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Horizontal propagation of large‐amplitude mountain waves into the polar night jet
Author(s) -
Ehard Benedikt,
Kaifler Bernd,
Dörnbrack Andreas,
Preusse Peter,
Eckermann Stephen D.,
Bramberger Martina,
Gisinger Sonja,
Kaifler Natalie,
Liley Ben,
Wagner Johannes,
Rapp Markus
Publication year - 2017
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2016jd025621
Subject(s) - gravity wave , geology , polar night , stratosphere , jet stream , jet (fluid) , gravitational wave , amplitude , infragravity wave , lidar , atmosphere (unit) , geophysics , atmospheric wave , stratopause , atmospheric sciences , mesosphere , wave propagation , meteorology , longitudinal wave , physics , mechanical wave , remote sensing , mechanics , quantum mechanics , astrophysics
We analyze a large‐amplitude mountain wave event, which was observed by a ground‐based lidar above New Zealand between 31 July and 1 August 2014. Besides the lidar observations, European Centre for Medium‐Range Weather Forecasts (ECMWF) data, satellite observations, and ray tracing simulations are utilized in this study. It is found that the propagation of mountain waves into the middle atmosphere is influenced by two different processes at different stages of the event. At the beginning of the event, instabilities in a weak wind layer cause wave breaking in the lower stratosphere. During the course of the event the mountain waves propagate to higher altitudes and are refracted southward toward the polar night jet due to the strong meridional shear of the zonal wind. As the waves propagate out of the observational volume, the ground‐based lidar observes no mountain waves in the mesosphere. Ray tracing simulations indicate that the mountain waves propagated to mesospheric altitudes south of New Zealand where the polar night jet advected the waves eastward. These results underline the importance of considering horizontal propagation of gravity waves, e.g., when analyzing locally confined observations of gravity waves.