共查询到20条相似文献，搜索用时 193 毫秒
1.
利用位于中国中纬地区6个OH气辉成像仪2012年1月至2013年12月两年的观测数据,我们研究分析了重力波传播特征.结果表明重力波的水平波长、观测周期和水平相速度分别主要分布于10~35km,4~12min和30~100m·s-1范围.夏季,重力波主要沿极向方向传播.然而,冬季,他们有向赤道方向和平行于赤道方向的传播趋势.同时,我们结合TRMM卫星和ECMWF数据,发现在夏季重力波的北向传播趋势可能主要由观测台站南方的对流活动导致.然而,对流层顶附近的急流可能在冬季重力波的主要传播方向方面做出较大贡献.分析结果也表明,低层-中层大气背景风的滤波效应仅在夏季与中国中纬地区重力波纬向传播方向各向异性吻合较好. 相似文献
2.
采用包括耗散的射线跟踪方法，计算了在水平不均匀风场作用下，不同尺度重力波从对流层直至220km观测高度的传播，结果表明，垂直于重力波传播方向的风以及风剪切能够引起波射线的折射，从而导致重力波明显偏离初始传播方向.在强顺风场作用下，由于风场引起的捕获，大量重力波不能传播到观测高度.由于风场引起的多普勒频移，小周期的重力波在弱顺风条件下能够传播到观测高度.由于反射作用，强逆风场不支持周期低于约18min的较高频重力波的传播.而在弱逆风作用下，大部分中尺度范围重力波都能够传播到观测高度.本文统计了武汉电离层观象台的TID观测数据随热层风场的分布，统计结果与模拟结果符合较好. 相似文献
3.
应用二阶算子分裂格式,采用全非线性模式,对可压大气中重力波波包非共振激发进行数值模拟和分析.研究表明：两个向上传播的重力波波包,通过非共振相互作用,也能激发出一个向下传播的重力波波包.生成波的能量几乎正比于主波的能量,也随次波的能量增大而增大.能量传递方向主要表现为从高频的主波向次波和生成波转移,这与共振相互作用不完全相同.非共振作用的特征时间由主次波的初始位置和波长频率决定,与主次波的初始振幅无关.生成波的波矢量并不严格满足弱非线性相互作用理论预言的波矢量匹配条件,而且生成波的波长和频率在传播的过程中会随时间发生变化,这表明了弱非线性相互作用理论的局限性. 相似文献
4.
本文利用AIM卫星搭载的CIPS云图反照率和冰晶粒径数据,从中提取了2007/08南半球和2008年北半球共6489个小尺度重力波活动(波长5~150km范围)个例,对重力波区域与背景云层冰晶粒径谱进行对比分析,从而研究重力波对冰晶平均半径和谱宽的影响规律.结果表明,北半球重力波区域冰晶的平均半径和谱宽分别比背景云层小2.5nm和6.1nm,南半球则分别减小1.1nm和7.9nm.在随纬度的分布上,小于80°时,南北半球的平均半径扰动值均为负值,绝对值随纬度增大而减小,而大于80°时,负扰动转变为正扰动,且绝对值增加;谱宽扰动的绝对值也随着纬度增加而减小,但均为负值.在季节内随时间的分布上,南北半球重力波对冰晶平均半径和谱宽的扰动在始末阶段以负值为主,且绝对值较大,而在中期阶段正负值相当,且绝对值较小.这一特征与重力波引起冰晶粒径变化的振幅在纬度和时间上的分布趋势一致.重力波的波长均随纬度升高而减小,在季节的始末阶段较大,中期小,且南半球的平均波长和变化幅度都要明显大于北半球的,粒径扰动振幅随波长的变化率为南半球0.207nm·km-1,北半球的0.163nm·km-1.根据分析推断,重力波自身的扰动振幅应与其影响区域内的谱参数相对于背景云层的变化量有直接关系,且振幅越大,平均半径和谱宽的负扰动就越大. 相似文献
5.
给出了重力波在中层大气温度波导中的反对称形式导制传播的线性理论模型,并采用二维非线性的数值模型对重力波波包在中层大气温度波导中的传播和演变过程进行了模拟研究.模拟的结果表明,下层大气激发的重力波能量进入波导区域后被俘获形成导制传播.重力波在波导内不停地来回反射,垂直方向的自由传播受到限制,能量在波导内沿着水平方向传输,模拟得到的波参数与理论值相近.重力波包在温度波导中传播时伴随着能量泄漏,且能量泄漏的速率随时间变缓,最终总有部分能量被限制在波导区域.重力波在水平方向上传播几百公里后,依然维持着良好的波结构,同时数值模拟也给出了重力波在波导区域内能量密度的时空分布. 相似文献
6.
7.
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
8.
使用高灵敏度的电容式微压波传感器对1998年4月11日16时发生在贵州省普定县的一次降冰雹过程的重力波进行观测,利用WRF（Weather Research and Forecast）中尺度模式对这一过程进行数值模拟,使用Morlet小波方法对模拟结果进行分析,得出这一过程中惯性重力波的分布和变化规律,并分析急流、地形及切变线对惯性重力波的影响.观测发现：在降冰雹前,每隔1~4小时出现一次短周期重力波阵性增强的现象.数值模拟结果显示：在低空降冰雹前几个小时有强的短周期重力波出现,其中周期较长的出现早、存在时间长,周期较短的出现晚、存在时间短;强的低空急流和风速垂直切变触发对流或湍流的发生和加强,对流或湍流又激发了80~200 min的短周期重力波;短周期重力波更容易向垂直方向传播,而长周期重力波倾向于水平方向传播.长周期重力波在降冰雹后周期有明显变短现象,随高度越加明显.由地形形成的重力波在最高山峰上空振幅最大. 相似文献
9.
采用二维可压缩大气中重力波非线性传播的数值模式, 研究了重力波与潮汐之间的非线性相互作用. 结果表明, 重力波在潮汐背景中传播时, 先后在z = 75~85, z = 90~110和z = 15~130 km 3个高度上发生不稳定. 垂直波长首先由12 km变成27 km左右, 新生成的长波逐渐被压缩并再次生成20 km左右的长波. 长波和短波出现的高度分别对应于反向和同向背景风场区域的高度. 在重力波主要的破碎区域(90~110 km)以上, 仍有部分重力波继续上传. 重力波在上传过程中除了对背景风场加速之外, 还增大了潮汐的振幅, 特别是在重力波发生不稳定之后, 对潮汐振幅的放大作用更加明显. 相似文献
10.
利用位于海南富克(19.5°N,109.1°E)和广西桂平(23.4°N,110.1°E)两个台站两年多的OH全天空气辉成像仪观测数据,对中国低纬地区的重力波传播统计特征进行了研究.从富克和桂平的气辉成像观测中, 分别提取了65和86个重力波事件.研究结果表明,观测水平波长,观测周期和水平相速度分别集中分布在10~35 km, 4~14 min和20~90 m·s-1范围.重力波传播方向,在夏季表现出很强的东北方向传播.然而,在冬季主要沿东南和西南方向传播. 同时,结合流星雷达风场观测和TIMED/SABER卫星的温度数据,也发现在中层-低热层中传播的大多数重力波表现为耗散传播.且低层-中层大气中背景风场的滤波作用和多普勒频移可能对纬向方向传播的重力波产生的各向异性起到重要的调制作用.然而,经向方向传播的重力波产生的各向异性可能同时被低层大气中波源的非均匀分布以及潮汐变化所影响. 相似文献
11.
The troposphere and lower stratosphere (TLS) is a region with active atmospheric fluctuations. The Wuhan Mesosphere-Stratosphere-Troposphere (MST) radar is the first MST radar to have become operational in Mainland China. It is dedicated to real-time atmospheric observations. In this paper, two case studies about inertia gravity waves (IGWs) derived from three-dimensional wind field data collected with the Wuhan MST radar are presented. The intrinsic frequencies, vertical wavelengths, horizontal wavelengths, vertical wavenumber spectra, and energy density are calculated and analyzed. In this paper, we also report on multiple waves existing in the lower stratosphere observed by the Wuhan MST radar. Lomb-Scargle spectral analysis and the hodograph method were used to derive the vertical wavenumber and propagation direction. Meanwhile, an identical IGW is observed by Wuhan MST radar both in troposphere and lower stratosphere regions. Combining the observations, the source of the latter IGW detected in the TLS would be the jet streams located in the tropopause region, which also produced wind shear above and below the tropopause. 相似文献
12.
Inertia-gravity waves in the troposphere and lower stratosphere associated with a jet stream exit region 总被引：1，自引：0，他引：1
Radar measurements at Aberystwyth (52.4°N, 4.1°W) of winds at tropospheric and lower stratospheric heights are shown for 12–13 March 1994 in a region of highly curved flow, downstream of the jet maximum. The perturbations of horizontal velocity have comparable amplitudes in the troposphere and lower stratosphere with downward and upward phase propagation, respectively, in these two height regions. The sense of rotation with increasing height in hodographs of horizontal perturbation velocity derived for hourly intervals show downwards propagation of energy in the troposphere and upward propagation in the lower stratosphere with vertical wavelengths of 1.7 to 2.3 km. The results indicate inertia-gravity waves propagating in a direction similar to that of the jet stream but at smaller velocities. Some of the features observed contrast with those of previous observations of inertia-gravity waves propagating transverse to the jet stream. The interpretation of the hodographs to derive wave parameters has taken account of the vertical shear of the background wind transverse to the direction of wave propagation. 相似文献
13.
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
14.
The characteristics of different-scale acoustic gravity waves (wavelengths of 100–1200 km, periods of 10–50 min) under different geophysical conditions have been studied using a numerical model for calculating the vertical structure of these waves in a nonisothermal atmosphere in the presence of an altitudedependent background wind and in a situation when molecular dissipation is taken into account. It has been established that all considered acoustic gravity waves (AGWs) effectively reach altitudes of the thermosphere. The character of the amplitude vertical profile depends on the AGW scales. The seasonal and latitudinal differences in the AGW vertical structure depend on the background wind and temperature. A strong thermospheric wind causes the rapid damping of medium-scale AGWs propagating along the wind. Waves with long periods to a lesser degree depend on dissipation in the thermosphere and can penetrate to high altitudes. A change in the geomagnetic activity level affects the background wind vertical distribution at high latitudes, as a result of which the AGW vertical structure varies. 相似文献
15.
本文基于描述可压缩大气静力适应过程的线性模型,分别采用正交模法和WKBJ法,从波动响应的角度研究了风垂直切变对大气静力适应过程的影响.结合实际天气现象构造了四种风垂直切变模型,分别为垂直无切变的定常模型、类似锋面特征的线性切变模型、表征东风急流的反气旋式切变模型和类似西风急流的气旋式切变模型.分析了相应模型下静力适应过程中的波动特征及波能量演变规律.得到结论:(1)在定常模型中,破坏静力平衡的能量激发出四支两两成对的、传播性质类似声波和重力波的波动,波动能量在闭合系统假设下为守恒量;(2)风切变的存在改变了波动及其能量的传播特征,也改变了波动能量的守恒性;(3)在大气稳定层结下,若波动多普勒频率大于0且小于0.7倍的浮力振荡频率,则发展(衰亡)型波动的螺旋结构分别为:(a)在线性切变模型中,等相位线自下而上需向西(东)倾斜;(b)在反气旋式切变模型中,等相位线在急流轴上层自下而上需向西(东)倾斜,在急流轴下层自下而上需向东(西)倾斜;(c)在气旋式切变模型中,等相位线在急流轴上层自下而上需向东(西)倾斜,在急流轴下层自下而上需向西(东)倾斜;若波动多普勒频率大于0.7倍的浮力振荡频率,则情形相反. 相似文献
16.
《Journal of Atmospheric and Solar》2008,70(10):1336-1350
Planetary waves with periods between two and four days in the middle atmosphere over Antarctica are characterized using one year of data from the medium-frequency spaced antenna (MFSA) radars at Scott Base, Rothera, and Davis. In order to investigate the origin of the observed waves, the ground-based data are complemented by temperature measurements from the Earth Observing System Microwave Limb Sounder (EOS MLS) instrument on the Aura satellite as well as wind velocity data from the United Kingdom Met. Office (UKMO) stratospheric assimilation. Observed characteristics of waves with a period of approximately two days in summer are consistent with the quasi-two-day wave (QTDW) generally found after the summer solstice at low- and mid-latitudes. The Scott Base observations of the QTDW presented here are the highest-latitude ground-based observations of this wave to date. Waves with preferred periods of two and four days occur in bursts throughout the winter with maximum activity in June, July, and August. The mean of the two- and four-day wave amplitudes is relatively constant, suggesting constant wave forcing. When several waves with different periods occur at the same time, they often have similar phase velocities, supporting suggestions that they are quasi-non-dispersive. In 2005, a “warmpool” lasts from late July to late August. An alternative interpretation of this phenomenon is the presence of a structure propagating with the background wind. Consideration of the role of vertical shear (baroclinic instabilities) and horizontal shear (barotropic instabilities) of the zonal wind suggests that instabilities are likely to play a role in the forcing of the two- and four-day waves, which are near-resonant modes and thus supported by the atmosphere. 相似文献
17.
南极地区重力波活动有大量报道,相对而言,北极地区重力波的研究还很少.本文利用极区Ny-Alesund站点（78.9°N,11.9°E）无线电探空仪从2012年4月1日到2017年3月31日共5年的观测数据,统计分析了北极地区低平流层惯性重力波的特征.观测显示,月平均纬向风在20 km以下盛行东向风,再随着高度增加,逐渐呈现出半年振荡现象.对流层顶高度在5~13 km范围内变化,其月平均高度显示出年循环,最高出现在夏季,约为10 km,最低出现在冬季,约为8.5 km.对流层和低平流层月平均温度都显示出明显的年周期变化,这与中低纬度观测结果有所不同.结合Lomb-Scargle谱分析和矢端曲线方法,估算了准单色惯性重力波参数.个例研究表明,低平流层惯性重力波呈现出远离源区的自由传播性质.统计结果显示,惯性重力波的水平和垂直波长分别集中在50~450 km和1~4 km范围内,本征频率集中在1~2.5倍惯性频率间,这些值都比中低纬度观测值稍小.垂直方向本征相速度主要集中在-0.3~0 m·s-1,而纬向和经向本征相速度集中在-40~40 m·s-1之间.在5年的观测中,大约91.5%的惯性重力波向上传播.在冬季和早春,由于极地平流层极涡活动,激发出向下传播的惯性重力波,因此,向下传播的比例上升到相应月份的20%左右.由于低层大气盛行的东向风的滤波效应,低平流层大部分惯性重力波向西传播.波能量呈现出明显的年周期变化,最大值在冬季、最小值在夏季,与北半球中低纬度观测结果一致,表明北半球重力波活动普遍冬季强、夏季弱. 相似文献
18.
Nonhydrostatic Atmospheric Normal Modes on Beta-Planes 总被引：1，自引：0，他引：1
--To facilitate the understanding of nonhydrostatic effect in global and regional nonhydrostatic models, the normal modes of a nonhydrostatic, stratified, and compressible atmosphere are studied using Cartesian coordinates on midlatitude and equatorial #-planes. The dynamical equations without forcing and dissipation are linearized around the basic state at rest, and solved by using the method of separation of variables. An eigenvalue-eigenfunction problem is formulated, consisting of the horizontal and vertical structure equations with suitable boundary conditions. The wave frequency and the separation parameter, referred to as "equivalent height," appear in both the horizontal and vertical characteristic equations as a coupled problem, unlike the hydrostatic case. Therefore, the nonhydrostatic equivalent height depends not only on the vertical modal scale, as in the hydrostatic case, but also on the zonal and meridional modal scales. Numerical resu lts on the dispersion relations are presented for an isothermal atmosphere. Three kinds of normal modes, namely acoustic, gravity, and Rossby modes, are solved and compared with the corresponding global solutions. Nonhydrostatic effects are studied in terms of normal modes in a wide range of wavelengths from small to planetary scales. It is demonstrated that Rossby modes are hardly affected by nonhydrostatic effects regardless of wavelengths. However, nonhydrostatic effects on gravity modes become significant for smaller horizontal and deeper vertical scales of motion. The equivalent height plays a particularly important role in evaluating nonhydrostatic effects of normal modes on the equatorial #-plane, because the equivalent height appears in the scaling of meridional distance variable of the eigenfunctions. The implementation of nonhydrostatic normal mode analysis on high-resolution numerical modeling is also discussed. 相似文献
19.
针对长江中下游中尺度地形特点以及暴雨过程发生发展期间风垂直切变的主要观测特征,设计了一系列中尺度地形的三维理想数值试验,分析了干大气地形流和重力波特征,探讨了条件不稳定湿大气地形对流降水的模态分布,在此基础上研究了圆形、直线风垂直切变和切变厚度对中尺度地形对流降水强度和模态分布的影响.结果发现:在 Fr≈1的干大气条件下,气流遇到地形后分支、绕流和爬升现象同时存在,地形激发的重力波在水平和垂直方向上传播,其在迎风坡、背风坡、地形上游和下游的振幅不同,并组织出不同强度的垂直上升运动.在Fr > 1的条件不稳定湿大气下,地形对流降水主要存在三种模态,即迎风坡和背风坡准静止对流降水以及地形下游移动性对流降水,地形对流降水的形成与重力波在低层组织的上升运动密切相关.风垂直切变对地形对流降水的强度和模态分布有重要作用,其中圆形风垂直切变(风随高度旋转)不仅影响地形下游对流降水系统的移动方向,而且影响迎风坡和背风坡山脚处对流降水中心的分布和强度;直线风垂直切变(风随高度无旋转)主要影响地形对流降水的移动速度和强度.风随高度自下而上顺(逆)时针旋转,地形对流系统向下游传播时向右(左)偏移.风垂直切变主要通过影响地形重力波的结构和传播以及对流系统的形成、移动方向和速度,来影响地形对流降水的模态分布,其中对流层中低层的风垂直切变对地形对流降水强度和模态分布有重要影响. 相似文献
20.
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