Dynamics of the lower thermosphere over South Pole from meteor radar wind measurements

Abstract

Hourly wind measurements were obtained nearly continuously over these time periods, at an approximate altitude of 95 km and at about 2• latitude from South Pole along the longitude meridians 0• , 90• E, 90• W, and 180• . The scientific advances achieved to date through analyses of these data are presented, including updates to several of our previously published works. The findings addressed herein include the following: (1) Strong divergences of zonal-mean meridional winds occasionally occur over South Pole, implying extreme vertical winds; (2) The monthly mean zonally asymmetric (zonal wavenumber s = 1) wind component varies during the year in a manner consistent with migration of the center of the polar vortex with respect to the geographic (rotational) pole; (3) Strong (>15 m/s) westward-propagating migrating diurnal (s = 1) and non-migrating semidiurnal (s = 1) oscillations exist except during winter months; (4) Long-period (∼2-10 days) waves exist during winter months which are primarily eastward-propagating; (5) Intradiurnal (periods ∼6-11.5 hours) westward-propagating oscillations exist, which are thought to be gravitational normal modes, or "Lamb" waves.

Mean winds and tides in the mesosphere and lower thermosphere above Halley, Antarctica

“…In agreement with the results presented here, they reported a stronger summer amplitude than winter with a greater summertime maximum in the meridional wind than the zonal wind. For example, Molodezhnaya January amplitudes of 13.7 m s À1 meridional and 10.6 m s À1 zonal compared to July amplitudes of 4.0 and 3.6 m s À1 , respectively are reported in excellent quantitative agreement with those observed at Halley, a result also observed in the meridional wind around South Pole from meteor wind data (Forbes et al, 1999) and MF radar data from McMurdo (Riggin et al, 1999). The seasonal variation in the tidal phase at 95 km at Molodezhnaya shows the same summer-to-winter transition in both the components of the wind with a wintertime phase shift of $10 h lasting for only a month in the zonal wind, but for around 4 months in the meridional.…”

A preliminary comparison of observations with MF radars in Wuhan and Yamagawa at 30–

“…Besides the stationary planetary wave, the nonmigrating tides are also proposed to explain the longitudinal dependences. Forbes et al (1999) have obtained 12 h oscillations with zonal wave number one using Meteor radar data at south pole, which suggest the nonmigrating tides could dominant the pole MLT regions. With satellite data, Oberheide and Gussev (2002) have got that the nonmigrating tides can become dominant above 90 km level in the equatorial regions.…”

A note on the semidiurnal non-migrating tide at polar latitudes

“…and intermittent in winter (Portnyagin et al, 1998, Fig. 1;Forbes et al, 1999). They surmised that this non-migrating semidiurnal component is excited in terms of nonlinear interaction of the migrating s = 2 semidiurnal tide with stationary planetary wave with s = 1, which is excited in the troposphere and propagates into the winter stratosphere.…”