Energetic particle precipitation in ECHAM5/MESSy1 – Part 1: Downward transport of upper atmospheric NO_x produced by low energy electrons (original) (raw)

2009, Atmospheric Chemistry and Physics

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 NO y and HO x concentrations in the middle atmosphere are accounted for and discussed in a series of papers. In part 1, the EMAC parameterization for NO x produced in the upper atmosphere by low-energy electrons is presented. Here, we discuss production of NO y and HO x 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 NO y and HO x , 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 NO 2 , but a severe disagreement is found for N 2 O similar to other studies. We discuss the effects of an altitude dependence of the N/NO production rate on the N 2 O and NO y changes during the SPE. This yields a modified parameterization that shows mostly good agreement between MIPAS and model results for NO 2 , N 2 O, O 3 , 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 HNO 3 , N 2 O 5 , and ClONO 2 , which are likely a consequence from Correspondence to: A. J. G. Baumgaertner (work@andreas-baumgaertner.net) the missing cluster ion chemistry and ion-ion recombination in the EMAC model as well as known issues with the model's NO y partitioning. Published by Copernicus Publications on behalf of the European Geosciences Union. 7286 A. J. G. Baumgaertner et al.: EPP in EMAC, Solar Proton Events 2003 and has been termed Halloween events and received considerable attention. Jackman et al. ( investigated both short-term and long-term effects of the Halloween SPEs. 2-D model simulations were compared to NOAA16 SBUV/2 ozone and UARS HALOE NO x measurements. In the lower and upper mesosphere, short-term ozone depletion up to 50% and greater than 70%, respectively, were found in the model results. Measurements showed a loss of approximately 40% in the lower mesosphere. Northern Hemisphere polar total ozone reduction greater than 0.5% was predicted to last for 8 months. SCIAMACHY/ENVISAT measurements of the ozone depletion were shown by Rohen et al. (2005) and Rohen et al. (2006). In addition, Rohen et al. (2005) compared the ozone depletion with results from a 2-D chemistry transport model based on SLIMCAT. In the five weeks following the SPEs the ozone depletion was captured fairly well by the model and agrees approximately with the model results of Jackman et al. (2005). The MIPAS instrument on board ENVISAT has been used extensively to study effects of the Halloween SPE on the chemical composition of the middle atmosphere. For example, effects on NO x and ozone are shown in López-Puertas et al. (2005a), von Clarmann et al. (2005) shows HOCl and ClO perturbations, HNO 3 , N 2 O 5 , and ClONO 2 changes are discussed in López-Puertas et al. (2005b), and N 2 O enhancements are discussed by Funke et al. (2008). Jackman et al. (2008) noted that MIPAS measurements of the HNO 3 enhancements were unexpectedly large; Verronen et al. (2008) attributed them to ion-ion recombination between NO − 3 and H + . Jackman et al. (2007) discussed dynamical effects in the mesosphere using results from the TIME-GCM model. SPEinduced cooling up to 2.6 K in the lower mesosphere and heating up to 2 K at 90 km were found. Background wind velocities changed up to 25%.