Articles | Volume 17, issue 6
Atmos. Chem. Phys., 17, 4031–4052, 2017
Atmos. Chem. Phys., 17, 4031–4052, 2017

Research article 24 Mar 2017

Research article | 24 Mar 2017

Observed versus simulated mountain waves over Scandinavia – improvement of vertical winds, energy and momentum fluxes by enhanced model resolution?

Johannes Wagner1, Andreas Dörnbrack1, Markus Rapp1, Sonja Gisinger1, Benedikt Ehard1, Martina Bramberger1, Benjamin Witschas1, Fernando Chouza1, Stephan Rahm1, Christian Mallaun2, Gerd Baumgarten3, and Peter Hoor4 Johannes Wagner et al.
  • 1Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt, 82234 Oberpfaffenhofen, Germany
  • 2Flugexperimente, Deutsches Zentrum für Luft- und Raumfahrt, 82234 Oberpfaffenhofen, Germany
  • 3Leibniz Institut für Atmosphären Physik, 18225 Kühlungsborn, Germany
  • 4Institut für Physik der Atmosphäre, Johannes Gutenberg Universität, 55099 Mainz, Germany

Abstract. Two mountain wave events, which occurred over northern Scandinavia in December 2013 are analysed by means of airborne observations and global and mesoscale numerical simulations with horizontal mesh sizes of 16, 7.2, 2.4 and 0.8 km. During both events westerly cross-mountain flow induced upward-propagating mountain waves with different wave characteristics due to differing atmospheric background conditions. While wave breaking occurred at altitudes between 25 and 30 km during the first event due to weak stratospheric winds, waves propagated to altitudes above 30 km and interfacial waves formed in the troposphere at a stratospheric intrusion layer during the second event. Global and mesoscale simulations with 16 and 7.2 km grid sizes were not able to simulate the amplitudes and wavelengths of the mountain waves correctly due to unresolved mountain peaks. In simulations with 2.4 and 0.8 km horizontal resolution, mountain waves with horizontal wavelengths larger than 15 km were resolved, but exhibited too small amplitudes and too high energy and momentum fluxes. Simulated fluxes could be reduced by either increasing the vertical model grid resolution or by enhancing turbulent diffusion in the model, which is comparable to an improved representation of small-scale nonlinear wave effects.

Final-revised paper