energetic Particle Precipitation on Mesospheric OH - Variability of the Sources and the Background Atmosphere", Journal of Geophysical Research: Space Physics 123, 7, 5764-5789, doi:10.1029/2017ja025038, 2018. reprint


  1. 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, R. Wang, "The SPARC Data Initiative: Assessment of stratospheric trace gas and aerosol climatologies from satellite limb sounders", SPARC Report 8,, 2017. reprint
  2. Li, K., Q. Zhang, S. Wang, S. Sander, Y. Yung, "Resolving the Model-Observation Discrepancy in the Mesospheric and Stratospheric HOx Chemistry", Earth and Space Science, doi:10.1002/2017ea000283, 2017. reprint
  3. Santee, M.L., G.L. Manney, N.J. Livesey, M.J. Schwartz, J.L. Neu, W.G. Read, "A comprehensive overview of the climatological composition of the Asian summer monsoon anticyclone based on 10 years of Aura Microwave Limb Sounder measurements", Journal of Geophysical Research: Atmospheres 122, doi:10.1002/2016jd026408, 2017. reprint


  1. Andersson, M.E., P.T. Verronen, D.R. Marsh, S.M. Paivarinta, J.M.C. Plane, "WACCM-D-Improved modeling of nitric acid and active chlorine during energetic particle precipitation", Journal of Geophysical Research: Atmospheres 121, 17, 10,328-10,341, doi:10.1002/2015jd024173, 2016. reprint
  2. Verkhoglyadova, O.P., J.M. Wissing, S. Wang, M.B. Kallenrode, G.P. Zank, "Nighttime mesospheric hydroxyl enhancements during SEP events and accompanying geomagnetic storms: Ionization rate modeling and Aura satellite observations", Journal of Geophysical Research: Space Physics 121, 7, 6017-6030, doi:10.1002/2015ja022217, 2016. reprint
  3. Zawedde, A., H.N. Tyssøy, R. Hibbins, P. Espy, L. Ødegaard, M. Sandanger, J. Stadsnes, "The impact of energetic electron precipitation on mesospheric hydroxyl during a year of solar minimum", Journal of Geophysical Research: Space Physics 121, 6, 5914-5929, doi:10.1002/2016ja022371, 2016. reprint


  1. Fytterer, T., M.L. Santee, M. Sinnhuber, S. Wang, " The 27 day solar rotational effect on mesospheric nighttime OH and O3 observations induced by geomagnetic activity", Journal of Geophysical Research: Space Physics 120, doi:10.1002/2015ja021183, 2015. reprint
  2. Sonkaew, T., R. Macatangay, "Determining relationships and mechanisms between tropospheric ozone column concentrations and tropical biomass burning in Thailand and its surrounding regions", Environmental Research Letters 10, 6, 065009, doi:10.1088/1748-9326/10/6/065009, 2015. reprint


  1. Andersson, M.E., P.T. Verronen, C.J. Rodger, M.A. Clilverd, S. Wang, "Longitudinal hotspots in the mesospheric OH variations due to energetic electron precipitation.", Atmospheric Chemistry and Physics 14, 2, 1095-1105, doi:10.5194/acp-14-1095-2014, 2014. reprint
  2. Hassler, B., I. Petropavlovskikh, J. Staehelin, T. August, P.K. Bhartia, C. Clerbaux, D. Degenstein, M.D. Mazière, B.M. Dinelli, A. Dudhia, G. Dufour, S.M. Frith, L. Froidevaux, S. Godin-Beekmann, J. Granville, N.R.P. Harris, K. Hoppel, D. Hubert, Y. Kasai, M.J. Kurylo, E. Kyrölä, J.C. Lambert, P.F. Levelt, C.T. McElroy, R.D. McPeters, R. Munro, H. Nakajima, A. Parrish, P. Raspollini, E.E. Remsberg, K.H. Rosenlof, A. Rozanov, T. Sano, Y. Sasano, M. Shiotani, H.G.J. Smit, G. Stiller, J. Tamminen, D.W. Tarasick, J. Urban, R.J.d. van A, J.P. Veefkind, C. Vigouroux, T. von Clarmann, C. von Savigny, K.A. Walker, M. Weber, J. Wild, J.M. Zawodny, "Past changes in the vertical distribution of ozone - Part 1: Measurement techniques, uncertainties and availability", Atmospheric Measurement Techniques 7, 5, 1395-1427, doi:10.5194/amt-7-1395-2014, 2014. reprint
  3. Verkhoglyadova, O.P., S. Wang, M.G. Mlynczak, L.A. Hunt, G.P. Zank, "Effects of two large solar energetic particle events on middle atmosphere nighttime odd hydrogen and ozone content: Aura/MLS and TIMED/SABER measurements", Journal of Geophysical Research - Space Physics 120, doi:10.1002/2014JA020609, 2014. reprint
  4. Verkhoglyadova, O.P., S. Wang, "Middle Atmosphere Response to Large SEP Events: September 2005 Event", Outstanding Problems in Heliophysics: From Coronal Heating to the Edge of the Heliosphere 484, 216, 2014.


  1. Shapiro, A.V., E.V. Rozanov, A.I. Shapiro, T.A. Egorova, J. Harder, M. Weber, A.K. Smith, W. Schmutz, T. Peter, "The role of the solar irradiance variability in the evolution of the middle atmosphere during 2004-2009", Journal of Geophysical Research 118, 9, 3781-3793, doi:10.1002/jgrd.50208, 2013. reprint
  2. 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, F.P. Mills, "Midlatitude atmospheric OH response to the most recent 11-y solar cycle", Proceedings of the National Academy of Sciences 110, 6, 2023-2028, doi:10.1073/pnas.1117790110, 2013. reprint


  1. Andersson, M.E., P.T. Verronen, S. Wang, C.J. Rodger, M.A. Clilverd, B.R. Carson, "Precipitating radiation belt electrons and enhancements of mesospheric hydroxyl durign 2004-2009", Journal of Geophysical Research 117, D09304, doi:10.1029/2011JD017246, 2012. reprint
  2. Shapiro, A.V., E. Rozanov, A.I. Shapiro, S. Wang, T. Egorova, W. Schmutz, Th. Peter, "Signature of the 27-day solar rotation cycle in mesospheric OH and H2O observed by the Aura Microwave Limb Sounder", Atmospheric Chemistry and Physics 12, 3181-3188, doi:10.5194/acp-12-3181-2012, 2012. reprint


  1. Jackman, C.H., D.R. Marsh, F.M. Vitt, R.G. Roble, C.E. Randall, P.F. Bernath, B. Funke, M. Lopez-Puertas, S. Versick, G.P. Stiller, A.J. Tylka, E.L. Flemming, "Northern Hemisphere atmospheric influence of the solar proton events and ground level enhancement in January 2005", Atmospheric Chemistry and Physics 11, 6153-6166, doi:10.5194/acp-11-6153-2011, 2011. reprint
  2. Minschwaner, K.R., G.L. Manney, S.H. Wang, R.S. Harwood, "Hydroxyl in the stratosphere and mesosphere - Part 1: Diurnal variability", Atmospheric Chemistry and Physics 11, 955-962, doi:10.5194/acp-11-955-2011, 2011. reprint
  3. Sovde, O.A., Y.J. Orsolini, D.R. Jackson, F. Stordal, I.S.A. Isaksen, B. Rognerud, "Estimation of Arctic O3 loss during winter 2006/2007 using data assimilation and comparison with a chemical transport model", Quarterly Journal of the Royal Meteorological Society, doi:10.1002/qj.740, 2011. reprint
  4. Verronen, P.T., C.J. Rodger, M.A. Clilverd, S.H. Wang, "First evidence of mesospheric hydroxyl response to electron precipitation from the radiation belts", Journal of Geophysical Research 116, D07307, doi:10.1029/2010JD014965, 2011. reprint
  5. Wu, L., H. Su, J.H. Jiang, "Regional simulations of deep convection and biomass burning over South America: 1. Model evaluations using multiple satellite data sets", Journal of Geophysical Research 116, D17208, doi:10.1029/2011JD016105, 2011. reprint


  1. Damiani, A., M. Storini, C. Rafanelli, P. Diego, "The hydroxyl radical as an indicator of SEP fluxes in the high-latitude terrestrial atmosphere", Advances in Space Research 46, 9, 1225-1235, doi:10.1016/j.asr.2010.06.022, 2010. reprint
  2. Damiani, A., M. Storini, M.L. Santee, S. Wang, "Variability of the nighttime OH layer and mesospheric ozone at high latitudes during northern winter: influence of meteorology", Atmospheric Chemistry and Physics 10, 10291-10303, doi:10.5194/acp-10-10291-2010, 2010. reprint
  3. Englert, C.R., M.H. Stevens, D.E. Siskind, J.M. Harlander, F.L. Roesler, "Spatial Heterodyne Imager for Meospheric Radicals on STPSat-1", Journal of Geophysical Research 115, D20306, doi:10.1029/2010JD014398, 2010. reprint
  4. Minschwaner, K., G.L. Manney, N.J. Livesey, H.C. Pumphrey, H.M. Pickett, L. Froidevaux, A. Lambert, M.J. Schwartz, P.F. Bernath, K.A. Walker, C.D. Boone, "The photochemistry of carbon monoxide in the stratosphere and mesosphere evaluated from observations by the Microwave Limb Sounder on the Aura satellite", Journal of Geophysical Research 115, D13303, doi:10.1029/2009JD012654, 2010. reprint
  5. Wargan, K., S. Pawson, I. Stajner, V. Thouret, "Spatial structure of assimilated ozone in the upper troposphere and lower stratosphere", Journal of Geophysical Research 115, D24316, doi:10.1029/2010JD013941, 2010. reprint


  1. Damiani, A., M. Storini, M. Laurenza, C. Rafanelli, "Solar particle effects on minor components of the Polar atmosphere", Annales Geophysicae 26, 2, 361-370, doi:10.5194/angeo-26-361-2008, 2008. reprint
  2. Englert, C.R., M.H. Stevens, D.E. Siskind, J.M. Harlander, F.L. Roesler, H.M. Pickett, C. von Savigny, A.J. Kochenash, "First results from the Spatial Heterodyne Imager for Mesospheric Radicals (SHIMMER): Diurnal variation of mesospheric hydroxyl", Geophysical Research Letters 35, L19813, doi:10.1029/2008GL035420, 2008. reprint
  3. 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, K. Minschwaner, "Validation of Aura Microwave Limb Sounder OH and HO2 measurements", Journal of Geophysical Research 113, D16S30, doi:10.1029/2007JD008775, 2008. reprint
  4. Roesevall, J.D., D.P. Murtagh, J. Urban, W. Feng, P. Eriksson, S. Brohede, "A study of ozone depletion in the 2004/2005 Arctic winter based on data from Odin/SMR and Aura/MLS", Journal of Geophysical Research 113, D13301, doi:10.1029/2007JD009560, 2008. reprint
  5. 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, 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", Journal of Geophysical Research 113, D22301, doi:10.1029/2008JD009883, 2008. reprint


  1. Hocke, K., N. Kampfer, D. Ruffieux, L. Froidevaux, A. Parrish, I. Boyd, T. von Clarmann, T. Steck, Y.M. Timofeyev, A.V. Polyakov, E. Kyrola, "Comparison and synergy of stratospheric ozone measurements by satellite limb sounders and the ground-based microwave radiometer SOMORA", Atmospheric Chemistry and Physics 7, 4117-4131, doi:10.5194/acp-7-4117-2007, 2007. reprint
  2. Mueller, E.R., R. Henschke, W.E. Robotham, L.A. Newman, L.M. Laughman, R.A. Hart, J. Kennedy, H.M. Pickett, "Terahertz local oscillator for the Microwave Limb Sounder on the Aura Satellite", Applied Optics 46, no. 22, 4907-4915, doi:10.1364/AO.46.004907, 2007. reprint
  3. Verronen, P.T., C.J. Rodger, M.A. Clilverd, H.M. Pickett, E. Turunen, "Latitudinal extent of the January 2005 solar proton event in the Northern Hemisphere from satellite observations of hydroxyl", Annales Geophysicae 25, 2203-2215, doi:10.5194/angeo-25-2203-2007, 2007. reprint


  1. Canty, T., H.M. Pickett, R.J. Salawitch, K.W. Jucks, W.A. Traub, J.W. Waters, "Stratospheric and Mesospheric HOx: Results from Aura MLS and FIRS-2", Geophysical Research Letters 33, L12802, doi:10.1029/2006GL025964, 2006. reprint
  2. Pickett, H.M., "Microwave Limb Sounder THz Module on Aura", IEEE Transactions on Geoscience and Remote Sensing 44, 5 , 1122-1130, doi:10.1109/TGRS.2005.862667, 2006. reprint
  3. Pickett, H.M., W.G. Read, K.K. Lee, Y.L. Yung, "Observation of Night OH in the Mesosphere", Geophysical Research Letters 33, L19808, doi:10.1029/2006GL026910, 2006. reprint
  4. 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, W.A. Traub, "Validation of Aura MLS HOx measurements with remote-sensing balloon instruments", Geophysical Research Letters 33, L01808, doi:10.1029/2005GL024048, 2006. reprint
  5. Verronen, P.T., A. Seppala, E. Kyrola, J. Tamminen, H.M. Pickett, E. Turunen, "Production of Odd Hydrogen in the Mesosphere During the January 2005 Solar Proton Event", Geophysical Research Letters 33, L24811, doi:10.1029/2006GL028115, 2006. reprint


  1. Gaidis, M.C., H.M. Pickett, C.D. Smith, S.C. Martin, R.P. Smith, P.H. Siegel, "A 2.5-THz Receiver Front End for Spaceborne Applications", IEEE Transactions on Microwave Theory and Techniques 44, 733-739, doi:10.1109/THZ.1998.731652, 2000. reprint


  1. Pickett, H.M., D.B. Peterson, "Comparison of measured stratospheric OH with prediction", Journal of Geophysical Research 101, D11, 16789-16796, doi:10.1029/96JD01168, 1996. reprint

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