A study of the dynamical characteristics of inertia–gravity waves in the Antarctic mesosphere combining the PANSY radar and a non-hydrostatic general circulation model
<p>This study aims to examine the dynamical characteristics of gravity waves with relatively low frequency in the Antarctic mesosphere via the first long-term simulation using a high-top high-resolution non-hydrostatic general circulation model (NICAM). Successive runs lasting 7 days are perfo...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/3395/2019/acp-19-3395-2019.pdf |
| Summary: | <p>This study aims to examine the dynamical characteristics of gravity waves
with relatively low frequency in the Antarctic mesosphere via the first
long-term simulation using a high-top high-resolution non-hydrostatic general
circulation model (NICAM). Successive runs lasting 7 days are performed using
initial conditions from the MERRA reanalysis data with an overlap of 2 days
between consecutive runs in the period from April to August in 2016. The data
for the analyses were compiled from the last 5 days of each run. The
simulated wind fields were closely compared to the MERRA reanalysis data and
to the observational data collected by a complete PANSY (Program of the
Antarctic Syowa MST/IS radar) radar system installed at Syowa Station
(39.6<span class="inline-formula"><sup>∘</sup></span> E, 69.0<span class="inline-formula"><sup>∘</sup></span> S). It is shown that the NICAM mesospheric
wind fields are realistic, even though the amplitudes of the wind
disturbances appear to be larger than those from the radar observations.</p>
<p>The power spectrum of the meridional wind fluctuations at a height of 70 km
has an isolated and broad peak at frequencies slightly lower than the
inertial frequency, <span class="inline-formula"><i>f</i></span>, for latitudes from 30 to 75<span class="inline-formula"><sup>∘</sup></span> S, while another isolated peak is observed at frequencies of approximately
2<span class="inline-formula"><i>π</i>∕8</span> h at latitudes from 78 to 90<span class="inline-formula"><sup>∘</sup></span> S. The
spectrum of the vertical fluxes of the zonal momentum also has an isolated
peak at frequencies slightly lower than <span class="inline-formula"><i>f</i></span> at latitudes from 30 to 75<span class="inline-formula"><sup>∘</sup></span> S at a height of 70 km. It is shown that these isolated
peaks are primarily composed of gravity waves with horizontal wavelengths of
more than 1000 km. The latitude–height structure of the momentum fluxes
indicates that the isolated peaks at frequencies slightly lower than <span class="inline-formula"><i>f</i></span>
originate from two branches of gravity wave propagation paths. It is thought
that one branch originates from 75<span class="inline-formula"><sup>∘</sup></span> S due to topographic gravity
waves generated over the Antarctic Peninsula and its coast, while more than
80 % of the other branch originates from 45<span class="inline-formula"><sup>∘</sup></span> S and includes
contributions by non-orographic gravity waves. The existence of isolated
peaks in the high-latitude region in the mesosphere is likely explained by
the poleward propagation of quasi-inertia–gravity waves and by the
accumulation of wave energies near the inertial frequency at each latitude.</p> |
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| ISSN: | 1680-7316 1680-7324 |