Chapter

Climate and Weather of the Sun-Earth System (CAWSES)

Part of the series Springer Atmospheric Sciences pp 247-273

The Influence of Energetic Particles on the Chemistry of the Middle Atmosphere

  • Thomas ReddmannAffiliated withKarlsruhe Institute of Technology (KIT), Inst. for Meteorology and Climate Research Email author 
  • , Bernd FunkeAffiliated withInstituto de Astrofisica de Andalucia (CSIC)
  • , Paul KonopkaAffiliated withInstitute for Energy and Climate Research – Stratosphere (IEK-7) Forschungszentrum Jülich GmbH (FZJ)
  • , Gabriele StillerAffiliated withKarlsruhe Institute of Technology (KIT), Inst. for Meteorology and Climate Research
  • , Stefan VersickAffiliated withKarlsruhe Institute of Technology (KIT), Inst. for Meteorology and Climate Research
  • , Bärbel VogelAffiliated withInstitute for Energy and Climate Research – Stratosphere (IEK-7) Forschungszentrum Jülich GmbH (FZJ)

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Abstract

Energetic particle precipitation (EPP) during solar and geomagnetic active periods causes chemical disturbances in the lower thermosphere and in the middle atmosphere. Additional HOx (H, OH, HO2) and NOx (N, NO, NO2) are produced in the middle atmosphere, and enhancements of NOx produced in these events can be transported to the winter stratosphere. These trace species take part in ozone chemistry and, by chemical-radiative coupling, the dynamical state in the middle atmosphere can be altered. There is evidence both from observations and from chemistry-climate models that the EPP induced signal in the middle atmosphere may then propagate into the troposphere. Thus particle precipitation could connect to possible climate effects. The first step in this functional chain is the impact of EPP on the chemical composition in the middle atmosphere and lower thermosphere, and the downward transport in the polar winter middle atmosphere. The general objective of this project was to assess quantitatively the chemical composition change in the middle atmosphere by combining model simulations and observations. The study relays mainly on the observations of the MIPAS instrument on the ENVISAT satellite, whose data set has been expanded in the context of this project by a newly developed retrieval of the gas H2O2, a reservoir for the members of the HOx family. Simulations have been carried out with the two chemical transport models CLaMS and KASIMA, which cover chemistry and transport effects in the stratosphere up to the mesosphere/lower thermosphere region. The impact on the global NOy budget and (the resulting) total ozone change are assessed in these studies. In addition, the ion reaction mechanism for the conversion of N2O5 to HNO3 based on positive ion chemistry was refined. The detailed comparison of model results and observation for the SPE 2003 showed that models can simulate the impact of EPP on ozone chemistry but deficiencies exist for some minor species.