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

• Published in: Atmospheric chemistry and physics 2017-03, Vol.17 (5), p.3573-3604
• Main Authors: Funke, Bernd, Ball, William, Bender, Stefan, Gardini, Angela, Harvey, V. Lynn, Lambert, Alyn, López-Puertas, Manuel, Marsh, Daniel R, Meraner, Katharina, Nieder, Holger, Päivärinta, Sanna-Mari, Pérot, Kristell, Randall, Cora E, Reddmann, Thomas, Rozanov, Eugene, Schmidt, Hauke, Seppälä, Annika, Sinnhuber, Miriam, Sukhodolov, Timofei, Stiller, Gabriele P, Tsvetkova, Natalia D, Verronen, Pekka T, Versick, Stefan, von Clarmann, Thomas, Walker, Kaley A, Yushkov, Vladimir
• Format: Article
• Language: English
• Subjects: Analysis; Atmosphere; Atmospheric chemistry; Atmospheric models; Boundary conditions; Carbon monoxide; Chemistry; Climate; Climate models; Computer simulation; Descent; Energetic particles; Fluxes; Fourier transforms; Geomagnetism; Gravitational waves; Gravity wave drag; Gravity waves; Instruments; Intercomparison; Ionosphere; Lower thermosphere; Measurement; Meridional circulation; Mesosphere; Mesospheric temperatures; Middle atmosphere; Mixing ratio; Nitrogen; Nitrogen compounds; Nitrogen dioxide; Northern Hemisphere; Oxides; Ozone; Particle precipitation; Physics; Polar winter; Precipitation; Remote sensing; Representations; Satellite instruments; Satellite-borne instruments; Simulation; Stratopause; Stratosphere; Stratospheric warming; Temperature; Thermosphere; Three dimensional models; Tongue; Tracers; Troposphere; Wave drag; Winter; Winter circulation
• ISSN: 1680-7324; 1680-7316; 1680-7324
• DOI: 10.5194/acp-17-3573-2017

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,