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Strong correlation between levels of tropospheric hydroxyl radicals and solar ultraviolet radiation


The most important chemical cleaning agent of the atmosphere is the hydroxyl radical1,2, OH. It determines the oxidizing power of the atmosphere, and thereby controls the removal of nearly all gaseous atmospheric pollutants3,4. The atmospheric supply of OH is limited, however, and could be overcome by consumption due to increasing pollution and climate change4,5,6, with detrimental feedback effects. To date, the high variability of OH concentrations has prevented the use of local observations to monitor possible trends in the concentration of this species. Here we present and analyse long-term measurements of atmospheric OH concentrations, which were taken between 1999 and 2003 at the Meteorological Observatory Hohenpeissenberg in southern Germany. We find that the concentration of OH can be described by a surprisingly linear dependence on solar ultraviolet radiation throughout the measurement period, despite the fact that OH concentrations are influenced by thousands of reactants. A detailed numerical model of atmospheric reactions and measured trace gas concentrations indicates that the observed correlation results from compensations between individual processes affecting OH, but that a full understanding of these interactions may not be possible on the basis of our current knowledge of atmospheric chemistry. As a consequence of the stable relationship between OH concentrations and ultraviolet radiation that we observe, we infer that there is no long-term trend in the level of OH in the Hohenpeissenberg data set.

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Figure 1: Correlation of measured OH concentrations with simultaneously observed ozone photolysis frequencies, J (O 1 D).
Figure 2: Monthly averages of simultaneous observations of OH and J (O 1 D) measured in different years at MOHp.
Figure 3: Variance analysis of the 30-s time-resolved OH data measured at MOHp for 1999–2003.
Figure 4: Bimonthly averages of destruction and production processes of OH at MOHp.


  1. Levy, H. II Normal atmosphere: Large radical and formaldehyde concentrations predicted. Science 173, 141–143 (1971)

    Article  ADS  CAS  Google Scholar 

  2. Ehhalt, D. H. Radical ideas. Science 279, 1002–1003 doi:10.1126/science.279.5353.1002 (1998)

    Article  ADS  CAS  Google Scholar 

  3. Jacob, D. J. in Handbook of Weather, Climate and Water (eds Potter, T. D. & Colman, B. R.) 29–46 (Wiley & Sons, New York, 2003)

    Google Scholar 

  4. Lelieveld, J., Dentener, F. J., Peters, W. & Krol, M. C. On the role of hydroxyl radicals in the self-cleansing capacity of the troposphere. Atmos. Chem. Phys. 4, 2337–2344 (2004)

    Article  ADS  CAS  Google Scholar 

  5. Prinn, R. G. et al. Evidence for substantial variations of atmospheric hydroxyl radicals in the past two decades. Science 292, 1882–1888 (2001)

    Article  ADS  CAS  Google Scholar 

  6. Manning, M. R., Lowe, D. C., Moss, R. C., Bodeker, G. E. & Allan, W. Short-term variations in the oxidizing power of the atmosphere. Nature 436, 1001–1004 (2005)

    Article  ADS  CAS  Google Scholar 

  7. Perner, D. et al. Measurements of tropospheric OH concentrations: A comparison of field data with model predictions. J. Atmos. Chem. 5, 185–216 (1987)

    Article  ADS  CAS  Google Scholar 

  8. Platt, U., Rateike, M., Junkermann, W., Rudolph, J. & Ehhalt, D. H. New tropospheric OH measurements. J. Geophys. Res. 93, 5159–5166 (1988)

    Article  ADS  Google Scholar 

  9. Dorn, H.-P., Callies, J., Platt, U. & Ehhalt, D. H. Measurement of tropospheric OH concentrations by laser long-path absorption spectroscopy. Tellus B 40, 437–445 (1988)

    Article  ADS  Google Scholar 

  10. Eisele, F. L. & Tanner, D. J. Ion-assisted tropospheric OH measurements. J. Geophys. Res. 96, 9295–9308 (1991)

    Article  ADS  CAS  Google Scholar 

  11. Wennberg, P. O. et al. In situ measurements of OH and HO2 in the upper troposphere and stratosphere. J. Atmos. Sci. 52, 3413–3420 (1995)

    Article  ADS  Google Scholar 

  12. Crosley, D. R. The measurement of OH and HO2 in the atmosphere. J. Atmos. Sci. 52, 3299–3314 (1995)

    Article  ADS  Google Scholar 

  13. Brune, W. H., Stevens, P. S. & Mather, J. H. Measuring OH and HO2 in the troposphere by laser-induced fluorescence at low pressure. J. Atmos. Sci. 52, 3328–3336 (1995)

    Article  ADS  Google Scholar 

  14. Heard, D. E. & Pilling, M. J. Measurement of OH and HO2 in the troposphere. Chem. Rev. 103, 5163–5198 (2003)

    Article  CAS  Google Scholar 

  15. World Meteorological Organisation Strategy for the Implementation of the Global Atmosphere Watch Programme (2001–2007) (GAW Rep. No. 142, WMO TD No 1077, WMO, Geneva, 2001)

  16. Deutscher Wetterdienst, Global Atmosphere Watch. (2002).

  17. Holland, F., Aschmutat, U., Heßling, M., Hofzumahaus, A. & Ehhalt, D. H. Highly time resolved measurements of OH during POPCORN using laser-induced fluorescence spectroscopy. J. Atmos. Chem. 31, 205–225 (1998)

    Article  CAS  Google Scholar 

  18. Brauers, Th., Hausmann, M., Bister, A., Kraus, A. & Dorn, H.-P. OH radicals in the boundary layer of the Atlantic Ocean 1. Measurements by long-path laser absorption spectroscopy. J. Geophys. Res. 106, 7399–7414 (2001)

    Article  ADS  CAS  Google Scholar 

  19. Holland, F., Hofzumahaus, A., Schäfer, J., Kraus, A. & Pätz, H.-W. Measurements of OH and HO2 radical concentrations and photolysis frequencies during BERLIOZ. J. Geophys. Res. 108, 8246, doi:10.1029/2001JD001393 (2003)

    Article  Google Scholar 

  20. Berresheim, H., Plass-Dülmer, C., Elste, T., Mihalopoulos, N. & Rohrer, F. OH in the coastal boundary layer of Crete during MINOS: Measurements and relationship with ozone photolysis. Atmos. Chem. Phys. 3, 639–649 (2003)

    Article  ADS  CAS  Google Scholar 

  21. Ehhalt, D. H., Dorn, H.-P. & Poppe, D. The chemistry of the hydroxyl radical in the troposphere. Proc. R. Soc. Edinb. B 97, 17–34 (1991)

    Google Scholar 

  22. Ehhalt, D. H. & Rohrer, F. Dependence of the OH concentration on solar UV. J. Geophys. Res. 105, 3565–3571 (2000)

    Article  ADS  CAS  Google Scholar 

  23. Faloona, I. et al. Nighttime observations of anomalously high levels of hydroxyl radicals above a deciduous forest canopy. J. Geophys. Res. 106 (D20), 24315–24333 (2001)

    Article  ADS  CAS  Google Scholar 

  24. Hanisco, T. F. et al. Sources, sinks, and the distribution of OH in the lower stratosphere. J. Phys. Chem. 105, 1543–1553 (2001)

    Article  CAS  Google Scholar 

  25. Berresheim, H., Elste, T., Plass-Dülmer, C., Eisele, F. L. & Tanner, D. J. Chemical ionization mass spectrometer for long-term measurements of atmospheric OH and H2SO4 . Int. J. Mass Spectrom. 202, 91–109 (2000)

    Article  CAS  Google Scholar 

  26. Bohn, B., Kraus, A., Müller, M. & Hofzumahaus, A. Measurement of atmospheric O3 → O(1D) photolysis frequencies using filterradiometry. J. Geophys. Res. 109, D10S90, doi: 10.1029/2003JD004319 (2004)

    Article  ADS  Google Scholar 

  27. Stockwell, W. R., Kirchner, F., Kuhn, M. & Seefeld, S. A new mechanism for regional atmospheric chemistry modelling. J. Geophys. Res. 102, 25847–25879 (1997)

    Article  ADS  CAS  Google Scholar 

  28. Geiger, H., Barnes, I., Bejan, J., Benter, T. & Spittler, M. The tropospheric degradation of isoprene: an updated module for the regional atmospheric chemistry mechanism. Atmos. Environ. 37, 1503–1519 (2003)

    Article  ADS  CAS  Google Scholar 

  29. Sillman, S., Logan, J. A. & Wofsy, S. The sensitivity of ozone to nitrogen oxides and hydrocarbons in regional ozone episodes. J. Geophys. Res. 95, 1837–1851 (1990)

    Article  ADS  Google Scholar 

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We thank F. Eisele and D. Tanner for help in setting up the CIMS system at MOHp, T. Elste and G. Stange for OH measurements, and E. Tensing for J (O1D) measurements, D. H. Ehhalt, A. Wahner and C. Plass-Dülmer for discussions, the GAW team at MOHp for the ancillary data, and DWD/BMVBS for financial support.

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Correspondence to Franz Rohrer.

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Reprints and permissions information is available at The authors declare no competing financial interests. Requests for the Hohenpeissenberg data sets should be addressed to H.B. (

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Rohrer, F., Berresheim, H. Strong correlation between levels of tropospheric hydroxyl radicals and solar ultraviolet radiation. Nature 442, 184–187 (2006).

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