2009年1月5日廊坊OH气辉观测图像的谱分析

2009年1月5日在中国河北省廊坊市韩村镇(39.4°N,116.6°E)进行了中国首次中间层顶大气重力波成像观测实验,记录了近4 h的OH气辉辐射数据,给出了依据该数据计算所得的该时间段内廊坊韩村附近水平方向约185 km范围内的中间层顶OH气辉扰动的谱分析结果.所得到的传播方向确定的二维功率谱和角度谱揭示了该时间段内重力波活动的波长和传播方向分布特点,表明波长下限较短,西向传播分量明显大于东向分量.     

一种全天空气辉成像仪数据预处理方法和初步结果

大气重力波是大气中的基本波动形式之一,在中高层大气动力和热力学过程中起着十分重要的作用.全天空气辉成像仪是一种以大气气辉辐射为示踪物,能够有效对大气重力波成像的仪器.本文针对中国科学院国家空间科学中心空间天气学国家重点实验室中高层大气组自主研制的全天空气辉成像仪所观测的数据,提出了一种气辉图像预处理方法,进行平场校正、方位校正、星光去除和坐标映射等数据订正.利用该方法处理2015年5月17日21:00BLT至次日05:00BLT西宁台站（36.6°N,101.7°E）的OH气辉数据,发现一次重力波事件,分析并获得了该重力波的水平波长、观测水平相速度和传播方向（分别为17.72km,47m·s-1,339°）.研究结果表明该方法是可行的.      

对流层雷暴源所产生的柱形重力波

已有充分的证据表明, 大气对流层的雷暴迹象是大气中间层重力波活动的显著代表源.在雷暴迹象的上方, 通过火箭已观测到大气中间层出现的热效应, 也已通过雷 达探测到大气平流层出现的上行重力波, 从地面和卫星平台上观察到夜间气辉有序而 成环状的重力波波形. 所有这些实验结果都与位于观测点下方的雷暴活动有紧密联系. 此类雷暴通常主要集中在中国东部沿海以及地球其他沿海海湾地域. 关于此类雷暴对大 气中间层的影响尚未被充分研究和了解. 为能有效地探究其成因, 利用所开发的一个二维计算机数值模型模拟和研究大气对流层的雷暴源所引发的上行重力波, 进而揭示 此类重力波产生的基本物理机理, 及其在大气中间层的能量耗散. 通过模拟研究发现, 雷暴源可以大面积高强度地聚集和释放积雨云的能量, 当这种周期性的对流变化引发大气对流层的不稳定性后, 就会有圆柱体重力波的产生和传播.      

中国山西地区法布里-珀罗干涉仪测风能力及数据质量检验

介绍了中国气象局山西岢岚大气观测站(39°N, 112°E) 法 布里-珀罗干涉仪(FPI) 的基本 构造、测风能力、程序处理流程、数据质量控制方法以及检验情况. 岢 岚观测站FPI可以观测892.0 (OH)nm, 557.7 (OI)nm和630.0 (OI)nm 波 长处气辉谱线的多普勒移动, 分别计算对应87km, 97km和250km高度处 的大气风速和大气温度, 可给出中间层顶区域及热层风的大气潮汐和扰动 情况. 采用水平风模型(HWM)输出结果进行交叉检验, 对FPI测风数据质量进行验证. 结果显示, 岢岚大气观测站FPI仪器的测风数据 在长期趋势上与HWM模式的输出数据一致, 风速变化幅度有季节性差异, 数据质 量控制方法有效, 测风误差在87km高度处为5.7m·s-1, 97km处 为1.3m·s-1, 250km处为4.1m·s-1, 测风数据 通过了可靠性检验.      

台风激发的声重力波的可探测性研究

通过对北京大学高频多普勒台站(39.4°N,116.2°E)多年的观测资料及相关台风资料的统计分析,着重研究了高频多普勒探测手段对由台风引起的扰动电离层响应的可探测性问题.通过对台风登陆前后的高频多普勒观测记录的细致分析及与宁静条件下记录的对比研究,表明高频多普勒观测手段可以很好地探测由台风激发的声重力波,尤其是对台风登陆前后所激发的扰动具有较高的可探测性.在所分析的24次台风事件中有明显扰动记录的高达22次(22/24).结合观测事实与Huang等的统计结果(2/12)进行了比较,并进行了可能的原因分析.通过数值模拟的方法对观测到的主要扰动的非线性传播过程进行了模拟再现,结果基本上与观测结果及线性传播理论一致.确认了一般情况下高可探测性这一事实,但同时也表明可探测性和台风激发源与探测位置及中尺度TIDs在电离层中的传播模式有密切关系.      

武汉上空惯性重力波活动

利用武汉中心气象台(30.5°N,114.4°E)无线电探空仪在2001年1月到2003年12月之间的观测数据,研究了武汉上空1-9km和14-25km高度范围内惯性重力波参数的变化特征.数据分析结果表明,重力波活动存在明显的季节变化,冬季较频繁,夏季活动较弱,与急流强度的季节变化一致,这意味着重力波的激发与背景风密切相关.矢端曲线分析显示1-9km范围内能量向上传播和向下传播的波的比例大致相同,而14-25km范围内绝大部分波能量向上传播,这与最大急流强度的高度相对应;进一步分析表明,夏天14-25km范围内波几乎全向上传播,而冬天则有相当一部分波向下传播,这可能是反射引起的.重力波的本征频率集中在1-3倍的惯性频率之间,水平波长约数百公里;1-9 km范围内垂直波长集中在3-3.5 km,14-25 km高度内则集中在4.5-5.5 km.      

黄河站和Tromso站亚暴期间热层风场观测结果

中高层大气风场探测对研究大气物理过程具有极为重要的意义，尤其是在极地地区，风场对大气结构的影响更为剧烈.针对亚暴期间中国北极黄河站和日本Tromso站上空OI557.7nm气辉层（低热层）中性风场，利用全天空法布里-珀罗干涉仪（all-sky Fabry-Perot Interferometer，all-sky FPI）探测气辉谱线的多普勒频移，反演气辉层的大气风场信息.结果表明，低热层风场平均水平在100m·s-1左右，热层风场在极地地区更为剧烈，纬度相对较低的Tromso站探测到的风速整体小于同期黄河站上空的风速.结合离子风数据，分析离子拖拽和焦耳加热对中性风的影响过程，发现极光亚暴不仅对低热层风场有增强作用，也有明显的抑制效果，但整体风向都垂直于极光弧变化.      

一种用于测量高层大气风场的新型地基Fabry-Perot干涉仪

地表海拔大约250\,km高度处大气非常稀薄,目前被动光学观测是该层风场探测最有效手段.Fabry-Perot干涉仪(FPI)由于具有较高能量利用率及光谱分辨率等特点,是该层大气最有效的地基风场探测仪器之一.基于采用光路缩束系统及滤光片后置(标准具之后)方法研制的小型化FPI,2014年分别在河北廊坊(39.40°N,116.65°E)和山西岢岚(38.71°N,111.58°E)进行了地基观测试验,将观测数据与反演算法相结合得到高层大气风场数据,并将数据结果与美国大气研究中心两台FPI的风场数据进行了比较研究,在气辉整体辐射较弱的情况下得到岢岚站的风速平均反演偏差为11.8 m·s-1.      

2000年和2001年52°N地区OI5577气辉强度与原子氧浓度峰值的时间变化特征

分析了2000年和2001年期间52°N地区OI5577气辉强度的夜间变化特征和季节变化特征．利用由 OI5577气辉强度反演原子氧浓度峰值的方法反演出原子氧浓度的峰值,分析了峰值的夜间变化特征和季节变化特征．结果表明, OI5577气辉强度的夜间变化特征随季节变化, 2000年春季的夜间强度最大值出现在0000LT 之后,夏季和秋季的出现在0000LT之前,冬季的出现在0000LT,2001年春季和秋季的夜间强度最大值出现在0000LT之前,夏季和冬季的出现在0000LT;OI5577气辉强度在2000年2月份,8月份和10月份出现最大值,在2001年9月份有最大值．就主要特征而言,反演出的原子氧浓度峰值的夜间变化特征和季节变化特征分别与OI5577气辉强度的一致．     

中国上空夜间电离层等离子体泡群演化过程的多设备观测

利用子午工程富克站（19.5°N, 109.1°E）全天空气辉成像仪、VHF雷达、三亚站（18.4°N, 109.6°E）数字测高仪及C/NOFS卫星观测数据，对2014年3月30日中国上空的等离子体泡进行了研究。结果表明，当天夜间观测到一个等离子体泡群，约由9个等离子体泡组成，发生在日落后，一直持续到午夜后。其自西向东运动，南北向最大尺度超过1200 km，东西向绵延超过1400 km，在演化中部分结构融合在一起。等离子体泡被气辉成像仪观测到的同时，数字测高仪及VHF雷达观测到了相应扩展F及羽毛状不规则结构。同时，C/NOFS卫星检测到相应电子密度耗散。这表明，该等离子体泡同时被地基光学观测、无线电探测及C/NOFS卫星观测到。研究结果给出了多仪器同时观测到的等离子体泡群演化过程，丰富了多仪器融合研究电离层不规则体的内容。     

Secular variations of OH nightglow emission and of the OH intensity-weighted temperature induced by gravity–wave forcing in the MLT region

Secular variations of OH airglow (8,3) band and of the intensity-weighted temperature induced by a gravity wave packet at three latitudes in the northern hemisphere in the Mesosphere/Lower Thermosphere region are investigated using a 2-D, time-dependent, fully nonlinear OH chemistry–dynamics model. A net-cycled average survives due to wave transience and dissipation. The integrated OH (8,3) volume emission rates show a 20 percent increase induced by the wave packet. The corresponding intensity-weighted temperature shows an initial increase up to 2 percent then a gradual decrease for the remainder of the simulation time by the same wave packet. These secular variations could be mistaken as long-period or short-period waves in the airglow observations. Therefore, care must be taken when analyzing the data from observations.     

Equatorial planetary waves in the mesosphere observed by airglow periodic oscillations

Planetary scale waves in the equatorial upper mesosphere were studied by measuring the airglow OI557.7 nm, O₂b(0,1) and OH(6,2) emission intensities and OH rotational temperature at São João do Cariri (7.4°S; 36.5°W). From four years of data, 1998–2001, periodic oscillations of the airglow emissions were analyzed using the Lomb–Scargle spectral analysis. An oscillation of 3–4 days was frequently observed, which might be ultra-fast Kelvin waves. No seasonal dependency of the wave activity was found. On some occasions we found a quasi-5-day oscillation with a phase difference between the emissions, suggesting an upward energy flow. This is interpreted as a normal mode Rossby wave.     

Wave perturbations in the MLT at high northern latitudes in winter,observed by two SATI instruments

To investigate the Mesosphere and Lower Thermosphere (MLT) region, several ground-based instruments called SATI (Spectral Airglow Temperature Imager) were designed and built to measure airglow emission and temperature in the upper mesosphere. One SATI instrument was installed at Resolute Bay (74.7°N, 94.9°W) and has monitored the polar MLT region since November, 2001. In October 2007 another SATI instrument was installed at Eureka (80.0°N, 86.3°W) at the Polar Environment Atmospheric Research Laboratory (PEARL) as part of the Canadian Network for the Detection of Atmospheric Change (CANDAC) project. SATI is a spatial scanning Fabry–Perot spectrometer measuring column emission rates for several rotational lines of OH and O₂ airglow at 87 and 94 km height. The rotational temperatures are inferred from the ratios of these lines. The measurements are divided into 12 sectors with an annular field of view. The phase differences between the sectors yield information on the horizontal atmospheric wave direction and wavelength. Horizontal perturbations of 2–8 h period have correlatively been observed and investigated at both locations. Short-periodic oscillations identified as gravity waves with periods between 2 and 8 h propagate in southward and eastward directions, but in opposite directions in some cases. The wave propagation characteristics are often different at the two locations; the relationship with the lower mean wind is considered.     

The Nonlinear Model of the Response of Airglow to Gravity Waves

In this paper, we develope a time-dependent, nonlinear, photochemical-dynamical 2-D model which is composed of 3 models: dynamical gravity wave model, middle atmospheric photochemical model, and airglow layer photochemical model. We use the model to study the effect of the gravity wave propagation on the airglow layer. The comparison between the effects of the different wavelength gravity wave on the airglow emission distributions is made. When the vertical wavelength of the gravity wave is close to or is shorter than the thickness of the airglow layer, the gravity wave can make complex structure of the airglow layer, such as the double and multi-peak structures of the airglow layers. However, the gravity wave that has long vertical wavelength can make large scale perturbation of the airglow emission distribution.     

Thermospheric F-region travelling disturbances detected at low latitude by an OI 630 nm digital imager system

Gravity wave effects in the nocturnal thermospheric F-region domain are seldom detected in the intertropical region by optical (airglow) techniques, especially during geomagnetically quiet times, in part because the low inclination of the magnetic field, as opposed to the case of the mid-latitude region, does not favor significant vertical excursions of ionospheric plasma in response to meridional winds. Such difficulty in detecting gravity wave signatures in the F-region by means of optical techniques tends to increase in the absence of geomagnetic storms because of the lack of strong forcing mechanisms necessary to generate high intensity gravity waves. The purpose of this work is to show that during the quiet day of 9 August 1999, the Terminator may have been a source region of wave-like disturbances in the nocturnal F-region at the low-latitude station Cachoeira Paulista (22°41'S; 45°00W, dip 30°). A digital all-sky OI 630nm imager system located at that station has shown propagating wave-like spatial structures in the airglow intensity near the Terminator. This observation supports a previous study on the evidence of the presence of gravity waves during the post-sunset period at the same location by means of a scanning photometer system (1997, Sobral, J. Atmos. Terr. Phys. 59, 1611–1623). The absence of range-type spread-F as monitored by a local digisonde and the absence of radio wave scintillation as monitored by a local GPS receiver, excludes the hypothesis that the wave-like airglow structures are associated with the occurrence of the ionospheric plasma bubbles. Downwards motion of the iso-density real height contours at 22.0 ms⁻¹ and 33.1 ms⁻¹ are observed. The wave detection by the imager system is reported and discussed here.     

重力波波包在可压大气中的非线性传播

本文采用二维全隐欧拉(FICE)格式对具有高斯分布的重力波波包在等温、可压大气中的非线性传播过程进行数值模拟和分析.数值分析结果表明:尽管存在非线性效应,在整个传播过程中,波动的等相面向下运动,波包和波相关能量向上传输.波相关扰动速度随高度增加指数增长,并且波与平流会发生非线性相互作用,最后导致平均流场增强.这与线性重力波理论完全一致.重力波波包的传播路径与重力波线性射线理论预言非常接近,但平均水平群速度和平均垂直群速度均明显小于线性射线理论给出的结果,可见波动的非线性过程会改变波相关能量的传输速度.模拟结果首次定量地展示出非线性效应对重力波波包传播的影响,表明建立在线性理论框架中的重力波运动学定义的合理性.      

重力波波包在三维非等温大气和水平风场中非线性传播的数值研究

采用全隐欧拉格式（FICE）对重力波波包在三维非等温大气、均匀和剪切风场中的非线性传播进行了数值模拟，给出了重力波波包三维非线性传播的全过程，分析了重力波的传播特性及背景温度场、风场对重力波传播的影响。结果表明：波包扰动速度振幅的增长比在WKB条件下振幅的增长要慢；波包非线性传播的路径、能量传输速度不同于WKB近似下的结果，非线性效应导致了重力波的传播特性的改变；温度场的非均匀性会改变重力波传播的路径和速度；剪切风场使扰动速度振幅的增加变得缓慢，使垂直波长减小。     

双变量波状扰动激发重力波波包的数值研究

采用谱配置方法对双变量波状扰动激发重力波的过程及其能量传播和转换特性进行数值研究．模拟结果表明，当初始给定的两个变量的波状扰动的相对振幅和相位严格满足重力波的偏振关系时，只有水平风场扰动(u′)与温度扰动(7′)的共同作用才能抑制能量向下传输．通常情况下，两个变量的波状扰动都会激发出两文传播方向相反的重力波波包，这两支波包的相对能量明显取决于两个波状扰动之间的相对振幅关系．当两个扰动之间的相对振幅满足特定条件时，向下传播的能量几乎为零，只会有一支向上传播的重力波波包被激发．进一步的数值分析则表明，各种情况下两个变量的波状扰动所激发的重力波波包的能量传播路径和速度基本相同；与单变量波状扰动激发重力波波包的过程相比，能量传播路径几乎完全一致，扰动转化为波动的特征时间也基本相同，但能量转换效率更高．     

Energy transfer by gravity wave dissipation

This paper reviews the subject of the dissipation of internal gravity waves in the thermosphere and shows how this is related to propagation. Differences of dissipation and heating rates in quiet and disturbed atmospheres are discussed, and the ranges of waves for different source heights in these atmospheres are calculated. Despite heavy damping of the waves, they may explain T.I.D.'s and related airglow observations in middle and low latitudes.