中国廊坊中间层和低热层大气平均风观测模拟

利用中国廊坊站（39.4°N,116.7°E）流星雷达在2012年4月1日至2013年3月31日的水平风场观测数据,分析廊坊上空80~100km的中间层与低热层（Mesosphere and Lower Thermosphere,MLT）大气平均纬向风和经向风的季节变化特征.结果表明平均纬向风和经向风都表现出明显的季节变化特征.平均纬向风在冬季MLT盛行西风,极大值位于中间层顶,随高度增加西风减弱;在夏季中间层为东风,低热层为强西风,风向转换高度约为82km.平均经向风在冬季以南风为主,在夏季盛行北风.纬向风和经向风在春秋两季主要表现为过渡阶段.流星雷达观测结果与WACCM4模式和HWM93模式模拟的气候变化特点基本一致,但WACCM4模式纬向风和经向风风速偏大,而HWM93模式纬向风和经向风风速偏小.      

中国地区20──80km高空风的一些特征

利用Nimbus-7卫星1979-1981年的平流层和中间层大气温度探测数据(SAMS)和热成风原理,计算了高空风场,得到中国上空20──80km高度范围风场的一些特征。结果表明,用地转一热成风公式从卫星温度探测数据计算的高空风与当日中国气象火箭探测的高空风基本一致,说明利用卫星温度数据是获得中国20-80k高空风气候特征的一种有效的方法;从计算出的风场看,中国上空20──80km的纬向风与COSPAR国际参考大气CIRA-1986的纬圈平均纬向风有显着差别,文中还给出了经向风的分布和风场的变化情况。      

北纬30°N中间层和低热层大气平均风中频雷达观测

利用武汉(30.5°N,114.4°W)中频雷达在2001年1月1日至3月18日、2002年2月5日至3月18日、2002年10月18日至12月31日期间,日本Yamagawa(31.2°N,130.6°W)中频雷达在1997年1月1日至10月17日期间的数据,分析北纬30°N地区上空60-98km高度的中间层、低热层大气平均风的变化规律,结果表明平均纬向风和经向风都具有明显的季节变化.平均纬向风在冬季基本为西风,随高度增加,西风减弱,甚至在上部会出现微弱的东风;夏季中间层表现为强烈的东风,低热层则为西风,风向转换高度在80km附近;春季和秋季为转换季节,在春季出现舌状东风结构.80km附近的平均经向风场在冬季以南风为主,在夏季则以北风为主.不同年份的平均风场存在年际变化性,但其气候变化特点非常相似.中频雷达观测结果与HWM93模式结果的气候变化特点符合很好,与其他纬度的平均纬向风气候变化特点基本类似.     

TIMED卫星探测的全球大气温度分布及其与经验模式的比较

利用TIMED卫星遥感探测的全球温度分布与NRLMSISE-00大气经验模式进行了对比研究.研究表明,在中间层下部以下的高度范围内,经验模式与卫星探测的大气温度分布有很好的一致性.但是比较发现,在中层顶区域,经验模式的计算结果与实测结果有较大的差异.卫星探测表明,在春分季节的低纬地区中层顶区存在稳定的逆温层,但是经验模式不能给出低纬地区春分季节中间层逆温层的分布特征.卫星观测表明在全球范围内中层顶有两个非常不同的高度,一个处于100km附近,另一个处于85km附近,但是经验模式不能给出这一中层顶高度的分布特征.同时在低热层,经验模式计算的温度分布与卫星遥感的探测结果有很大的差异.      

中高层大气风场对地磁活动的响应特征

统计研究漠河、北京、武汉流星雷达观测到的2012-2018年80～100 km高度的风场数据，比较在地磁平静期(Kp≤2)和地磁扰动期(Kp≥4)的日平均风场数据，得到在地磁活动期风场的变化特征。研究结果表明，在地磁扰动时风场变化具有季节差异和纬度差异。地磁扰动期间，纬向风在较高纬度地区倾向于中间层西风增强，低热层东风增强，纬度较低地区倾向于东风增强。春季，地磁活动对纬向风的影响没有纬度差异，在夏冬季随着纬度的降低中间层东风增强明显。地磁活动对经向风的影响具有季节差异，对春冬季节的影响强于夏秋季节。研究表明，地磁活动对纬向风的影响可达9 m·s^–1左右，对经向风的影响可达5 m·s^–1左右。地磁活动对中性大气风场的影响可达80 km。     

中国上空平流层准零风层的特征分析

利用ECMWF提供的ERA-40再分析风场资料首次分析了中国上空平流层准零风层的特点及其随季节和地理位置的变化特征.结果表明,准零风层一般处于18～25 km高度范围内,零风线所在的高度随时间和地理位置的不同稍有变化.根据准零风层随纬度的变化特征,中国上空可以分成三个区域:低纬地区(5°N～20°N)、中低纬过渡区域(20°N～32.5°N)和中高纬地区(32.5°N～55°N).低纬地区一般在冬季和初春有准零风层结构存在;中高纬地区一般在春末和夏季存在准零风层结构;而中低纬过渡区域是否有准零风层结构存在还与准两年震荡(QBO)有关,在QBO东风相位时,过渡区域呈现的特性偏向于中纬特性,在QBO西风相位时,过渡区域呈现的特性偏向于低纬特性.准零风层随经度变化非常小,零风线所在高度随经度的变化幅度一般不超过2 km,过渡区域的变化幅度相对大些.      

用织女一号火箭在海南站探测的高空风和风切变

本文介绍了织女一号(ZN-l)火箭测风原理,数据处理方法和两次测风结果.结果指出,在我国低纬地区中层大气中存在非常明显的风切变和相当强的重力波扰动,测风数据与COSPAR国际参考大气CIRA1986及国际标准化组织航空用参考大气ISO5878-1982／ADD.1-1983存在明显差别.      

极区夏季中间层半日潮汐的VHF雷达观测

采用德国SOUSYVHF雷达观测数据,研究了极区夏季中间层半日潮汐的结构和变化特征.纬向和经向风的动态Lomb-Scargle谱表明,半日潮是中间层高度上占支配地位的波动,其谱峰对应的频率一般与1/12c·h-1有偏离,说明它们经常处在被扰动状态.稳定的半日潮振幅随高度增加而迅速增长,在87.9km高度附近达到饱和;经向分量的相位一般比纬向分量的相位超前π/4-π/2,从而水平扰动速度矢量端点随时间变化的轨迹显示出顺时针方向旋转的特征.半日潮汐特征参量在纬向和经向风中随时间的变化在基本趋势一致的基础上显示出一定程度的各向异性.      

基于MST雷达数据的中纬对流层和低平流层大气行星波研究

通过分析中国河北香河站MST (Mesosphere-Stratosphere-Troposphere)雷达 2012-2014年的水平风场数据, 研究了北半球中纬地区对流层和低平流层 (Troposphere and Lower Stratosphere, TLS)区域大气行星波的特性. 谱分 析发现, 在这一区域准16天波和准10天波占据主导地位, 准16天波更为显著. 在 对流层区域, 行星波具有丰富的频谱成分, 活动具有间断性, 持续时间一般不 超过三个月, 并没有明显的季节性变化特征, 其中纬向分量的振幅大于经向分量. 在 平流层区域(高度17km以上), 行星波一般出现在冬季, 并且主要在纬向分量中. 通常平流层区域的振幅要小于对流层区域. 结合MERRA再分析资料分 析了强行星波传播特性, 结果表明: 2014年2-3月纬向分量中的准16天波垂 直向上传播, 垂直波长约为64km, 纬圈波数约为2, 纬向传播方向自西向东, 水平波长约为15324.7km, 对应的相速度为11.1m·s-1 (向东为正); 2014年5月纬向分量中的准10天波在10~18km高度范围内向下传播, 垂直波长约为50km, 纬圈波数约为1, 传播方向自西向东, 水平波长约为 30649.4km, 对应相速为35.5m·s-1.      

基于钠激光雷达观测数据的中间层顶大气温度分布特性研究

作为中间层和热层的边界层,中间层顶存在多种能量交换方式,是大气能量耦合的重要区域。本文利用部署于中国科学院廊坊临近空间大气探测站的钠荧光多普勒激光雷达2013年的观测数据,研究了廊坊上空中间层顶区域大气温度的年度和季节分布特性,并分析了影响温度分布的多种因素。年平均温度廓线图显示,中间层顶位于约97.5 km高度处,温度约191.2 K。受放热化学反应的影响,年平均温度廓线91 km高度处出现了一个198 K的相对温度高点。中间层顶区域大气温度的季节分布受太阳辐射和大气动力学因素综合影响,夏季在大气动力学影响下,中间层顶高度较低,位于88 km高度处,温度也较低,约177 K;冬季太阳辐射起主导作用,中间层顶位于99 km高度处,温度为181 K。通过拟合月平均温度分析了中间层顶区域大气温度年变化和半年变化的振幅和相位特征。结果显示,中间层顶区域上部温度分布主要受太阳辐射的影响;在中间层顶区域下部,大气波动主导了温度分布。      

Comparisons of winds at (44°S, 173°E), 65–110km,with CIRA 72

In the 95km height region of the atmosphere, ground-based techniques made an important contribution to the CIRA 72 [1] wind model. Recent wind measurements from a partial reflection experiment at 44S covering one and a half years are presented and compared with CIRA 72. The zonal wind component compares favourably, although the measured values are more easterly above 80km in autumn and winter; a feature of the autumn winds is a temporary easterly reversal above 90km. Winter mesospheric winds can be very disturbed. The summer mesosphere easterly maximum appears earlier in the season and at a higher altitude than the model. A much poorer comparison is shown between the measured meridional wind component and the 1969 model of Groves [2].     

Horizontal winds in the mesosphere at high latitudes

A total of 146 meteorological rocket flights applying the ‘falling sphere’ technique are used to obtain horizontal winds in the mesosphere at polar latitudes, namely at the Andøya Rocket Range (69°N, 125 flights), at Spitsbergen (78°N, 10 flights), and at Rothera (68°S, 11 January flights only). Nearly all flights took place around noon or midnight, i.e., in the same phase of the semidiurnal tide. Meridional winds at 69°N show a clear diurnal tidal variation which is not observed in the zonal winds. The zonal wind climatology shows a transition from summer to winter conditions with the zero wind line propagating upward from 40 km (end of August) to 80 km (end of September). Zonal winds are smaller at Spitsbergen compared to Andøya which is in line with a common angular velocity at both stations. Meridional winds at noon are of similar magnitude at all three stations and are directed towards the north and south pole, respectively. Horizontal and meridional winds generally agree with empirical models, except for the zonal winds at Antarctica which are similar to the NH, whereas there is a significant SH/NH difference in CIRA-1986.     

Comparisons between primrose lake (54°N, 110°W) ROCOB winds (20–60 km) and Saskatoon (52°N, 107°W) M. F. radar winds (60–110 km): 1978–1982

The development of the new CIRA will require the combination of winds from many sources, e.g. rockets (ROCOB) up to ～60 km, and radar winds ～60–110 km. Difficulties are that such rocket data have larger errors at 60–65 km, and tidal effects may become significant. Radar data for 60–80 km may also have tidal contamination, due to ? 16h of data per day: from 80–110 km tidal corrections are usually reliable.Comparisons are made between the unique Saskatoon MF radar set, which is continuous from mid 1978–1983, and the ROCOB data from Primrose Lake, which is only 340 km northwest. While the agreement is satisfactory, special care is required when matching the two regions: particular problems are the low rocket sampling rate, and the unexpectedly large amplitude of the diurnal tide. Important differences from the zonal winds of CIRA-72 emerge, especially in winter months. Meridional cross-sections differ from previous data models in the extent of the summer equatorward flow.     

Semi-empirical model of middle atmosphere wind from the ground to the lower thermosphere

During recent years, special attention has been paid to understanding the background circulation of the middle atmosphere. Particularly in the mesosphere/lower thermosphere (MLT) region, this has involved including data from a range of new radar measurements. It has also involved the comparison of existing empirical middle atmosphere wind models, such as CIRA-86 and HWM-93 to the new data. This has led to the construction of empirical models of MLT winds such as the Global Empirical Wind Model (GEWM). Further investigations are aimed at the construction of new empirical and semi-empirical wind models of the entire middle atmosphere including these new experimental results. The results of a new wind climatology (0–100 km) are presented here, based upon the GEWM, a reanalysis of stratospheric data, and a numerical model which is used to fill the gap between data from the stratospheric and MLT regions.     

Comparison of mesopause region meteor radar winds,medium frequency radar winds and low frequency drifts over Germany

During 2004 and 2005 measurements of mesospheric/lower thermospheric (80–100 km) winds have been carried out in Germany using three different ground-based systems, namely a meteor radar (36.2 MHz) at the Collm Observatory (51.3°N, 13°E), a MF radar (3.18 MHz) at Juliusruh (54.6°N, 13.4°E) and the LF D1 measurements using a transmitter (177 kHz) at Zehlendorf near Berlin and receivers at Collm with the reflection point at 52.1°N, 13.2°E. This provides the possibility of comparing the results of different radar systems in nearly the same measuring volume. Meteor radar winds are generally stronger than the winds observed by MF and especially by LF radars. This difference is small near 80 km but increases with height. The difference between meteor radar and medium frequency radar winds is larger during winter than during summer, which might indicate an indirect influence of gravity waves on spaced antenna measurements.     

Zonal mean temperature, pressure, zonal wind and geopotential height as functions of latitude

The new zonal mean COSPAR International Reference Atmosphere (CIRA-86) of temperature, zonal wind, and geopotential/geometric height is presented. This data can be used as a function of altitude or pressure and has nearly pole-to-pole coverage (80°S-80°N) extending from the ground to approximately 120 km. Data sources and methods of computation are described; in general, hydrostatic and thermal wind balance are maintained at all levels and latitudes. As shown by a series of cross sectional plots, the new CIRA accurately reproduces most of the characteristic features of the atmosphere such as the equatorial wind and the general structure of the tropopause, stratopause, and mesopause.     

A simple model for the interhemispheric coupling of the middle atmosphere circulation

The interhemispheric coupling of the middle atmosphere general circulation is characterized by a global anomaly pattern of the zonal-mean temperature. This pattern reflects an anomalous stratospheric and mesospheric residual circulation, in which a weaker (stronger) stratospheric winter circulation is linked to an upward (downward) shift of its upper mesospheric branch reaching from the summer to the winter pole. This phenomenon is robust in observational data and several middle atmosphere general circulation models. In the present study, the recently proposed mechanism of the interhemispheric coupling is unequivocally proven within the framework of a zonally symmetric model that excludes any additional effects due to resolved waves and non-zonally propagating gravity waves. Two simulations are conducted that differ in the strength of the polar vortex. A weaker polar vortex results in a downward shift of the winter mesospheric gravity wave drag. This leads to changes also in the summer upper mesosphere via a feedback solely between gravity wave breaking and the zonal-mean state. The accompanying temperature anomaly reproduces the pattern of the interhemispheric coupling.     

Mean winds of the mesosphere and lower thermosphere (60–110 km): A global distribution from radar systems (MF,Meteor, VHF)

During the last decade a large number of radars (～12) have been developed, which have produced substantial quantities of tidally-corrected mean winds data. The distribution of the radars is not global, but many areas are well covered: the Americas with Poker Flat (65°N), Saskatoon (52°N), Durham (43°N), Atlanta (34°N), Puerto Rico (18°N); Europe with Kiruna (68°), Garchy (47°N) and Monpazier (44°N); and Oceania with Christchurch (44°S), Adelaide (35°S), Townsville (20°S), and Kyoto (35°N). Zonal and meridional wind height-time cross-sections from $\text{60}\text{80}$ km (MF/Meteor Radar) to ～110 km have been prepared for the last 5–6 years. They are compared with cross-sections from CIRA-72 for zonal winds, and Groves (1969) for meridional winds.It is shown that while CIRA-72 is still a useful model for many purposes, significant differences exist between it and the new radar data. The latter demonstrate important seasonal, latitudinal, longitudinal and hemispheric variations. The new meridional cross-sections are of great value. The common features with Groves (1969) are the equatorward cells in summer near 85 km; however their strength (～10 ms^?1) and size are less. Systematic and somewhat different variations emerge at higher (?52°N) and middle (35–44°) latitudes.