东经120°E中间层和低热层大气潮汐及其季节变化特征

Seasonal variations of the MLT tides in 120°E meridian

利用为期一年的卫星遥感温度(SABER/TIMED)资料重建了120°E子午圈内中间层和低热层大气潮汐各主要频率分量(周日、半日和8小时潮汐).这些主要频率分量随高度振幅增大,在97km高度达到显著的振幅;其中迁移性周日潮汐在97km高度出现极大振幅,然后随高度衰减.本文从考察迁移性成分和非迁移性成分各自在总潮汐中贡献角度出发,着重讨论了那些对形成该子午圈中97km高度上整体潮汐扰动起控制作用的潮汐成分.结果显示,对周日和半日频率这两种潮汐而言,迁移性成分控制了它们的总体时空分布.在春分季节,迁移性周日潮的控制作用最显著,决定了赤道和两半球热带的活动中心;其中北半球副热带地区的季节变化形势与以往利用武汉(30°N,114°E)流星雷达风测量资料开展分析得到的结果是一致的;其他季节受非迁移性成分明显影响,例如,在本文关注的2005年中,夏至季节受(1,0)模、(1,-3)模和(1,-2)模的共同影响形成了从赤道向南延伸的活动中心,极值中心位于赤道附近,振幅达到了20K以上,是全年的最大值.受迁移性成分控制,半日潮活动主要出现在两半球热带地区,北半球活动中心位于秋分季节(振幅达到13K),南半球活动中心位于春分和夏至之间.其他季节受非迁移成分的影响,形成若干分布在两半球的活动中心.在本文关注的40°S^40°N范围内,与周日潮和半日潮相比,8小时潮汐具有显著较低的振幅;另外,虽然迁移性成分在一年中的大部分时间系统地分布在两半球热带地区,但是非迁移成分具有与迁移性成分相当或更大的振幅,在整体上控制了这种潮汐的时空分布.

The authors report in the article the seasonal variations of major atmospheric tides and lower thermosphere region in the meridian at 120°E measurements covering Nov. 2004 to Jan. 2006 were used to mesosphere One-year long SABER/TIMED temperature extract the tidal components with Fourier-Least squares fit and FFT analysis, and to reconstruct the diurnal, semidiurnal and terdiurnal tides in the meridian. The migrating diurnal tides increase with altitude and attain maxima at 97 km height, then decrease sharply with altitude. The tides of other frequency increase with altitude and attain significant amplitude at 97 km height. Considering the behavior of vertical variation, the authors place their focus on introducing estimation results obtained at the 97 km altitude. For the tides of each frequency, the migrating and nonmigrating components were examined separately to identify their respective contribution to the whole of the tides. The primary results showed that migrating component plays dominant role in charactering the general temporal and spatial distribution for both diurnal and semidiurnal tides. Regarding the diurnal tides, contribution of migrating component is the most dominant one during spring equinox, which is characterized by the amplitude maxima at the equator and that at the tropics for both hemispheres. Moreover, the temporal variation of the diurnal tides at the tropical latitude in Northern hemisphere is consistent to the analysis result obtained by using meteor radar wind measurements taken in Wuhan （30°N, 114°E）. Contributions of nonmigrating tides are more significant in other seasons. During summer solstitial time in 2005, tidal modes （1, 0）, （1, - 3） and （1, - 2） contribute together to form a diurnal tides active area from 20°N to 40°S with the maximal amplitude 20 K at the equator.Due to the domination of migrating component, semidiurnal tides occur at the tropical latitudes in both hemispheres. In northern hemisphere, the active tides area centers at autumn equinox with maximum 13 K. And in southern hemisphere, the active area centers at the time in between spring and summer equinox. The influences of nonmigrating semidiurnal components are also clear during other seasons as several other centers with maximal amplitude are seen. Confined in the latitude range 40°S - 40°N, terdiurnal components exhibit much weaker activity with much smaller amplitudes than that of the diurnal and semidiurnal components. Current estimation results suggest that nonmigrating terdiurnal components have amplitudes that are as large as and during most times larger than that of migrating component, thus predominate the global distribution of terdiurnal tides in 2005.