利用HRDI／UARS资料分析东亚区域中层大气纬向风气候特征

Analysis of Climatic Features of the Zonal Winds in the Middle Atmosphere Over East Asia by Using HRDI/UARS Data Set

利用美国高层大气研究卫星(UARS)搭载的高分辨率多普勒测风仪(HRDI)获得的中层大气风场观测资料,对东亚区域中层大气纬向风的垂直分布与变化特征进行了分析研究．多年平均结果显示东亚区域中层大气纬向风具有显著的区域特征,与当前普遍使用的参考大气CIRA-86相比存在显著的不同．在冬季, 东亚区域中间层西风急流中心位于25°-35°N之间的75km高度,与CIRA-86相比,该中心纬度偏南5°, 高度偏高10 km;在秋季,东亚区域低热层高度存在一个显著的从赤道到高纬度的东风带,而CIRA-86不存在．分析结果还表明,除了夏季中纬度地区,在东亚区域上空中高层大气各高度上均存在相当显著的区域尺度扰动结构．在热带,低热层高度纬向风无论冬夏,沿纬圈方向都表现出相当显著的不均匀性,夏季这种不均匀性进一步向下扩展到55 km高度．与上述热带扰动特征相比,中纬度地区夏季的纬向风在各个高度沿纬圈相当均匀,但是在冬季,中间层和低热层高度都存在沿纬圈方向显著的纬向风扰动结构．

In this paper, the long term mean characteristics of the zonal winds in the middle atmosphere over East Asia were studied by using the HRDI/UARS measurements. The results of 7-years averaged data analysis showed that the middle atmospheric zonal winds exhibit significant regional features when compared with the CIRA-86 counterpart that has been widely used. In the region, the winter mesospheric westerly jet lies at 75 km altitude and in between 25°-35°N, which is 10 km higher and 5° farther south in latitude that of the CIRA-86. While not shown in CIRA-86, there is a clear easterly band extending from the equator to high latitudes at the altitude of lower thermosphere in autumn. Further investigation revealed the presence of considerable regional scale disturbances in the whole of the middle to upper atmosphere over East Asia, except the situations in mid-latitudes in summer. In winter, the tropical lower thermospheric zonal winds fluctuate significantly in zonal direction, and this kind of the zonal disturbances extend downward to 55 km altitude （the lower limit of the observation mode of the satellite instrument） in summer. With respect to the situation in mid-latitudes, very few zonal fluctuation can seen in the zonal winds from 55 km to 115 km altitude range in the summer season, however, the winter mesospheric and lower thermospheric zonal winds are disturbed prominently in the zonal.