【作者】 肖存英；

【导师】 胡雄；

【作者基本信息】 中国科学院研究生院（空间科学与应用研究中心） ， 空间物理学， 2009， 博士

【摘要】 临近空间大气是指20-120km的大气,是地球中高层大气的重要组成部分。临近空间大气存在着与太阳活动影响的日-地关系和低层气象变化相关的复杂耦合作用,与人类的生存和发展密切相关,对航天活动具有重要的影响,因此,对临近空间大气特性和内在机制的研究一直是各国科学家关注的领域。尤其是在近几年,临近空间的开发利用对临近空间大气的探测与研究提出了迫切的需求。在此背景下,本文选题临近空间大气动力学前沿研究,对临近空间大气进行了若干特性的分析及模式研究,主要研究内容可以概括为以下七个方面:(1)利用NCAR的二维物理模式(SOCRATES)模拟研究了临近空间大气温度和风场的气候变化特征,将模拟结果与中频雷达风场观测结果和TIMED/SABER卫星温度观测结果进行了比较,结果相互吻合。采用资料分析和模拟研究相结合的方法,利用武汉和日本中频雷达资料和SOCRATES模式,分析了中间层和低热层(MLT)大气的风场结构特性,首次利用模式模拟结果解释了北纬30oN中频雷达风场的季节变化特征,揭示了大气重力波在MLT大气结构中的重要性。(2)利用新的COSMIC GPS无线电掩星观测温度数据计算了大气重力波的位能,分析得到了低平流层大气重力波活动的全球分布特征,揭示了重力波波源和背景风场的影响,以及大气行星波的调制作用。(3)利用TIMED/SABER的温度数据,通过仿真模拟实验首次定量地分析了由于数据地方时覆盖不全造成的信号混淆对提取大气定常行星波的影响,并首次获得了20-135km全球大气定常行星波的活动特征,尤其是100-135km低热层大气行星波活动特征,发现在上中间层及低热层存在较强的大气行星波活动,分析结果对该领域的研究具有重要的意义。(4)利用ERA-40再分析风场资料,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。结果指出,准零风层一般处于18~25km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(5oN~20oN),中低纬过渡区域(20oN~32.5oN)、中高纬地区(32.5oN~55oN)。(5)分析和比较了利用卫星温度资料计算水平风场的方法,包括地转风、梯度风和平衡风的计算方法。以DAAC提供的MLS/UARS 1992年12月份的大气温度数据为例,计算了20-55km高度范围的地转风、梯度风和平衡风,并与ERA-40再分析风场资料作了对比和分析。结果显示,计算出的风场与再分析资料的特征和规律基本一致,由此表明,利用卫星温度观测资料通过理论公式进行数值计算是获取高空风特征的一种非常有效的方法,是弥补20-60km直接观测资料少的一种有效的途径。此外,利用平衡风场的计算结果,文中首次定量的计算了平衡方程中各项的大小和比值,分析了各项的贡献和相对重要性。(6)利用COSMIC资料分析得到了2007/2008年平流层爆发性增温(SSW)期间10-60km大气的变化特征,揭示了上平流层和下中间层大气(USLM)在SSW过程中西风减弱或反转、温度降低的特性,并通过波流相互作用理论从动力学方面对大气的变化特性进行了解释,结果表明, 2007/2008年SSW的发生可能是由底部超过某个临界值的行星波向上传播,与平流层与中间层的平均流相互作用引起的。此外,文中还通过热力学方程和连续性方程计算和分析了剩余环流在SSW期间的变化特性,结果显示,剩余环流在SSW期间环流圈的方向会发生反转。(7)利用TIMED/SABER 7年的观测数据建立了临近空间20-90km的大气月平均气候模式,参量包括:温度、压强、密度和水平风场。之后,利用该气候模式分析了北京、武汉、拉萨和海南临近空间大气环境的变化特性,并尝试了人工神经网络在建立中层大气气候模式中的应用,成功地构建了一个三层的BPNN神经网络模型,反映了2007年2月份20-70km高度范围内的月平均温度结构特性,可为将来临近空间大气的建模工作提供参考。更多还原

【Abstract】 Near space atmosphere refers to the atmosphere in the altitude range from 20km to 120km,the important part of the earth’s middle and upper atmosphere. Many complex couplings related to the Sun-Earth connection under the effects of the solar activity and to the meteorologic variability fill the near space atmosphere, which is highly associated with living environments of human beings, and has significant influences on the spaceflight activities. Therefore, scientists all over the world have paid much attention to the studies of the atmospheric characteristics and their intrinsic mechanisms. Especially in the recent years, the rapid development and application of the near space techniques push the requirements of further explorations and researches of the near space atmosphere. Under this background, some front aspects of atmospheric dynamics in near space are selected for further investigation in this thesis. The works in the thesis are mainly focused on the analysis of the characteristics of the near space atmospheric dynamics and its model studies, which can be summarized as the following seven aspects:(1) Simulations are taken by the NCAR’s two dimensional physical model (SOCRATES) to study the climatic characteristics of the atmospheric temperature and wind fields in near space. Those simulation results are compared with the MF radar and the TIMED/SABER observations, which shows consistent features. With the method of combining the observations and the model simulations, the observations of Wuhan and Japanese MF radar and the SOCRATES model are used to analyze the characteristics of the wind fields in the mesosphere and lower thermosphere (MLT). With the results of the simulations, the features of wind seasonal variations at 30oN observed by MF radar are firstly interpreted. Results suggest the importance of the atmospheric gravity waves in determining the MLT wind structures.(2) With the new temperature profiles of COSMIC GPS radio occultation, the potential energies of atmospheric gravity waves are calculated, obtaining the global morphology of stratospheric gravity wave activity. The influences of the origins and the background winds and the modulation of the planetary waves on the gravity wave activity are discussed in details.(3) The temperature measurements from SABER instrument on board of TIMED satellite are used to study the temperature stationary planetary waves (SPWs). Through simulation, the amplitudes of the SPW parameters leaked from the nonmigrating tides due to the non-uniform sampling of the data in the LST domain are first quantitatively calculated. The global temperature SPWs extending from 20-135km by TIMED/SABER are firstly obtained. The SPWs in the upper mesosphere and lower thermosphere (UMLT) are large. These results are significant, especially for the results between 100 and 135km(4) The characteristics of the stratospheric quasi-zero wind layer and its seasonal and geographic variation features over China are obtained by using the ERA-40 reanalyzed wind data. Results show that quasi-zero wind layer generally exists at the height range of 18-25km and some variation of the height of the zero wind line would happen when the time or location change. According to the latitudinal variation of the quasi-zero wind layer, the atmosphere over China could be divided into three parts to discuss its features: low-latitude area (5oN-20oN), transition area (20oN-32.5oN), middle and high-latitude area (32.5oN-55oN).(5) Several methods of deriving horizontal wind fields from satellite temperature data are analyzed and compared in this paper, including the calculation methods of geostrophic wind, gradient wind and balance wind. Taking the temperature data of MLS/UARS in December, 1992 offered by DAAC for example, geostrophic wind, gradient wind and balance wind fields at the altitude range of 20-55km are inferred and compared with ERA-40 reanalyzed wind fields. Results show that, the characteristics of calculated winds are similar with that of the reanalyzed data, indicating that deriving wind fields from the satellite temperature data through theoretical equations is an effective way to supply the gap of lack of wind observations in the 20-60km. Moreover, values and ratios of the terms in balance equations are firstly calculated in this study, and the contribution and relative importance are also analyzed. (6) The observations of COSMIC are used to analyze the variability of the atompshere between 10 and 60km during the sudden stratospheric warming (SSW) in 2007/2008. Results show that the westerly wind is weakened or reversed, and the temperature is cooled during the SSW in the upper stratosphere and lower mesosphere (USLM). Through the wave-mean low interactions, the features are interpreted from the dynamic aspects. Results suggest that the occurrence of the SSW in 2007/2008 may be ralated to the planetary waves, which exceed the critical values, and propagate upward, interact with the mean flow in the upper atostratosphere. Furthermore, through the thermodynamic and continuous equations, the residual circulations are calculated and analyzed, with the results that during SSW, the circulation circles of the residual circulations are reversed.(7) With the 7-year TIMED/SABER observations, a monthly-mean climate model has been developed. The parameters include temperature, pressure, density and horizontal winds. As an example of the application of this model, the atmospheric environments over Beijing, Wuhan, Lasa and Hainan are analyzed. In addition, Artificial neural network (ANN) is used to seek the middle atmosphere modeling with the abundant TIMED/SABER limb observed temperature profiles. A three-layer feed-forward network based on the back-propagation (BP) algorithm has been successfully constructed with the aim of reflecting the monthly mean temperature structure between 20 and 70km in 2007 February. These modeling experiments can provide some reference for future modeling.更多还原