共查询到19条相似文献，搜索用时 203 毫秒
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利用MAC/SINE试验期间Chaff火箭在67~96 km高度范围测量的25 m高分辨率经向和纬向速度数据, 研究经向和纬向速度扰动谱特性. 分析结果显示平均垂直波数谱在波数k = 0.001 m-1附近有一分岔点. 在小于这个分岔点的波数区, 经向速度谱和纬向速度谱有接近相同的谱斜率、谱振幅和特征垂直波长, 并且与线性饱和谱模式相当一致. 然而, 在大于这个分岔点的波数区, 经向和纬向速度扰动谱不但谱斜率和谱振幅不一样, 而且它们的谱结构也不相同. 这些差异提供了平均意义上速度扰动场在大波数区各向异性的观测证据. 相似文献
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利用北京市观象台2002年1～12月气球无线电探空观测的垂直高度分辨率为50m的温度观测数据,研究1．67—8．02和13．57～19．92km高度区间归一化温度扰动垂直波数谱,并将它们和线性饱和模式比较．结果表明,单个垂直波数谱的谱斜率和谱振幅存在相当大变率,这和线性饱和理论的预期不一致．然而,在对流层的不同季节和不同地方时观测的平均垂直波数谱显示了很好的类似,即谱斜率非常接近于理论值-3．0,谱振幅和浮力频率的4次方成比例关系,认为对流层季平均谱很好地遵循线性饱和模式,并且在目前是唯一的．相反,在下平流层,平均垂直波数谱的谱斜率与理论值有较好的一致,但观测谱的谱振幅却明显偏离了线性饱和模式的理论预期值．这些观测的平均谱在目前也是唯一的．从对流层和下平流层的平均谱得到的盛行垂直波长在2．1—3．2km之间,与文献中报道的结果大致相同． 相似文献
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利用19枚Chaff火箭测量的水平速度数据和几乎同时发射的19枚Falling sphere火箭测量的温度数据, 研究冬季重力波谱饱和原因. 分析结果显示冬季中层顶区域的不同高度存在大于0.04 s−1的强水平速度切变. 在一个单个Chaff火箭测量中, 在87.4 km高度观测到一个高达0.33 s−1的特强水平速度切变, 这个特强水平速度切变是中层大气曾经测量到的最强水平速度切变. 这些强水平速度切变与从温度剖面得到的Brunt-Väisälä频率平方共同作用产生两个Richardson number小于1/4的动力不稳定区, 表明Chaff火箭在冬季观测到的饱和重力波谱是动力不稳定的结果. 相似文献
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由于测量与计算的难度,对热层垂直中性风的观测还很不够,这影响了人们对热层及热层-电离层耦合的认识.本文基于全天空法布里-珀罗干涉仪(FPI)对热层风场的观测,提出了一种反演垂直中性风的方法.利用该方法,对北极黄河站全天空FPI观测数据进行了垂直中性风的反演计算,结果表明,高热层与低热层的垂直风平均幅值分别在40 m·s-1和15 m·s-1,且垂直风日变化表现出明显的时间演变特性,且与地磁ap指数的变化有一定的相关性,在地磁活动强烈时,低热层垂直风会出现高达100 m·s-1的扰动,高热层甚至会达到300 m·s-1的扰动,这些特征与其他学者的观测结果相一致.本文方法不需要假设垂直风均值为零,也不用限制FPI的观测方位,可用于垂直风的反演. 相似文献
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本文研究声重波在垂直切变风场中传播时谱结构的改变。根据可压缩情况下的流体力学方程组,导出垂直切变风场中大气声重波的谱方程。并指出,这个谱方程是Taylor-Goldstein方程在可压缩和任意垂直波长情况下的推广。由谱方程出发,考虑低边界上的声重波强迫为高斯谱型,采用差分方法,我们计算了ω-KH二维空间中的高层谱响应。结果表明,在具有垂直切变的背景风场作用下,声重波的谱结构发生了改变:1.在原强迫谱所覆盖的谱区段内,一些谱成份被挖除,形成了尖锐的谱峰群;2.最大谱峰发生了偏移;3.波谱变得狭窄。这些变化是垂直切变风场对声重波谱滤波的结果。文中还将上述结论与电离层观测结果进行比较,解释了某些观测现象。 相似文献
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将理想化的南中国海海盆在垂直方向上划分为Ekman层、惯性层和摩擦层. Ekman层中的运动由大气风应力驱动，其底部的扰动压力将作为其下惯性层中运动的上边界条件. 惯性层中的运动是由f 平面三维非线性方程在准地转近似下位势涡度守恒控制，由此得到控制惯性层中运动关于扰动压力的三维椭圆型方程. 在惯性层以下考虑到深层的海盆水平尺度很小，由此引进带有底部摩擦的线性控制方程，方程的边界条件为惯性层和摩擦层交界面上的扰动压力连续，沿海盆边界假定海水与相邻的固壁间无热量交换，由此设在海盆边界上扰动温度为零. 在此基础上分别利用惯性层和摩擦层中的椭圆型控制方程计算了相应层次上冬、夏季的扰动压力和准地转流. 结果表明冬季各层上以气旋式环流为主，且随深度的增加流速减小；夏季各层上以反气旋式环流为主，流速也随深度增加而减小. 这在一定程度上和观测事实相符. 相似文献
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本文同时利用DMSP、ROCSAT-1卫星数据和地基的GPS观测数据,研究一种与低纬等离子体泡相伴随的局部等离子体浓度增强现象.地基GPS的观测表明电离层总电子含量(TEC)也能反映这种等离子体浓度增强.通过4个观测事例的详细分析表明:这种等离子体浓度增强主要出现在磁纬±10°～±20°的局部区域,有时在近磁赤道区和中纬地区的电离层顶部也能观测到;与等离子体泡的出现规律相似,这种等离子体浓度增强主要出现在地方时21∶00以后,并在午夜后也能观测到.当等离子体浓度增强和等离子体泡发生时,在午夜前一般对应着背景垂直速度明显向上的扰动,在午夜后一般处于等离子体垂直速度下降至反向前的时间段,表明东向电场对于低纬不规则体的产生有非常重要的作用. 相似文献
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PKP震相包含了下地幔底部P波速度结构的重要信息.中国地震台网（CSN）台站记录到的南美洲地震的PKP波的射线，对中太平洋下的D″层有很好的采样.本研究采用这些PKP波的AB和DF两个分支的走时差，研究了中太平洋下地幔底部P波速度的小尺度变化.AB DF的走时差减小了上地幔横向不均匀性的影响，而对下地幔底部P波速度的横向变化十分敏感.与此同时，AB DF的走时差也减小了地震定位误差的影响，消除地震发震时间测定误差的影响.本研究的结果表明，在中太平洋的地幔底部存在着大范围的AB DF走时正残差，也即低速异常区，这可能是太平洋下超大地幔热柱的源处.观测到的P波速度异常的空间分布总体上与Grand通过层析成像得到的CMB的S波的速度异常相一致，并在变化的幅度上很好地相关，P波速度的扰动值（在D″层大约为2%）是Grand 速度模型中的S波异常的36%.这一结果有助于太平洋下超大地幔热柱的结构和性质的进一步研究. 相似文献
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Anisotropy of the horizontal velocity fluctuation field in the large wavenumber region 总被引：1，自引：0，他引：1
Mesoscale atmospheric wind, temperature, and density fluctuations are described in terms of their power spectra. In the early 1980s, VanZandt[1] showed that the observed spectrum of the atmospheric fluctuations can result, as in the ocean, from an interna… 相似文献
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RenKang Li Tao Chen Feng Man XiuJie Jiang Jing Luo ZhaoHai He HuiMing Zhang LinFeng Wang Cheng Liu Francisco Carlos de Meneses GuoJun Wang JiYao Xu 《中国科学:地球科学(英文版)》2017,60(4):770-775
A sounding rocket experiment undertaken by the Chinese Meridian Project from a low latitude station on Hainan Island(19.5°N,109.1°E),China,measured the DC electric field during 05:45-05:52 LT on April 5,2013.The data observed using a set of electric field double probes,as part of the rocket's scientific payload,revealed the special profile of how the vectors of the DC electric field vary with altitude between 130 and 190 km.During the experiment,the vertical electric field was downward,and the maximum vertical electric field was nearly 5.1 mV/m near the altitude of 176 km.The zonal electric field was eastward and slightly less than 0.6 mV/m.The plasma drift velocity was estimated from the E×B motion,and the zonal drift velocity was eastward and of the order of 100 m/s.The zonal wind velocity was also estimated using the drift velocity near the maximum density height in the F1-region,and it was found to be nearly 120 m/s.This work constituted the first in situ measurement of the DC electric field conducted within the Fl-region(between 130 and 190 km) in the East Asian Sector. 相似文献
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Shoichiro Fukao Manabu D. Yamanaka Hiromasa Matsumoto Toru Sato Toshitaka Tsuda Susumu Kato 《Pure and Applied Geophysics》1989,130(2-3):463-479
Vertical and temporal variations of three-dimensional wind velocity associated with an upper-tropospheric cold vortex-tropopause funnel system were observed by an MST radar in Japan (the MU radar). Marked changes of vertical velocity and horizontal wind direction were found between the inside and outside of the cold vortex. The vertical velocity activity outside the vortex was asymmetric; it was most active in a sector before the vortex. Unsaturated internal gravity waves in their generation stage contribute predominantly to the vertical velocity activity, suggesting that tropospheric occluded cyclones may be a possible source of middle-atmospheric gravity waves through the geostrophic adjustment process. 相似文献
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An RH-560 rocket flight was conducted from Sriharikota rocket range (SHAR) (14°N, 80°E, dip 14°N) along with other experiments, as a part of equatorial spread F (ESF) campaign, to study the nature of irregularities in electric field and electron density. The rocket was launched at 2130 local time (LT) and it attained an apogee of 348 km. Results of vertical and horizontal electric field fluctuations are presented here. Scale sizes of electric field fluctuations were measured in the vertical direction only. Strong ESF irregularities were observed in three regions, viz., 160/190 km, 210/257 km and 290/330 km. Some of the valley region vertical electric field irregularities (at 165 km and 168 km), in the intermediate-scale size range, observed during this flight, show spectral peak at kilometer scales and can be interpreted in terms of the image striation theory suggested by Vickrey et al. The irregularities at 176 km do not exhibit any peak at kilometer scales and appear to be of a new type. Scale sizes of vertical electric field fluctuations showed a decrease with increasing altitude. The most prominent scales were of the order of a few kilometers around 170 km and a few hundred meters around 310 km. Spectra of intermediate-scale vertical electric field fluctuations below the base of the F region (210/257 km) showed a tendency to become slightly flatter (spectral index n = –2.1 ± 0.7) as compared to the valley region (n = –3.6 ± 0.8) and the region below the F peak (n = –2.8 ± 0.5). Correlation analysis of the electron density and vertical electric field fluctuations suggests the presence of a sheared flow of current in 160/330 km region. 相似文献
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Summary Vertical velocities at the 800, 600 and 400 mbar surfaces over India have been calculated, making use of a 3-level geostrophic baroclinic model. Further, the effects of non-adiabatic heating is included into the model and vertical velocity due to diabatic heating is obtained for the same period. A numerically obtained vertical velocity field due to baroclinicity and diabatic heating is seen to be in agreement with the observed weather patterns. 相似文献
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Array measurements of microtremors were carried out at thirty sites in Damascus city, Syria to estimate S-wave velocity structures of shallow soil formations for site effect analysis. The microtremor data were recorded by 6 vertical-component seismometers distributed along the circumferences of two circles as well as a 3-component seismometer deployed in the center. The phase velocities were estimated at each site from the vertical components of recorded microtremor data by using the Spatial Autocorrelation method. Then, Genetic Simulated Annealing Algorithm technique was applied for inversion of the phase velocities to estimate 1-D S-wave velocity structures beneath the sites. The inverted Vs profiles are not uniform in Damascus city and the results show that a shallow soft layer (∼200 m/s) appears in the eastern part of the city as well as the central part along Barada River. This layer controls the amplification distribution in the city with a high amplification mainly observed at the locations having this layer. The inversion results also show that the depth to the engineering bedrock (∼750 m/s) is very shallow along the foothills of Mt. Qasyoun in the north-west. Then the depth increases towards the east and the south. The maximum depth to the engineering bedrock (∼80 m) was observed in the southern part of Damascus. To validate the results of the inversions, the spectral ratios between the horizontal and vertical components (H/V) of the recorded microtremor data at the central seismometer were compared with the computed ellipticities of the fundamental-mode Rayleigh-waves based on the respective Vs structure. The results show a good agreement in a period range of 0.05 s to 0.5 s. In this period range, the dominant peaks of the H/V ratios are due to the overall effect of the velocity contrasts between the shallow layers representing the subsurface S-wave velocity structure. Moreover, the average S-wave velocity for the top 10 m of soils (VS10) shows a better correlation with the averaged site amplification in a period range of 0.05 s to 0.5 s than VS30 which indicates that VS10 can be a better proxy for high-frequency site amplification in the case of Damascus city. 相似文献
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WU Yongfu & XU Jiyao Laboratory for Space Weather Center for Space Science Applied Research Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2005,48(10)
Gravity waves play a significant role in establishing the large-scale circulation and structure of the middle atmosphere. Through gravity wave saturation proc-esses, such motions are believed to cause turbulence, resulting in divergence of momentum flux and the diffusion of heat and constituents in the meso-sphere[1,2]. The mechanisms that contribute signifi-cantly to the gravity wave saturation are thought to be the dynamical and convective instabilities[3]. However, it is difficult to distin… 相似文献