共查询到19条相似文献，搜索用时 171 毫秒
1.
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
2.
《中国科学:地球科学》2016,(12)
重力波参数特征的确定是全球大气环流模式中平流层重力波参数化的一个重要环节,这些参数的选取需要根据观测资料来确定.本文根据中国地区南北向8个站点(自北向南依次为嫩江、锡林浩特、北京、郑州、南阳、宜昌、怀化和南宁,纬度范围为22°~49°N)两年多的垂直高分辨率无线电探空资料,分析了下平流层(18~25km)惯性重力波活动的季节变化及其随纬度的分布特征.主要结果有:(1)与全球其他地区一样,中国地区下平流层重力波能量具有明显的季节变化和经向分布特征:冬季大夏季小,且随着纬度增加而减小;纬向和经向速度扰动大小一致,表明重力波能量在水平方向上是各向同性的.(2)重力波垂直波长随纬度没有明显变化,集中在1~3km,占所有样本的85%以上,平均值约为2.0km;水平波长80%以上集中在100~800km,平均值约为450km,有随纬度增加而降低的趋势(南北水平波长相差达40km左右),水平波长与垂直波长之比大约为200:1,表明下平流层重力波基本上沿水平方向传播,垂直方向的夹角极小.(3)固有频率和科氏参数之比有随纬度增加而减小的特征,集中在1~2,平均值约为1.5.(4)重力波能量主要向上传播,各站点重力波上传频率均在60%以上;水平传播方向有比较显著的方向性,主要是东西方向传播且与盛行风向有关,但是该各向异性随着纬度的增加有所减弱. 相似文献
3.
对流性重力波对中层大气环境有显著影响.重力波活动及重力波源的地理和季节性变化等信息是理解和模拟重力波效应的基础.卫星高光谱红外大气垂直探测器AIRS的4μm和15μm波段可用于识别30~40km高度范围和41km高度附近的重力波,其11μm通道可同步观测对流层深对流.观测个例表明,海面和陆面上空的平流层扰动影响范围均可达1000km,不同高度的扰动强度分布也存在差异.基于2007年6月至8月的AIRS观测资料,分析了东亚区域的对流层深对流活动和平流层的重力波,得到了深对流和重力波发生频率的水平分布.统计结果表明,东亚区域夏季夜间的深对流活动明显少于白天,但AIRS观测到的平流层重力波发生频率和扰动强度均显著大于白天,揭示了夜间对流层深对流诱发的平流层重力波在强度、范围等方面可能与白天存在显著差异.进一步对比分析表明,AIRS观测的平流层扰动高值区与深对流高值区明显不同.平流层重力波与对流层深对流之间的相关分析表明,在36°N以南的区域,41km高度上AIRS观测的重力波中,深对流云诱发的重力波的比例约为30%~100%.在10°N至36°N区间,90%的深对流均可诱发平流层重力波.分析得到的30~40km高度区间和41km高度附近的重力波水平分布对比表明,后一高度上的扰动强度明显大于前一高度,且前一高度在东南亚区域存在强扰动中心而在后一高度则没有.最后,给出了AIRS观测的几种典型形态的东亚区域平流层波动,表明了该区域平流层环境波动形态的复杂性和多样性. 相似文献
4.
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
5.
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
6.
用垂直高分辨率探空资料分析北京上空下平流层重力波的统计特性 总被引：10，自引：0，他引：10
根据北京市观象台新一代无线电探空垂直高分辨率资料研究北京地区下平流层(17~24 km)惯性重力波活动的季节变化特征. 根据风速以及温度之间的偏振关系来分析重力波的一些重要参数. 结果表明: 1) 波动能量有明显的季节变化, 夏季弱(动能3.5 J/kg, 潜能1.8 J/kg), 冬季强(动能10.6 J/kg, 潜能3.6 J/kg), 全年的动能与潜能比的平均值为2.6; 纬向与经向扰动速度之均方根大小基本一致, 表明下平流层重力波能量在水平方向上是各向同性的. 2) 垂直波长主要集中在1.5~3 km之间, 占所有样本的80%以上, 平均值大致为2.3 km; 水平波长主要集中在100~800 km之间, 平均值为445 km左右; 水平波长与垂直波长之比大约200︰1. 3) 在拟合偏振椭圆前, 采用带通滤波保留垂直波长在1.5~3 km之间的波, 估计得到的固有频率主要集中在1f~3.5f之间(f为科氏参数), 平均值为2f, 相当于周期9 h左右. 4) 重力波能量主要向上传播, 上传重力波出现频率在90%以上; 水平传播方向有一定的不均匀性, 但不是很强, 主要方向为西北方向. 相似文献
7.
利用2003-2011年的SABER/TIMED温度数据观测发现,在2006年、2009年和2010年北半球高纬（70°N）的冬季（1-3月）发生了“平流层顶抬升”.在这3次事件中,1月末-2月初的~50 km和~80 km高度处分别出现了温度的极大值~260 K和~230 K,即平流层顶的高度突然由原来的50 km左右上升至80 km左右,这就是平流层顶抬升事件;随着时间的推移,抬升的平流层顶的高度逐渐下降直至恢复到原有位置,与此同时其温度由~230 K上升至~260 K.值得注意的是,虽然在极区的每年冬天都发生平流层突然增温事件,但是只在伴随着极涡分裂的平流层突然增温事件后出现平流层顶抬升.此外,在发生平流层顶抬升事件的冬季里,高纬的重力波活动在1月末-2月初的~80 km高度处突然增强,对应着平流层顶的抬升时间和高度;在2月份之后,重力波活动在75 km以下逐渐增强、在75 km以上逐渐减弱,同时抬升的平流层顶也不断下降.通过重力波活动与平流层顶抬升事件的相关性分析,表明重力波活动可能对平流层顶的抬升有重要影响. 相似文献
8.
本文利用中纬站点Miramar Nas(32.87°N,117.15°W)的探空数据提取了对流层和低平流层的惯性重力波参数并计算了动量通量-相速度谱.分析表明低层大气重力波动量通量谱很好地满足高斯分布.高斯拟合的参数分析显示:(1)冬季西风急流对向东传播的波的吸收使得对流层向西传播的波的高斯峰值明显强于向东传播的波;(2)重力波在由对流层向平流层的传播过程中谱展会增大,这可能是波与背景相互作用以及波-波相互作用的结果;(3)急流对重力波的吸收与反射以及对流层顶附近波的耗散使得低平流层总动量通量远小于对流层的.受背景风场影响,谱的季节变化呈现出一定规律.多普勒效应对谱产生了两方面的影响,一方面背景风较大时多普勒效应会使谱展宽,另一方面多普勒效应会显著改变谱的中心本征相速度,使得动量通量谱在同一方向上呈现不对称性. 相似文献
9.
本文通过分析美国阿拉斯加地区三个站点(Nome,64.50°N,165.43°W;McGrath,62.97°N,155.62°W;Fairbanks,64.82°N,147.87°W)无线电探空仪1998～2006年观测数据,研究了北半球高纬地区低层大气行星波特性.通过分析发现行星波主要存在于两个区域,一个在对流层顶附近,一个在冬季极夜急流附近,两个区域的行星波都具有明显的间断性,持续时间一般不超过2个月;三个分量中,温度扰动量的振幅最小,经向风扰动量的振幅最大.对流层顶附近的行星波没有明显的季节变化且谱成分较为复杂,5天波的振幅最小,10天波的振幅略强于16天波.极夜急流附近的行星波主要出现在冬季,波振幅比对流层顶附近小,主要为10天波和16天波,且16天波的振幅强于10天波.由折射指数可以看出,夏季在对流层上方有明显反射层,冬季则较弱甚至消失,很好地解释了平流层行星波主要在冬季出现的原因.对2003/2004年冬季三个站点行星波的细致分析发现对流层区域和极夜急流区域出现明显的准10天波和准16天波,准10天在垂直方向为驻波,温度分量垂直波长约为12km,经向风分量垂直波长大于26km,波自东向西传,纬向... 相似文献
10.
使用中尺度数值模式WRF-ARW,针对2010年6月发生在中国东北地区一例伴随对流层高空西风急流（位于~9 km高度）演变过程出现的平流层重力波活动特征开展了数值模拟. 事件发生期间,对流层区域环流处在一个东北冷涡系统的控制之下. 模拟结果再现了该东北冷涡的发展和维持过程,以及与之相伴的高空急流的特征. 模拟结果揭示出在急流区域上空的平流层中存在显著重力波活动现象. 分析结果显示,重力波活动与急流存在紧密联系,在水平方向上,重力波呈显著的二维结构,出现在急流出口区上部并逆背景流向西传播. 功率谱分析结果表明盛行波动具有~700 km水平尺度、9~12 h时间尺度以及4~5 km垂直波长. 由于急流的存在,造成其与平流层中下部之间存在显著的水平风速垂直切变,与切变相伴的耗散使得上传的重力波动量通量数值随着高度升高而递减. 同时,在18~20 km高度间出现的西风-东风转换带极大地抑制了波动在垂直方向的传播,形成显著动量通量沉积效应. 估算结果表明,在11~20 km高度之间,这种效应的整体作用相当于对该层背景流施加强度为0.86 m·s-1·day-1的动力阻曳. 相似文献
11.
Saskatoon (52° N, 107°W) medium frequency (MF) radar data from 1979 to 1993 have been analyzed to investigate the climatology of irregular wind components in the height region 60–100 km. This component is usually treated in terms of internal gravity waves (IGW). Three different band-pass filters have been used to separate the intensities of IGWs having periods 0.2-2.5; 1.5-6 and 2–10 h, respectively. Height, seasonal and inter-annual variations of IGW intensities, anisotropy and predominant directions of propagation are investigated. Mean over 14 years’ seasonal variation of the intensity of long-period IGWs shows a dominant annual component with winter maximum and summer minimum. Seasonal variations of the intensity of short-period waves have a strong semi-annual component as well, which forms a secondary maximum in summer. Predominant azimuths of long-period IGWs are generally zonal, though they vary with season. For short-period IGWs, the predominant azimuth is closer to the meridional direction. Anisotropy of IGW intensity is larger in summer, winter and at lower altitudes. The IGW intensity shows apparent correlation with both solar and geomagnetic activity. In most cases, this correlation appears to be negative. The variations versus solar activity is larger for longer-period IGW. Possible reasons and consequences of the observed climatological variations of IGW intensity are discussed. 相似文献
12.
N. M. Gavrilov 《Annales Geophysicae》1997,15(12):1570-1580
The mechanism of generation of internal gravity waves (IGW) by mesoscale turbulence in the troposphere is considered. The equations that describe the generation of waves by hydrodynamic sources of momentum, heat and mass are derived. Calculations of amplitudes, wave energy fluxes, turbulent viscosities, and accelerations of the mean flow caused by IGWs generated in the troposphere are made. A comparison of different mechanisms of turbulence production in the atmosphere by IGWs shows that the nonlinear destruction of a primary IGW into a spectrum of secondary waves may provide additional dissipation of nonsatu-rated stable waves. The mean wind increases both the effectiveness of generation and dissipation of IGWs propagating in the direction of the wind. Competition of both effects may lead to the dominance of IGWs propagating upstream at long distances from tropospheric wave sources, and to the formation of eastward wave accelerations in summer and westward accelerations in winter near the mesopause. 相似文献
13.
Averaged seasonal variations of wind perturbation intensities and vertical flux of horizontal momentum produced by internal gravity waves (IGWs) with periods 0.2/1 h and 1/6 h are studied at the altitudes 65/80 km using the MU radar measurement data from the middle and upper atmosphere during 1986/1997 at Shigaraki, Japan (35°N, 136°E). IGW intensity has maxima in winter and summer, winter values having substantial interannual variations. Mean wave momentum flux is directed to the west in winter and to the east in summer, opposite to the mean wind in the middle atmosphere. Major IGW momentum fluxes come to the mesosphere over Shigaraki from the Pacific direction in winter and continental Asia in summer. 相似文献
14.
The zonally averaged UK Meteorological Office (UKMO) zonal mean temperature and zonal winds for the latitudes 8.75°N and 60°N are used to investigate the low-latitude dynamical response to the high latitude sudden stratospheric warming (SSW) events that occurred during winter of the years 1998–1999, 2003–2004 and 2005–2006. The UKMO zonal mean zonal winds at 60°N show a short-term reversal to westward winds in the entire upper stratosphere and lower mesosphere and the low-latitude winds (8.75°N) show enhanced eastward flow in the upper stratosphere and strong westward flow in the lower mesosphere during the major SSW events at high latitudes. The mesosphere and lower thermosphere (MLT) zonal winds acquired by medium frequency (MF) radar at Tirunelveli (8.7°N, 77.8°E) show a change of wind direction from eastward to westward several days before the onset of SSW events and these winds decelerate and weak positive (eastward) winds prevail during the SSW events. The time variation of zonal winds over Tirunelveli is nearly similar to the one reported from high latitudes, except that the latter shows intense eastward winds during the SSW events. Besides, the comparison of daily mean meridional winds over Tirunelveli with those over Collm (52°N, 15°E) show that large equatorial winds are observed over Tirunelveli during the 2005–2006 event and over Collm during the 1998–1999 events. The variable response of MLT dynamics to different SSW events may be explained by the variability of gravity waves. 相似文献
15.
本文基于1987—2017年南极点的无线电探空数据,研究了地面至30 km海拔高度的气温、风向和风速的垂直分布及变化趋势.多年平均的逐月数据表明,气温在各高度上均具有显著的季节变化,南半球夏季（冬季）对流层低层温度最高达-25℃（最低达-60℃）,分别出现于1月（7月）地面以上约500 m（近地面）.近30年来,年平均地面气温呈0.3℃/10a的增加趋势,增温趋势总体上随高度增加而减缓,至对流层上层的气温变化趋势为负,约为-0.25℃/10a.对于对流层整层平均气温,秋季上升趋势在四季中最为明显,达0.55℃/10a,而年平均气温的趋势约为0.3℃/10a.近地面全年盛行东北风,风速大多在2~10 m·s-1范围内;对流层的低层（高层）为西北风（西南风）,在海拔6~9 km处,对流层急流可达25 m·s-1;而平流层低层（高层）为南风（东南风）,最大风速可超过30 m·s-1.风速和温度梯度变化特征在地面至10 km（10~30 km）高度段表现为负相关（正相关）.近30年近地面呈现北风增加东风减少的趋势,而高空南风减少,东风和北风增多.对流层整层平均风速显示,各季节平均风速均呈增加趋势,并且与温度类似,秋季的增加趋势最显著,达0.59 m·s-1/10a,而春季趋势最为平缓,仅0.05 m·s-1/10a.对流层整层年平均风速的线性趋势为0.24 m·s-1/10a,地面年平均风速呈0.05 m·s-1/10a的增加趋势. 相似文献
16.
I. V. Karpov F. S. Bessarab O. P. Borchevkina K. A. Artemenko A. I. Klopova 《Geomagnetism and Aeronomy》2018,58(4):509-522
The results of numerical experiments on the modeling of thermospheric and ionospheric disturbances under conditions of sudden stratospheric warming are presented to study the possible mechanisms of such disturbances. Local disturbances caused by a planetary wave with zonal wave number s = 1 and internal gravity waves (IGWs) propagating from the disturbed region in the stratosphere are taken into account as sources of disturbances. It is shown that the inclusion of an additional source of thermospheric disturbances caused by mesospheric variations of atmospheric parameters with IGW periods over the region of sudden stratospheric warming leads to significant changes in the parameters of the thermosphere and ionosphere, including a change in the global structure of the distributions of the gas components of the thermosphere and a shift in maximum concentrations of atomic oxygen to low latitudes of the Southern Hemisphere; there is an increase in the mean values, the diurnal and semidiurnal variations of the ion concentration in the F region of the ionosphere. These features of changes in the parameters of the thermosphere and ionosphere occurred with insignificant disturbances of tidal variations in the thermosphere. 相似文献
17.
本文利用2007年1月至2012年12月的COSMIC卫星温度剖线,从中提取了垂直波长在3~10 km的重力波扰动信息,进而分析了全球平流层大气重力波的分布特征.赤道地区低平流层重力波表现出明显的准两年变化,这种变化与风场的准两年变化具有明显的相关性,向下发展速度约为1 km/月;赤道地区高平流层(35 km以上区域)的重力波活动则存在明显的半年变化.中高纬度重力波活动主要表现为冬季强夏季弱.在南极地区存在着与急流的时间、空间以及强度变化密切相关的重力波分布特征,这说明在南极极夜急流是非常重要的一个重力波源;而在北极极夜急流的作用则没有那么强.此外,通过考察不同高度的重力波活动特征,我们发现:30 km以下重力波活动较强区域主要在赤道地区且与强对流区分布基本吻合,地形诱发的以及与天气系统相关的强重力波活动在该高度范围内同样出现;而在30 km以上的区域重力波活动强度分布则会出现与平流层爆发性增温以及极夜急流有关的变化. 相似文献
18.
《Journal of Atmospheric and Solar》2002,64(8-11):1229-1240
Continuous wind observations allow detailed investigations of the upper mesosphere circulation in winter and its coupling with the lower atmosphere. During winter the mesospheric/lower thermospheric wind field is characterized by a strong variability. Causes of this behaviour are planetary wave activity and related stratospheric warming events. Reversals of the dominating eastward directed mean zonal winds in winter to summerly westward directed winds are often observed in connection with stratospheric warmings. In particular, the amplitude and duration of these wind reversals are closely related to disturbances of the dynamical regime of the upper stratosphere.The occurrence of long-period wind oscillations and wind reversals in the mesosphere and lower thermosphere in relation to planetary wave activity and circulation disturbances in the stratosphere has been studied for 12 winters covering the years 1989–2000 on the basis of MF radar wind observations at Juliusruh (55°N, since 1989) and Andenes (69°N, since 1998). Mesospheric wind oscillations with long-periods between 10 and 18 days are observed during the presence of enhanced planetary wave activity in the stratosphere and are combined with a reversal of the meridional temperature gradient of the stratosphere or with upper stratospheric warmings. 相似文献
19.
《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