Mean winds, temperatures and the 16- and 5-day planetary waves in the mesosphere and lower thermosphere over Bear Lake Observatory (42° N, 111° W)
Mean winds, temperatures and the 16- and 5-day planetary waves in the mesosphere and lower thermosphere over Bear Lake Observatory (42° N, 111° W)
复制标题
DOI：
10.5194/acp-12-1571-2012
复制
发表时间：
2011-11
影响因子：
6.3
通讯作者：
K. Day;M. Taylor;N. Mitchell
中科院分区：
文献类型：
--
作者：
K. Day;M. Taylor;N. Mitchell
抽象的。使用Aura卫星和熊湖天文台的流星雷达(42°N，111°W)分别同时测量了中间层和低热层的大气温度和风。本研究提供的数据为2008年3月至2011年7月。熊湖天文台夏季观测的平均风表明，4、8月流星高空的经向风为赤道风，月平均风速为−12 m S−1。平均风与该地区的温度密切相关，夏季中层最冷的温度与最强的赤道经向风发生在同一时间。全年大部分时间纬向风偏东，夏季存在高达~4.5m的S、−、1 km、−、1强的纬向风切变。然而，西风是在冬季的高空观察到的，有时在春分期间也会出现。在平均风速和平均气温中观察到了相当大的年际变化。将观测到的风与URAP和HWM-07进行了比较，发现了一些很大的差异。我们的雷达纬向风观测通常比URAP模式纬向风预测的更偏东。考虑到雷达经向风，与HWM-07相比，我们的观测显示夏季所有流星高度都有赤道气流，而HWM-07则表明在较低的高度只有微弱的赤道气流，甚至是极地气流。然而，雷达观测到的纬向风与HWM-07模拟的纬向风在结构和强度上大致相似。在雷达风数据和Aura温度数据中，16天和5天行星波的特征都很明显。对于16天和5天的波浪，短暂的波浪事件可以达到高达~15m的S−1和8K和20m S−1和10K的大幅度。在16天和5天的行星波振幅中观察到了明显的季节和短期变化。16天波在冬季波幅最大，夏季也存在，但波幅较小。5日波在冬季和夏末波幅最大。在四年的观测中，行星波的幅度有明显的年际变化。识别出了约41幕大振幅波的发生。对于16天和5天波，通过学生T检验的这些事件的温度和风幅AT和AW被发现分别与AT=0.34AW和AT=0.62AW相关。
Abstract. Atmospheric temperatures and winds in the mesosphere and lower thermosphere have been measured simultaneously using the Aura satellite and a meteor radar at Bear Lake Observatory (42° N, 111° W), respectively. The data presented in this study is from the interval March 2008 to July 2011. The mean winds observed in the summer-time over Bear Lake Observatory show the meridional winds to be equatorward at meteor heights during April−August and to reach monthly-mean velocities of −12 m s−1. The mean winds are closely related to temperatures in this region of the atmosphere and in the summer the coldest mesospheric temperatures occur about the same time as the strongest equatorward meridional winds. The zonal winds are eastward through most of the year and in the summer strong eastward zonal wind shears of up to ~4.5 m s−1 km−1 are present. However, westward winds are observed at the upper heights in winter and sometimes during the equinoxes. Considerable inter-annual variability is observed in the mean winds and temperatures. Comparisons of the observed winds with URAP and HWM-07 reveal some large differences. Our radar zonal wind observations are generally more eastward than predicted by the URAP model zonal winds. Considering the radar meridional winds, in comparison to HWM-07 our observations reveal equatorward flow at all meteor heights in the summer whereas HWM-07 suggests that only weakly equatorward, or even poleward flows occur at the lower heights. However, the zonal winds observed by the radar and modelled by HWM-07 are generally similar in structure and strength. Signatures of the 16- and 5-day planetary waves are clearly evident in both the radar-wind data and Aura-temperature data. Short-lived wave events can reach large amplitudes of up to ~15 m s−1 and 8 K and 20 m s−1 and 10 K for the 16- and 5-day waves, respectively. A clear seasonal and short-term variability are observed in the 16- and 5-day planetary wave amplitudes. The 16-day wave reaches largest amplitude in winter and is also present in summer, but with smaller amplitudes. The 5-day wave reaches largest amplitude in winter and in late summer. An inter-annual variability in the amplitude of the planetary waves is evident in the four years of observations. Some 41 episodes of large-amplitude wave occurrence are identified. Temperature and wind amplitudes for these episodes, AT and AW, that passed the Student T-test were found to be related by, AT = 0.34 AW and AT = 0.62 AW for the 16- and 5-day wave, respectively.