EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Middle-Atmosphere Mountain Waves and Drag Near the Drake Passage: Observations, mini-MIP, and an OSSE

Christopher Kruse1, Joan Alexander2, Lars Hoffmann3, Inna Polichtchouk4, Annelize van Niekerk5, Riwal Plougonven6, Corwin Wrioght7, Julio Bacmeister8, Manfred Ern3, Kaoru Sato9, Ryosuke Shibuya10, Catrin Meyer3, Olaf Stein3, Laura Holt2, Petr Šácha11, and Sonja Gisinger12
Christopher Kruse et al.
  • 1Advanced Study Program, National Center for Atmospheric Research, Boulder, United States of America (
  • 2Northwest Research Associates, Boulder, United States of America (
  • 3Forschungszentrum Jülich GmbH, Jülich, Germany (
  • 4Earth System Modeling Section, ECMWF, Reading, United Kingdom (
  • 5Met Office, Exeter, United Kingdom (
  • 6Laboratoire de Meteorologie Dynamique, Ecole Polytechnique, Palaiseau, France (
  • 7Centre for Space, Atmospheric and Oceanic Science, University of Bath, Bath, United Kingdom (
  • 8Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, United States of America (
  • 9Department of Earth and Planetary Science, University of Tokyo, Tokyo, Japan (
  • 10Atmosphere and Ocean Research Institute, University of Tokyo, Tokyo, Japan (
  • 11Department of Applied Physics Earth Sciences, University of Vigo, Ourense, Spain (
  • 12Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft und Raumfahrt, Oberpfaffenhofen, Germany (

Orographic gravity wave (OGW) drag is one of the fundamental physics parametrizations employed in every global numerical model across timescales from weather to climate. These parameterizations have significant influences, both direct and indirect, on the atmosphere’s general circulation from the troposphere at least through the mesosphere. Despite their significant influence, observational constraints on these parameterizations are still largely lacking.

Presented here is a team project jointly supported by SPARC and the International Space Science Institute with the overall objective of providing new quantitative constraints for OGW drag parameterizations. Specific objectives are to evaluate methods that quantify vertical fluxes of horizontal momentum (MF) from satellite observations via an observing system simulation experiment (OSSE), a validation of WRF, UKMO, ECMWF, and ICON models against satellite and balloon observations, and an inter-comparison of OGW properties (e.g. MF and drag) within these models. Evaluation of satellite-based estimates of MF and model validation/inter-comparison will help to better quantify actual MF in the stratosphere, providing the best stratospheric MF and drag estimates for parameterizations to reproduce to date.

Two unique aspects of the project are that all models involved are deep, extending up to 1 Pa. The motivations for doing so was to include entire instrument weighting functions for AIRS observations, allowing direct, quantitative comparison between AIRS (and other satellite-borne) observations and the models. The second is the effort to perform an OSSE within the simulations, allowing comparison between MF from satellite-based methods within the models to the true MF in the models.

Preliminary results show that higher-res models (dx = 3 km) compare well and produce significantly more MF than lower-res global models, but the higher-res models still underrepresent OGW amplitudes. Mesospheric tides in analyses used to force the models significantly modulate resolved GWs and their drags.

How to cite: Kruse, C., Alexander, J., Hoffmann, L., Polichtchouk, I., van Niekerk, A., Plougonven, R., Wrioght, C., Bacmeister, J., Ern, M., Sato, K., Shibuya, R., Meyer, C., Stein, O., Holt, L., Šácha, P., and Gisinger, S.: Middle-Atmosphere Mountain Waves and Drag Near the Drake Passage: Observations, mini-MIP, and an OSSE, EGU General Assembly 2020, Online, 4–8 May 2020,, 2020

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Presentation version 1 – uploaded on 08 May 2020
  • CC1: Comment on EGU2020-6118, Paul Pukite, 15 May 2020

    Regarding the Drake Passage, Woodworth and Hibbert were able to extract the long-period tidal forcing from bottom-pressure readings. These long-period tides can then be used to calibrate the forcings used to drive ENSO and other climate dipole cycles.

    This chart shows thecomposite  tidal cycle used in the model compared against the Drake Passage.


    Since tidals are global and show only amplitude and phase differences between locations, this forcing can be used to drive the ENSO behavior via the nonlinear LTE solution


    See this blog post for other citations and charts: