Dynamics of orographic gravity waves observed in the mesosphere over the auckland islands during the deep propagating gravity wave experiment (DEEPWAVE)

Stephen D. Eckermann, Dave Broutman, Jun Ma, James D. Doyle, Pierre Dominique Pautet, Michael J. Taylor, Katrina Bossert, Bifford P. Williams, David C. Fritts, Ronald B. Smith

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

On 14 July 2014 during the Deep Propagating Gravity Wave Experiment (DEEPWAVE), aircraft remote sensing instruments detected large-amplitude gravity wave oscillations within mesospheric airglow and sodium layers at altitudes z ~ 78-83 km downstream of the Auckland Islands, located ~1000 km south of Christchurch, New Zealand. A high-altitude reanalysis and a three-dimensional Fourier gravity wave model are used to investigate the dynamics of this event. At 0700 UTC when the first observations were made, surface flow across the islands' terrain generated linear three-dimensional wave fields that propagated rapidly to z ~ 78 km, where intense breaking occurred in a narrow layer beneath a zero-wind region at z ~ 83 km. In the following hours, the altitude of weak winds descended under the influence of a large-amplitude migrating semidiurnal tide, leading to intense breaking of these wave fields in subsequent observations starting at 1000 UTC. The linear Fourier model constrained by upstream reanalysis reproduces the salient aspects of observed wave fields, including horizontal wavelengths, phase orientations, temperature and vertical displacement amplitudes, heights and locations of incipient wave breaking, and momentum fluxes. Wave breaking has huge effects on local circulations, with inferred layer-averaged westward flow accelerations of ~350 m s-1 h-1 and dynamical heating rates of ~8 K h-1, supporting recent speculation of important impacts of orographic gravity waves from subantarctic islands on the mean circulation and climate of the middle atmosphere during austral winter.

Original languageEnglish (US)
Pages (from-to)3855-3876
Number of pages22
JournalJournal of the Atmospheric Sciences
Volume73
Issue number10
DOIs
StatePublished - 2016

Keywords

  • Aircraft observations
  • Atm/ocean structure/ phenomena
  • Circulation/ dynamics
  • Geographic location/entity
  • Gravity waves
  • Middle atmosphere
  • Mountain waves
  • Observational techniques and algorithms
  • Southern ocean
  • Wave breaking

ASJC Scopus subject areas

  • Atmospheric Science

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