Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 16, 5853-5866, 2016
https://doi.org/10.5194/acp-16-5853-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
13 May 2016
Atmospheric changes caused by galactic cosmic rays over the period 1960–2010
Charles H. Jackman1, Daniel R. Marsh2, Douglas E. Kinnison2, Christopher J. Mertens3, and Eric L. Fleming1,4 1NASA Goddard Space Flight Center, Greenbelt, MD, USA
2National Center for Atmospheric Research, Boulder, CO, USA
3NASA Langley Research Center, Hampton, VA, USA
4Science Systems and Applications Inc., Lanham, MD, USA
Abstract. The Specified Dynamics version of the Whole Atmosphere Community Climate Model (SD-WACCM) and the Goddard Space Flight Center two-dimensional (GSFC 2-D) models are used to investigate the effect of galactic cosmic rays (GCRs) on the atmosphere over the 1960–2010 time period. The Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) computation of the GCR-caused ionization rates are used in these simulations. GCR-caused maximum NOx increases of 4–15 % are computed in the Southern polar troposphere with associated ozone increases of 1–2 %. NOx increases of  ∼ 1–6 % are calculated for the lower stratosphere with associated ozone decreases of 0.2–1 %. The primary impact of GCRs on ozone was due to their production of NOx. The impact of GCRs varies with the atmospheric chlorine loading, sulfate aerosol loading, and solar cycle variation. Because of the interference between the NOx and ClOx ozone loss cycles (e.g., the ClO + NO2+ M  →  ClONO2+ M reaction) and the change in the importance of ClOx in the ozone budget, GCRs cause larger atmospheric impacts with less chlorine loading. GCRs also cause larger atmospheric impacts with less sulfate aerosol loading and for years closer to solar minimum. GCR-caused decreases of annual average global total ozone (AAGTO) were computed to be 0.2 % or less with GCR-caused column ozone increases between 1000 and 100 hPa of 0.08 % or less and GCR-caused column ozone decreases between 100 and 1 hPa of 0.23 % or less. Although these computed ozone impacts are small, GCRs provide a natural influence on ozone and need to be quantified over long time periods. This result serves as a lower limit because of the use of the ionization model NAIRAS/HZETRN which underestimates the ion production by neglecting electromagnetic and muon branches of the cosmic ray induced cascade. This will be corrected in future works.

Citation: Jackman, C. H., Marsh, D. R., Kinnison, D. E., Mertens, C. J., and Fleming, E. L.: Atmospheric changes caused by galactic cosmic rays over the period 1960–2010, Atmos. Chem. Phys., 16, 5853-5866, https://doi.org/10.5194/acp-16-5853-2016, 2016.
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Short summary
Two global models were used to investigate the impact of galactic cosmic ray (GCRs) on the atmosphere over the 1960-2010 time period. The primary impact of the naturally occurring GCRs on ozone was found to be due to their production of NOx and this impact varies with the atmospheric chlorine loading, sulfate aerosol loading, and solar cycle variation. GCR-caused decreases of annual average global total ozone were computed to be 0.2 % or less.
Two global models were used to investigate the impact of galactic cosmic ray (GCRs) on the...
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