TY - JOUR
T1 - Dynamics of orographic gravity waves observed in the mesosphere over the auckland islands during the deep propagating gravity wave experiment (DEEPWAVE)
AU - Eckermann, Stephen D.
AU - Broutman, Dave
AU - Ma, Jun
AU - Doyle, James D.
AU - Pautet, Pierre Dominique
AU - Taylor, Michael J.
AU - Bossert, Katrina
AU - Williams, Bifford P.
AU - Fritts, David C.
AU - Smith, Ronald B.
N1 - Publisher Copyright:
© 2016 American Meteorological Society.
PY - 2016
Y1 - 2016
N2 - 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.
AB - 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.
KW - Aircraft observations
KW - Atm/ocean structure/ phenomena
KW - Circulation/ dynamics
KW - Geographic location/entity
KW - Gravity waves
KW - Middle atmosphere
KW - Mountain waves
KW - Observational techniques and algorithms
KW - Southern ocean
KW - Wave breaking
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U2 - 10.1175/JAS-D-16-0059.1
DO - 10.1175/JAS-D-16-0059.1
M3 - Article
AN - SCOPUS:84994158702
SN - 0022-4928
VL - 73
SP - 3855
EP - 3876
JO - Journal of the Atmospheric Sciences
JF - Journal of the Atmospheric Sciences
IS - 10
ER -