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Observations of gravity wave refraction and its causes and consequences
  • +8
  • Markus Geldenhuys,
  • Bernd Kaifler,
  • Peter Preusse,
  • Joern Ungermann,
  • Peter Alexander,
  • Lukas Krasauskas,
  • Sebastian Rhode,
  • Wolfgang Woiwode,
  • Manfred Ern,
  • Markus Rapp,
  • Martin Riese
Markus Geldenhuys
Forschungszentrum Jülich, Institute of Energy- and Climate Research, Stratosphere (IEK-7), Jülich, Germany

Corresponding Author:[email protected]

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Bernd Kaifler
Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
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Peter Preusse
Forschungszentrum Jülich, Institute of Energy- and Climate Research, Stratosphere (IEK-7), Jülich, Germany
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Joern Ungermann
Forschungszentrum Jülich, Institute of Energy- and Climate Research, Stratosphere (IEK-7), Jülich, Germany
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Peter Alexander
Instituto de Fı́sica de Buenos Aires, CONICET, Buenos Aires, Argentina
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Lukas Krasauskas
Forschungszentrum Jülich, Institute of Energy- and Climate Research, Stratosphere (IEK-7), Jülich, Germany
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Sebastian Rhode
Forschungszentrum Jülich, Institute of Energy- and Climate Research, Stratosphere (IEK-7), Jülich, Germany
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Wolfgang Woiwode
Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe, Germany
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Manfred Ern
Forschungszentrum Jülich, Institute of Energy- and Climate Research, Stratosphere (IEK-7), Jülich, Germany
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Markus Rapp
Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
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Martin Riese
Forschungszentrum Jülich, Institute of Energy- and Climate Research, Stratosphere (IEK-7), Jülich, Germany
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Abstract

Horizontal gravity wave (GW) refraction was observed around the Andes and Drake Pas- sage during the SouthTRAC campaign. GWs interact with the background wind through refraction and dissipation. This interaction helps to drive mid-atmospheric circulations and slows down the polar vortex by taking GW momentum flux from one location to an- other. The SouthTRAC campaign was composed to gain improved understanding of the propagation and dissipation of GWs. This study uses observational data from this cam- paign collected by the German research aircraft on 12 September 2019. During the cam- paign a minor sudden stratospheric warming in the Southern Hemisphere occurred, which heavily influenced GW propagation and refraction and thus also the location and amount of GW momentum flux deposition. Observations include, amongst others, measurements from below the aircraft by GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere), and above the aircraft by ALIMA (Airborne Lidar for the Middle Atmosphere). Refraction is identified in two different GW packets as low as ≈4 km and as high as 58 km. One GW packet of orographic origin and one of non-orographic ori- gin is used to investigate refraction. Observations are supplemented by the Gravity-wave Regional Or Global Ray Tracer (GROGRAT), a simplified mountain wave model, ERA5 data and high-resolution (3 km) WRF data. Contrary to some previous studies we find that refraction makes a noteworthy contribution in the amount and the location of GW momentum flux deposition. This case study highlights the importance of refraction and provides compelling arguments that models should account for this.