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. This study aims to examine the dynamical characteristics of gravity waveswith relatively low frequency in the Antarctic mesosphere via the firstlong-term simulation using a high-top high-resolution non-hydrostatic generalcirculation model (NICAM). Successive runs lasting 7 days are performed usinginitial conditions from the MERRA reanalysis data with an overlap of 2 daysbetween consecutive runs in the period from April to August in 2016. The datafor the analyses were compiled from the last 5 days of each run. Thesimulated wind fields were closely compared to the MERRA reanalysis data andto the observational data collected by a complete PANSY (Program of theAntarctic Syowa MST/IS radar) radar system installed at Syowa Station(39.6 ∘  E, 69.0 ∘  S). It is shown that the NICAM mesosphericwind fields are realistic, even though the amplitudes of the winddisturbances appear to be larger than those from the radar observations. The power spectrum of the meridional wind fluctuations at a height of 70 kmhas an isolated and broad peak at frequencies slightly lower than theinertial frequency, f , for latitudes from 30 to 75 ∘  S, while another isolated peak is observed at frequencies of approximately2 π∕8  h at latitudes from 78 to 90 ∘  S. Thespectrum of the vertical fluxes of the zonal momentum also has an isolatedpeak at frequencies slightly lower than f at latitudes from 30 to 75 ∘  S at a height of 70 km. It is shown that these isolatedpeaks are primarily composed of gravity waves with horizontal wavelengths ofmore than 1000 km. The latitude–height structure of the momentum fluxesindicates that the isolated peaks at frequencies slightly lower than f originate from two branches of gravity wave propagation paths. It is thoughtthat one branch originates from 75 ∘  S due to topographic gravitywaves generated over the Antarctic Peninsula and its coast, while more than80 % of the other branch originates from 45 ∘  S and includescontributions by non-orographic gravity waves. The existence of isolatedpeaks in the high-latitude region in the mesosphere is likely explained bythe poleward propagation of quasi-inertia–gravity waves and by theaccumulation of wave energies near the inertial frequency at each latitude.

atmospheric chemistry and physics

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