共查询到20条相似文献，搜索用时 31 毫秒
1.
F. Chane-Ming F. Molinaro J. Leveau P. Keckhut A. Hauchecorne 《Annales Geophysicae》2000,18(4):485-498
The capabilities of the continuous wavelet transform (CWT) and the multiresolution analysis (MRA) are presented in this work to measure vertical gravity wave characteristics. Wave properties are extracted from the first data set of Rayleigh lidar obtained between heights of 30 km and 60 km over La Reunion Island (21°S, 55°E) during the Austral winter in 1994 under subtropical conditions. The altitude-wavelength representations deduced from these methods provide information on the time and spatial evolution of the wave parameters of the observed dominant modes in vertical profiles such as the vertical wavelengths, the vertical phase speeds, the amplitudes of temperature perturbations and the distribution of wave energy. The spectra derived from measurements show the presence of localized quasi-monochromatic structures with vertical wavelengths <10 km. Three methods based on the wavelet techniques show evidence of a downward phase progression. A first climatology of the dominant modes observed during the Austral winter period reveals a dominant night activity of 2 or 3 quasi-monochromatic structures with vertical wavelengths between 1/2 km from the stratopause, 3/4 km and 6/10 km observed between heights of 30 km and 60 km. In addition, it reveals a dominant activity of modes with a vertical phase speed of –0.3 m/s and observed periods peaking at 3/4 h and 9 h. The characteristics of averaged vertical wavelengths appear to be similar to those observed during winter in the southern equatorial region and in the Northern Hemisphere at mid-latitudes. 相似文献
2.
Observations made with the co-located Rayleigh lidar and MST radar systems at Aberystwyth (52.4°N, 4.1°W) in Wales and radiosondes from Valentia (51.9°N, 10.2°W) in Eire are used to investigate the changes in the vertical propagation of gravity waves during periods of 4 days in June 1995 and February 1993. In each month, the lidar observations show that the wave activity in the upper stratosphere and lower mesosphere changes between two pairs of days. The radar and radiosonde measurements indicate that mountain waves make no contribution to the changes in intensity. Instead, the changes seem to arise largely from the presence or absence of long-period waves with vertical wavelengths near 8 and 10 km in June and February, respectively. The influence of such waves on the vertical wavenumber spectra is examined and related to the evidence for convective instabilities provided by the temperature profiles. 相似文献
3.
K.N. Uma Karanam Kishore Kumar T. Narayana Rao 《Journal of Atmospheric and Solar》2011,73(7-8):815-824
A powerful VHF radar observed characteristics of Convectively generated Gravity Waves (CGW) excited during the wet and dry spells of Indian summer monsoon over a tropical station Gadanki (13.5°N, 79.2°E) are discussed. The characteristics of gravity waves in the lower stratosphere during these two spells are discussed in terms of their wavelet spectra along with height–time sections of vertical velocity. A total of 31 events are analyzed and in more than 50% of the events, the lower stratospheric gravity wave amplitudes were found to be relatively large in dry spell compared to that in the wet spell. The wavelet analysis of lower stratospheric vertical velocities showed a dominant periodicity of about ～20–40 min in wet spell and ～10–20 min in dry spell. The analysis also indicates that wet spell is found to be more conducive for the generation of gravity waves. However, the propagation of these waves into the stratosphere is found to be more efficient in dry spell of monsoon. The strengthening/weakening of the tropical easterly jet during wet/dry spell of monsoon is found to be the main reason for the inhibited/enhanced wave activity in the lower stratosphere during wet/dry spell. The present analysis also suggests that the static stability of the mid- and upper-troposphere during these two spells have implications in the observed frequency of the CGW. Thus, the present analyses brought out for the first time the features of CGW during two distinctive regimes of convective systems and emphasized the importance of prevailing background conditions in exciting/filtering them. 相似文献
4.
为了分析台风这类强对流诱发平流层重力波的过程,本文利用中尺度数值模式WRF-ARW(V3.5)和卫星高光谱红外大气探测器AIRS数据对2011年第9号强热带气旋"梅花"的重力波特征进行了分析.首先,针对模式输出的垂直速度场资料的分析表明,台风在对流层各个方向上几乎都具有诱发重力波的能量,而在平流层内则呈现出只集中于台风中心以东的半圆弧状波动,且重力波到达平流层后其影响的水平范围可达1000km.此外,平流层波动与对流层雨带在形态、位置以及尺度上均具有一定的相似性.其次,对风场的分析结果表明,不同高度上波动形态的差异主要是由于重力波垂直上传的过程中受到了平流层向西传的背景风场以及风切变的调制作用,揭示了重力波逆着背景流垂直上传的特征.随后,基于FFT波谱分析的结果表明,"梅花"诱发的平流层重力波水平波长中心值达到了1000km,周期在15~25h,垂直波长主要在8~12km.最后,利用AIRS观测资料分析了平流层30~40km高度上的大气波动,得到了与数值模拟结果相一致的半圆弧状波动.对比结果也验证了WRF对台风诱发平流层重力波的波动形态、传播方向、不同时刻扰动强度的变化以及影响范围的模拟效果.此外,也揭示了多资料的结合对比有助于更加全面地了解台风诱发平流层重力波的波动特征. 相似文献
5.
本文利用中国科学院空间科学与应用研究中心的瑞利激光雷达首次观测到了平流层地形重力波活动的现象,并结合美国国家环境预报中心(NCEP)的全球预报系统(GFS)的风场数据分析了该地形重力波的基本参数.与惯性重力波相比较,地形重力波的密度扰动没有下传的相位,在同一高度上,其扰动相位保持不变.北京空间科学与应用研究中心瑞利激光雷达自2012年开始观测实验以来,已经观测到多起地形重力波活动事件.本文以2013年11月11日的观测数据为例,研究北京上空的地形重力波活动,并结合GFS风场数据分析了北京上平流层地形重力波的波长、传播方向、传播速度等参量.通过分析得到在2013年11月11日北京上空存在一列传播方向为北偏西52.4°,水平波长为5.5km,平均垂直波长约为6.0km的地形重力波. 相似文献
6.
The nonlinear effects on the characteristics of gravity wave packets: dispersion and polarization relations 总被引：6，自引：0，他引：6
By analyzing the results of the numerical simulations of nonlinear propagation of three Gaussian gravity-wave packets in isothermal atmosphere individually, the nonlinear effects on the characteristics of gravity waves are studied quantitatively. The analyses show that during the nonlinear propagation of gravity wave packets the mean flows are accelerated and the vertical wavelengths show clear reduction due to nonlinearity. On the other hand, though nonlinear effects exist, the time variations of the frequencies of gravity wave packets are close to those derived from the dispersion relation and the amplitude and phase relations of wave-associated disturbance components are consistent with the predictions of the polarization relation of gravity waves. This indicates that the dispersion and polarization relations based on the linear gravity wave theory can be applied extensively in the nonlinear region. 相似文献
7.
Jia Yue Chiao-Yao She Takuji Nakamura Sean Harrell Tao Yuan 《Journal of Atmospheric and Solar》2010,72(1):7-18
On 9 October 2007, long-horizontal-wavelength gravity waves were observed for the first time to steepen and form mesospheric bores at the altitude of ～87 km, by an all-sky OH imager located at Fort Collins (41°N, 105°W), Colorado. The collocated sodium lidar simultaneously observed the presence of a temperature inversion layer as the ducting region. One mesospheric bore uniquely later evolved into a large-amplitude soliton-like perturbation. When the gravity wave and the associated soliton-like perturbation passed through the lidar beams, the lidar detected strong vertical disturbance at 90 km, indicating convective instability. A large cold front system recorded several hours before in the troposphere was aligned to phase fronts of these large gravity waves. For all of the 7 mesospheric bores observed over a 5 year period, we found a similar alignment with a cold front 1000–1500 km away as the likely source of these large-scale gravity waves. 相似文献
8.
《Journal of Atmospheric and Solar》2008,70(10):1281-1288
Simultaneous and complete temperature profiles from near ground to about 100 km are essential for studying the dynamical coupling between different atmospheric layers. They are acquired by combining three different lidar techniques at Wuhan, China (30.5°N, 114.4°E). The atmospheric temperatures from about 3 to 25 km are calculated from the nitrogen molecule density profiles obtained from the N2 vibrational Raman backscatter, while the atmospheric temperatures between 30 and ∼75 km are calculated by the standard Rayleigh scattering method. The temperatures in the 80–100 km altitude region are derived from the Fe Boltzmann technique. The temperature profiles measured by our lidar systems exhibit good agreement when compared with the radiosonde and satellite data, as well as the model. A Lomb–Scargle spectral analysis of the normalized temperature perturbations in the altitude range from 4 to 60 km shows that the spectral slopes of the vertical wave number spectra tended to −3 for large vertical wave numbers. This is consistent with the model predictions of saturated gravity wave spectra. 相似文献
9.
利用非对称波分量分解和小波分析的方法,对准平衡动力模型下非对称强飓风内中尺度波动的空间结构和时间序列特征进行分析.结果表明,平衡流场中1波扰动占主要地位且具有涡旋Rossby波的典型结构特征,准平衡流各波数下扰动的空间分布反映了中尺度波动的混合性质;模式大气和准平衡垂直运动的全局功率谱中,超过信度检验的强波动信号中不仅包含分别表征重力波和涡旋Rossby波的高频和低频波动信号,还存在表征具有物理性质不可分特性的混合涡旋Rossby-重力波的中频波动.混合波的出现建立了不同频段波动之间的能量交换通道,其信号的变化对飓风系统的强弱变化具有一定的指示作用.非平衡垂直运动的波动强信号则主要集中在高频和低频区域,反映了在飓风强度变化情况下,与高频重力波有关的快波调整过程所引起的垂直扰动的振荡和传播.强垂直风切变对飓风内中尺度波动的切向和径向传播具有重要影响,当环境垂直风切变很强时,准平衡1波扰动在径向和切向方向上均呈"驻波"形态,随着环境垂直风切变的减弱,1波扰动以混合波波速逆基本气流传播. 相似文献
10.
《Journal of Atmospheric and Solar》2008,70(7):991-1011
Using the technique developed by Gardner and Voelz [1987. Lidar studies of the nighttime sodium layer over Urbana, Illinois, 2. Gravity waves. Journal of Geophysical Research 92, 4673–4693] and a new method proposed by us, two groups of gravity wave parameters are extracted from 11 years sodium lidar measurements made at a southern low-latitude location. The wave occurrence frequencies, wave parameter distributions, and wave parameter relationships are given and compared with other lidar observations. The different lidar derived results can be attributed to different atmospheric parameters. The characteristics of these two groups of gravity waves are also compared, as well as that predicted by diffusive filtering theory, and we find the gravity wave relationships derived from our method are in better agreement with diffusive filtering theory predictions. 相似文献
11.
Sri Atmaja P. Rosyidi Mohd Raihan Taha Zamri Chik Amiruddin Ismail 《Acta Geophysica》2009,57(3):616-635
Surface wave method consists of measurement and processing of the dispersive Rayleigh waves recorded from two or more vertical
transducers. The dispersive phase data are inverted and the shear wave velocity versus depth is obtained. However, in case of residual soil, the reliable phase spectrum curve is difficult to be produced. Noises
from nature and other human-made sources disturb the generated surface wave data. In this paper, a continuous wavelet transform
based on mother wavelet of Gaussian Derivative was used to analyze seismic waves in different frequency and time. Time-frequency
wavelet spectrum was employed to localize the interested seismic response spectrum of generated surface waves. It can also
distinguish the fundamental mode of the surface wave from the higher modes of reflected body waves. The results presented
in this paper showed that the wavelet analysis is able to determine reliable surface wave spectrum of sandy clayey residual
soil. 相似文献
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利用2011年秋季无线电探空数据,采用矢端曲线法首次分析了新疆库尔勒地区下平流层重力波特征参量,得到36组准单色重力波的结果.结果统计显示：库尔勒秋季下平流层重力波垂直波长、水平波长平均值分别为2.8 km和580 km,固有频率平均值为1.74f.垂直传播方向以上传为主,约占78%,其中下传重力波水平波长较短,固有频率较高.水平传播方向以西北和东南为主,各占1/3,其中上传（下传）重力波水平传播方向以西北（东南）居多,这与热带低纬站点和其他中纬站点观测结果不同.与其他站点比较,库尔勒地区ŵ/f最小,中高纬地区水平波长、垂直波长随纬度增加大致有减小的趋势,库尔勒地区偏离这一趋势,波长偏大. 相似文献
14.
激光雷达观测得到的密度、温度等数据被广泛应用于大气重力波研究.瑞利激光雷达可以获取激光路径上的大气密度、温度数据.对于大气中的三维波动而言,单条路径上的观测参量能提取得到的波动信息有限.本文首先以单色重力波为例,分析了利用激光雷达直接观测三维波动结构的可行性.激光雷达垂直观测即可得到重力波的垂直波长,当激光雷达以一定的天顶角斜向测量时,所得到的波长包含了重力波的垂直波长以及水平波长信息.因此,利用激光雷达同时以三个方向(垂直、向南(天顶角30°)以及向西(天顶角30°))测量,可以提取得到重力波的垂直波长和水平波长.本文利用中国科学院国家空间科学中心研制的车载532nm瑞利激光雷达的经向系统和纬向系统同时以不同的指向角观测大气重力波,对利用激光雷达获取三维波动结构的方法进行了分析研究.本文给出了北京地区激光雷达观测重力波的诸多案例,分析了30~60km高度范围内北京地区大气重力波的垂直及水平波长信息.并以2017年11月7日观测的准单色重力波为例,结合再分析资料的风场数据,分析了该重力波的水平波长,垂直波长及传播方向等信息. 相似文献
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《Journal of Atmospheric and Solar》2003,65(6):765-777
Planetary wave activity at quasi 16-, 10- and 5-day periods has been compared at various altitudes through the middle and upper atmosphere over Halley (76°S, 27°W), Antarctica, during the austral winters of 1997–1999. Observational data from the mesosphere, E-region ionosphere and F-region ionosphere have been combined with stratospheric data from the ECMWF assimilative operational analysis. Fourier and wavelet techniques have shown that the relationship between planetary wave activity at different altitudes is complex and during the winter eastward wind regime does not conform to a simple combination of vertical planetary wave propagation and critical filtering. Strong planetary wave activity in the stratosphere can coincide with a complete lack of wave activity at higher altitudes; conversely, there are also times when planetary wave activity in the mesosphere, E-region or F-region has no apparent link to activity in the stratosphere. The latitudinal activity pattern of stratospheric data tentatively suggests that when the stratospheric signatures are intense over a wide range of latitudes, propagation of planetary waves into the mesosphere is less likely than when the stratospheric activity is more latitudinally restricted. It is possible that, on at least one occasion, 16-day planetary wave activity in the mesosphere may have been ducted to high latitudes from the lower latitude stratosphere. The most consistent feature is that planetary wave activity in the mesosphere is almost always anti-correlated to planetary wave activity in the E-region even though the two are in close physical proximity. The oscillatory critical filtering of vertical gravity wave propagation by planetary waves and the re-generation of the planetary wave component at higher altitudes through subsequent critical filtering or breaking of the gravity waves may provide an explanation for some of these characteristics. Alternatively the nonlinear interaction between planetary waves and tides, indicated in the E-region data, may play a role. 相似文献
17.
T. B. Yanovskaya 《Izvestiya Physics of the Solid Earth》2017,53(6):819-824
Based on the theory of surface waves in a media with weak lateral heterogeneities, an explanation is given for the peculiarities that are considered as prospecting indicators in the microseismic sounding method (MSM). According to this theory, during the propagation of surface waves in such media, their local characteristics are the same as in the case of propagation in a horizontally homogeneous medium characterized by the same vertical velocity section as underlying a given point. Since the wave energy flux through a semiinfinite vertical strip is conserved, the amplitude of the wave is redistributed along the vertical. Based on this principle and simple physical considerations, it is shown that above a low-velocity domain, the amplitudes of microseisms should increase at wavelengths approximately exceeding the depth of the anomaly by a factor of three and decrease at small wavelengths. The model calculations show that variation of spectral amplitudes only allows a depth to the anomaly to be estimated rather than its average extent. Practically identical spectra characterize the anomalies in which the product of the vertical extent of the anomaly and the velocity contrast is approximately similar. 相似文献
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本文利用中尺度数值模式WRF对2003年7月4-5日淮河流域特大暴雨过程进行了数值模拟,并利用高时空分辨率模拟结果资料,提取了暴雨中心区大气重力波频率、周期、水平波长、垂直波长、水平相速和群速等特征参数,分析了暴雨过程中重力波参数随时间的演变特征.结果表明,对此次暴雨强降水过程影响较大的重力波主要是发展的中 α 尺度波和中 β 尺度波,暴雨后期随着重力波的频散,周期和水平波长有减小趋势,频率有增大趋势.非降水区的重力波参数特征和降水中心区有明显不同,大气中小振幅的中 α 尺度和中 β 尺度重力波是否发展和暴雨强降水的发生关系密切. 相似文献
20.
利用子午工程海南激光雷达对我国海南地区上空进行持续观测,通过3年的累积观测数据对我国低纬度地区重力波活动的季节分布特性进行研究,依据重力波线性理论对海南地区上空的大气密度扰动规律、空间功率谱及时间频率谱进行分析,并通过选择波长在1km至8km范围内具有特定波长以及具有波动周期为60 min至25min的特定频率的重力波辅助研究大气密度扰动的季节变化规律,总结得出海南地区重力波活动具有夏季大、春秋季小、而冬季依然频繁的季节性分布规律.结合海南地区特殊的地理位置与当地季节性气候特征分析得出海南地区上空重力波活动季节性变化的可能原因为青藏高原地形及我国南海地区存在的热带强对流与赤道潜流共同作用的结果. 相似文献