Long-term observations of the wind field in the Antarctic and Arctic mesosphere and lower-thermosphere at conjugate latitudes

Abstract

[1] Mean winds, semidiurnal and diurnal tides, and trends and long-period oscillations spanning a solar cycle (from early 1999 through June 2010) measured by medium frequency (MF) radars at conjugate Antarctic and Arctic latitudes (Syowa, Antarctica, 69°S, 39.6°E, and Andenes, Norway, 69.3°N, 16°E) are described and compared. Zonal mean winds are stronger and more uniform from year to year over the Antarctic, with a stronger eastward winter jet spanning the range of altitudes presented (70 to 96 km). The summer westward jet is also stronger and maximizes at higher altitudes over the Antarctic than over the Arctic. The eastward winter jet over the Arctic, while generally weaker, exhibits a localized maximum in late winter at ∼2 to 3 year intervals. Meridional mean winds likewise achieve somewhat stronger maxima at higher altitudes over the Antarctic than over the Arctic. Semidiurnal tide amplitudes are typically somewhat larger over the Antarctic and similar in the two components, with maxima at ∼85 km or above and narrow responses that tend to cluster from ∼February to May and ∼September to November over the Antarctic and from ∼December to February and ∼June to September over the Arctic. Zonal diurnal tide amplitudes are quite similar between the sites, with maxima extending from ∼70 to 90 km and slightly stronger over the Antarctic. Meridional diurnal amplitudes display more significant growth with altitude, achieve stronger maxima at the highest altitudes presented, and typically exhibit a single and narrow maximum during December to February over the Antarctic and double maxima from ∼May to September over the Arctic. Also discussed are trends and long-period oscillations over a solar cycle observed in these mean and tidal wind fields.

Climatology of semidiurnal lunar and solar tides at middle and high latitudes: Interhemispheric comparison

“…In principle, given the mean zonal and meridional winds similarities described in the last paragraph and in previous studies [e.g., Iimura et al ., ; Fritts et al ., ], one would expect comparable characteristics between different hemisphere's tidal components. The analysis carried out in this study tells us that they are different though.…”

A conjugate study of mean winds and planetary waves employing enhanced meteor radars at Rio Grande, Argentina (53.8°S) and Juliusruh, Germany (54.6°N)

“…Ground‐based studies of the mesosphere and lower thermosphere (MLT) have addressed interhemispheric differences in mean temperatures and winds, tides, planetary waves (PWs), gravity waves (GWs), and the constituent distributions and microphysical processes that depend on them from midlatitudes to polar latitudes [e.g., Vincent et al , 1988; Avery et al , 1989; Portnyagin et al , 1993a, 1993b, 2006; Fraser et al , 1995; Huaman and Balsley , 1999; Dowdy et al , 2001, 2007; Chu et al , 2003; Kishore et al , 2003; Riggin et al , 2003; Day and Mitchell , 2010a, 2010b; Iimura et al , 2011]. Similar studies employing satellite data have provided a more uniform global perspective for specific fields.…”

Seasonal and Interannual Variation of Mesospheric Gravity Waves Based on MF Radar Observations over 15 Years at Syowa Station in the Antarctic

“…The MF radar has continuously operated at Syowa Station (69.0°S, 39.6°E) since March 1999, and it has provided horizontal wind at altitudes of 50−120 km in the mesosphere and lower thermosphere for approximately 17 years. Iimura et al (2011) reported seasonal variations and trends in the TWs observed at Syowa Station. Murphy et al (2007) examined the climatology of the PWs at Davis Station (68.3°S, 77.6°E) for three wave period ranges and discussed their differences.…”