Articles | Volume 17, issue 24
Atmos. Chem. Phys., 17, 14937–14953, 2017

Special issue: Sources, propagation, dissipation and impact of gravity waves...

Special issue: The Polar Stratosphere in a Changing Climate (POLSTRACC) (ACP/AMT...

Atmos. Chem. Phys., 17, 14937–14953, 2017

Research article 18 Dec 2017

Research article | 18 Dec 2017

First tomographic observations of gravity waves by the infrared limb imager GLORIA

Isabell Krisch1, Peter Preusse1, Jörn Ungermann1, Andreas Dörnbrack2, Stephen D. Eckermann3, Manfred Ern1, Felix Friedl-Vallon4, Martin Kaufmann1, Hermann Oelhaf4, Markus Rapp2,5, Cornelia Strube1, and Martin Riese1,6 Isabell Krisch et al.
  • 1Forschungszentrum Jülich, Institute of Energy- and Climate Research, Stratosphere (IEK-7), Jülich, Germany
  • 2Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
  • 3E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DC, USA
  • 4Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe, Germany
  • 5Meteorologisches Institut München, Ludwig-Maximilians-Universität München, Munich, Germany
  • 6Institut für Atmosphären- und Umweltforschung, Bergische Universität Wuppertal, Wuppertal, Germany

Abstract. Atmospheric gravity waves are a major cause of uncertainty in atmosphere general circulation models. This uncertainty affects regional climate projections and seasonal weather predictions. Improving the representation of gravity waves in general circulation models is therefore of primary interest. In this regard, measurements providing an accurate 3-D characterization of gravity waves are needed. Using the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA), the first airborne implementation of a novel infrared limb imaging technique, a gravity wave event over Iceland was observed. An air volume disturbed by this gravity wave was investigated from different angles by encircling the volume with a closed flight pattern. Using a tomographic retrieval approach, the measurements of this air mass at different angles allowed for a 3-D reconstruction of the temperature and trace gas structure. The temperature measurements were used to derive gravity wave amplitudes, 3-D wave vectors, and direction-resolved momentum fluxes. These parameters facilitated the backtracing of the waves to their sources on the southern coast of Iceland. Two wave packets are distinguished, one stemming from the main mountain ridge in the south of Iceland and the other from the smaller mountains in the north. The total area-integrated fluxes of these two wave packets are determined. Forward ray tracing reveals that the waves propagate laterally more than 2000 km away from their source region. A comparison of a 3-D ray-tracing version to solely column-based propagation showed that lateral propagation can help the waves to avoid critical layers and propagate to higher altitudes. Thus, the implementation of oblique gravity wave propagation into general circulation models may improve their predictive skills.

Short summary
Using the infrared limb imager GLORIA, the 3-D structure of mesoscale gravity waves in the lower stratosphere was measured for the first time, allowing for a complete 3-D characterization of the waves. This enables the precise determination of the sources of the waves in the mountain regions of Iceland with backward ray tracing. Forward ray tracing shows oblique propagation, an effect generally neglected in global atmospheric models.
Final-revised paper