损耗热层中大气声重波的扰动速度、能流和传播矢量

本文从包含损耗的流体力学方程组出发,研究了中尺度声重波在热层中的运动学特性.文中引入一个偏振因子描述扰动速度矢端的轨迹——偏振椭圆.讨论了波扰动速度与波能流的关系,结果表明波能流仰角的正切等于偏振因子的实部.根据这一结果,建立了偏振椭圆与波能流的几何联系.为表明损耗对声重波运动特性的影响,文中进行了数值计算.分析指出,在240km以上的高度,损耗对声重波的运动学特性产生很大的影响:1.损耗使波能流向水平方向靠近,波出现类似导制传播下的行为.2.损耗减小了波传播矢量与波能流之间的夹角,因此削弱了波的各向异性.3.损耗使偏振椭圆的形状由狭长变“圆”,Boussinesq近似不再合理.随高度增加损耗加强,损耗情况下声重波的运动特性与无耗场合差异甚大.     

地形对正压大气Rossby波非线性相互作用的影响

本文采用弱非线性近似，推导出地形和Ｅｋｍａｎ摩擦共同作用下连续谱正压Ｒｏｓｓｂｙ波的非线性时空演化方程．根据这组方程，我们研究了窄角谱Ｒｏｓｓｂｙ波包的波波相互作用问题，当一个大振幅Ｒｏｓｓｂｙ波包通过大气传播时，如果它的振幅超过某个阈值，非线性相互作用会使一个尺度比它大的Ｒｏｓｓｂｙ波包和一个尺度比它小的Ｒｏｓｓｂｙ波包的振幅随时间指数增长，这两个次级波的本征频率会发生改变，Ｅｋｍａｎ摩擦、频率不匹配、地形坡度以及波包的空间演变共同决定了主波振幅的阈值及次级波本征频率的改变量．     

大气激光雷达光电转换单元及其自检系统

基于双波长激光雷达的光电转换单元及其核心部件光电倍增管（PMT）的基本原理，对使光电倍增管工作的分压电路进行了剖析和改造，完成了激光雷达魇始回波从信号到电信号的转换，设计并实现了激光雷达光电转换自检系统，模拟了大气回波光子计数信号并产生相关控制信号，成功地解决了激光雷达信号处理部分调试困难的问题。     

1m反射式卡塞格伦系统的调试

介绍了高空大气探测激光雷达的接收物镜(卡塞格伦物镜)的光路及调试方法。给出30-60km的Rayleigh回波和80-110km钠层回波信号，与原来的离轴抛物物镜的回波信号相比，具有更高的Rayleigh回波高度、更高的信号值与信噪比。     

Resonant nonlinear interactions between atmospheric waves in the polar summer mesopause region

Data obtained from the mobile SOUSY VHF radar at And(ya/Norway in summer 1987 have been used to study the nonlinear interactions between planetary waves, tides and gravity waves in the polar mesosphere, and the instability of background atmosphere above the mesopause. It is observed that 35-h planetary wave, diurnal, semidiurnal and terdiurnal tides are the prominent perturbations in the Lomb-Scargle spectra of the zonal wind component. By inspecting the frequency combinations, several triads are identified. By bispectral analysis it is shown that most bispectral peaks stand for quadratic coupling between tidal harmonics or between tide and planetary or gravity wave, and the height dependence of bispectral peaks reflects the variation of wave-wave interactions. Above the mesopause, the occurrence heights of the maximum L-S power spectral peaks corresponding to the prominent wave components tend to increase with their frequencies. This may result from the process in which two low frequency waves interact to generate a high frequency wave. Intensities of the planetary wave and tides increase gradually, arrive at their maxima, and then decay quickly in turn with increasing height. This kind of scene correlates with a "chain" of wave-wave resonant interactions that shifts with height from lower frequency segment to higher frequency segment. By instability analysis, it is observed that above the mesopause, the Richardson number becomes smaller and smaller with height, implying that the turbulent motion grows stronger and stronger and accordingly the background atmosphere more and more instable. It is suggested that the wave-wave sum resonant interaction and the wave dissipation due to instability are two dominant dynamical processes that occur in the mesopause region. The former invokes the energy transfer from lower frequency waves to higher frequency waves. The latter results in the heating of the atmosphere and accelerating of the background flow.     

The influence of topography on the nonlinear interaction of Rossby waves in the barotropic atmosphere

ＴＨＥＩＮＦＬＵＥＮＣＥＯＦＴＯＰＯＧＲＡＰＨＹＯＮＴＨＥＮＯＮＬＩＮＥＡＲＩＮＴＥＲＡＣＴＩＯＮＯＦＲＯＳＳＢＹＷＡＶＥＳｉＮＴＨＥＢＡＲＯＴＲＯＰＩＣＡＴＭＯＳＰＨＥＲＥＸｉｏｎｇＪｉａｎ－ｇａｎｇ（熊建刚）ＹｉＦａｎ（易帆）ＬｉＪｕｎ（李钧）（...     

剪切流动中短周期声重波的产生与发展

本文根据可压缩情况下的流体力学方程组,采用局域近似理论,建立了剪切流动中扰动的发展方程。本文还导出了剪切流动中声重波的色散关系,给出了参数空间中稳定与不稳定的分界图象,文中还给出了不稳定波增长率和振荡频率随切变强度和波长的分布,发现剪切不稳定性倾向于激发短周期的波动,其本征振荡周期的范围是1—6min按照色散关系和扰动的发展方程,本文讨论了白噪声形式的初始扰动在剪切流动中的演变过程。