Energetic particle precipitation in ECHAM5/MESSy – Part 2: Solar Proton Events
1Max Planck Institute for Chemistry, 55020 Mainz, Germany
2now at Deutsches Zentrum für Luft-und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, 82234 Weßling, Germany
3Institute for Meteorology and Climate Research, Forschungszentrum Karlsruhe, Germany
4Instituto de Astrofisica de Andalucia, Granada, Spain
Abstract. The atmospheric chemistry general circulation model ECHAM5/MESSy (EMAC) has been extended by processes that parameterize particle precipitation. Several types of particle precipitation that directly affect NOy and HOx concentrations in the middle atmosphere are accounted for and discussed in a series of papers. In part 1, the EMAC parameterization for NOx produced in the upper atmosphere by low-energy electrons is presented. Here, we discuss production of NOy and HOx associated with Solar Proton Events (SPEs). A submodel that parameterizes the effects of precipitating protons, based on flux measurements by instruments on the IMP or GOES satellites, was added to the EMAC model. Production and transport of NOy and HOx, as well as effects on other chemical species and dynamics during the 2003 Halloween SPEs are presented. Comparisons with MIPAS/ENVISAT measurements of a number of species affected by the SPE are shown and discussed. There is good agreement for NO2, but a severe disagreement is found for N2O similar to other studies. We discuss the effects of an altitude dependence of the N/NO production rate on the N2O and NOy changes during the SPE. This yields a modified parameterization that shows good agreement between MIPAS and model results for NO2, N2O, O3, and HOCl. With the ability of EMAC to relax the model meteorology to observations, accurate assessment of total column ozone loss is also possible, yielding a loss of approximately 10 DU at the end of November. Discrepancies remain for HNO3, N2O5, and ClONO2, which are likely a consequence from the missing cluster ion chemistry in the EMAC model as well as known issues with the model's NOy partitioning.