Articles | Volume 17, issue 5
Atmos. Chem. Phys., 17, 3573–3604, 2017
Atmos. Chem. Phys., 17, 3573–3604, 2017
Research article
14 Mar 2017
Research article | 14 Mar 2017

HEPPA-II model–measurement intercomparison project: EPP indirect effects during the dynamically perturbed NH winter 2008–2009

Bernd Funke1, William Ball2, Stefan Bender4, Angela Gardini1, V. Lynn Harvey5, Alyn Lambert6, Manuel López-Puertas1, Daniel R. Marsh7, Katharina Meraner8, Holger Nieder4, Sanna-Mari Päivärinta3,9, Kristell Pérot10, Cora E. Randall5, Thomas Reddmann4, Eugene Rozanov2,11, Hauke Schmidt8, Annika Seppälä3, Miriam Sinnhuber4, Timofei Sukhodolov2, Gabriele P. Stiller4, Natalia D. Tsvetkova12, Pekka T. Verronen3, Stefan Versick4,14, Thomas von Clarmann4, Kaley A. Walker13, and Vladimir Yushkov12 Bernd Funke et al.
  • 1Instituto de Astrofísica de Andalucía, CSIC, Apdo. 3004, 18008 Granada, Spain
  • 2Physikalisch-Meteorologisches Observatorium, World Radiation Center, Davos, Switzerland
  • 3Earth Observation Unit, Finnish Meteorological Institute, Helsinki, Finland
  • 4Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research (IMK-ASF), P.O. Box 3640, 76021 Karlsruhe, Germany
  • 5Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, USA
  • 6Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
  • 7National Center for Atmospheric Research, Boulder, Colorado, USA
  • 8Max Planck Institute for Meteorology, Hamburg, Germany
  • 9Department of Physics, University of Helsinki, Helsinki, Finland
  • 10Chalmers University of Technology, Göteborg, Sweden
  • 11Institute for Atmospheric and Climate Science ETH, Zurich, Switzerland
  • 12Central Aerological Observatory, Moscow, Russia
  • 13Department of Physics, University of Toronto, Toronto, Ontario, Canada
  • 14Karlsruhe Institute of Technology (KIT), Steinbuch Centre for Computing (SCC), Karlsruhe, Germany

Abstract. We compare simulations from three high-top (with upper lid above 120 km) and five medium-top (with upper lid around 80 km) atmospheric models with observations of odd nitrogen (NOx  =  NO + NO2), temperature, and carbon monoxide from seven satellite instruments (ACE-FTS on SciSat, GOMOS, MIPAS, and SCIAMACHY on Envisat, MLS on Aura, SABER on TIMED, and SMR on Odin) during the Northern Hemisphere (NH) polar winter 2008/2009. The models included in the comparison are the 3-D chemistry transport model 3dCTM, the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model, FinROSE, the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA), the modelling tools for SOlar Climate Ozone Links studies (SOCOL and CAO-SOCOL), and the Whole Atmosphere Community Climate Model (WACCM4). The comparison focuses on the energetic particle precipitation (EPP) indirect effect, that is, the polar winter descent of NOx largely produced by EPP in the mesosphere and lower thermosphere. A particular emphasis is given to the impact of the sudden stratospheric warming (SSW) in January 2009 and the subsequent elevated stratopause (ES) event associated with enhanced descent of mesospheric air. The chemistry climate model simulations have been nudged toward reanalysis data in the troposphere and stratosphere while being unconstrained above. An odd nitrogen upper boundary condition obtained from MIPAS observations has further been applied to medium-top models. Most models provide a good representation of the mesospheric tracer descent in general, and the EPP indirect effect in particular, during the unperturbed (pre-SSW) period of the NH winter 2008/2009. The observed NOx descent into the lower mesosphere and stratosphere is generally reproduced within 20 %. Larger discrepancies of a few model simulations could be traced back either to the impact of the models' gravity wave drag scheme on the polar wintertime meridional circulation or to a combination of prescribed NOx mixing ratio at the uppermost model layer and low vertical resolution. In March–April, after the ES event, however, modelled mesospheric and stratospheric NOx distributions deviate significantly from the observations. The too-fast and early downward propagation of the NOx tongue, encountered in most simulations, coincides with a temperature high bias in the lower mesosphere (0.2–0.05 hPa), likely caused by an overestimation of descent velocities. In contrast, upper-mesospheric temperatures (at 0.05–0.001 hPa) are generally underestimated by the high-top models after the onset of the ES event, being indicative for too-slow descent and hence too-low NOx fluxes. As a consequence, the magnitude of the simulated NOx tongue is generally underestimated by these models. Descending NOx amounts simulated with medium-top models are on average closer to the observations but show a large spread of up to several hundred percent. This is primarily attributed to the different vertical model domains in which the NOx upper boundary condition is applied. In general, the intercomparison demonstrates the ability of state-of-the-art atmospheric models to reproduce the EPP indirect effect in dynamically and geomagnetically quiescent NH winter conditions. The encountered differences between observed and simulated NOx, CO, and temperature distributions during the perturbed phase of the 2009 NH winter, however, emphasize the need for model improvements in the dynamical representation of elevated stratopause events in order to allow for a better description of the EPP indirect effect under these particular conditions.

Short summary
Simulations from eight atmospheric models have been compared to tracer and temperature observations from seven satellite instruments in order to evaluate the energetic particle indirect effect (EPP IE) during the perturbed northern hemispheric (NH) winter 2008/2009. Models are capable to reproduce the EPP IE in dynamically and geomagnetically quiescent NH winter conditions. The results emphasize the need for model improvements in the dynamical representation of elevated stratopause events.
Final-revised paper