A study of the environmental influence on the amplitude of lee waves   总被引：1，自引：0，他引：1  

臧增亮  张铭 《大气科学进展》2008,25(3):474-480

A three-layer theoretical model is used to calculate the lee wave of a real example occurring over Blue Ridge in Pittsburgh, in which the maximum vertical velocity is 0.11 m s^-1. Based on this, the influence of changes in the thickness and values of the Scorer parameter in each layer are analyzed. It is shown that the influence of each layer parameters on the lee-wave amplitude is different, and the amplitude is more sensitive to the changes in the lower layer. Since the environment changes can affect the Scorer parameter profile, the influence of the environment on the amplitude is studied. The results show that the amplitude will decrease in the daytime because of solar heating, and increase at night because of radiational cooling, according to observational data. The case is also simulated by the Advanced Regional Prediction System （ARPS） model. The simulated amplitude is 0.089 m s^-1, which is close to the calculated result. Numerical sensitivity experiments are performed to test the former calculated experiments. The simulated results are consistent with the analytically calculated results.  相似文献   

ENSO amplitude change in observation and coupled models     

张琼  关月  杨海军 《大气科学进展》2008,25(3):361-366

Observations show that the tropical E1 Nifio-Southern Oscillation （ENSO） variability, after removing both the long term trend and decadal change of the background climate, has been enhanced by as much as 60% during the past 50 years. This shift in ENSO amplitude can be related to mean state changes in global climate. Past global warming has caused a weakening of the Walker circulation over the equatorial Indo-Pacific oceans, as well as a weakening of the trade winds and a reduction in the equatorial upwelling. These changes in tropical climatology play as stabilizing factors of the tropical coupling system. However, the shallower and strengthening thermocline in the equatorial Pacific increases the SST sensitivity to thermocline and wind stress variabilities and tend to destabilize the tropical coupling system. Observations suggest that the destabilizing factors, such as the strengthening thermocline, may have overwhelmed the stabilizing effects of the atmosphere, and played a deterministic role in the enhanced ENSO variability, at least during the past half century. This is different from the recent assessment of IPCC-AR4 coupled models.  相似文献   

一种简易快速的时域地震波衰减补偿算法     

张瑾  冯晅  刘财  赵旭  张营  刘海燕  王乔 《吉林大学学报(地球科学版)》2010,(Z1)

针对地震波的能量随着传播时间的增加而递减,提出了一种时间补偿方法。通过调试与传播时间有关的两个可调参数进行地震波振幅补偿。模型试验证实了该方法可以有效地补偿能量的损失,而且在地层中地震波振幅衰减与品质因子Q值有关时,其中的一个可调参数可以用另一个可调参数和Q值来表示。也就是说,本文方法同样是一种反Q滤波方法。  相似文献   

三维地震技术在探测煤矿腔状采空区中的应用   总被引：1，自引：0，他引：1  

段建华  杨文强  倪新辉 《中国煤炭地质》2010,(8):21-24,38

采用三维地震勘探方法对采空区进行勘探,虽积累了大量的经验,但在实际应用中,解释误差依然存在,尤其是煤层顶板悬空,并在一定范围内呈"腔状"类型的采空区,会出现较高的"漏检率"。为此根据实际地层序列设计了地质模型,对采空区的地震反射波场特征进行了研究。将腔状采空区充气、充水时的正演地震剖面,与煤层开采前正常地层波场响应特征进行对比发现,煤层开采后将会产生比正常波场能量更强的反射波组。另外根据腔状采空区充水和充气反射波最大振幅及反射波频谱对比结果,还发现充气时产生的反射波能量比充水时产生的反射波能量强;充气时产生的反射波频率比充水时产生的反射波频率要低。山西左权佳瑞煤业有限公司的应用实例佐证了三维地震勘探技术探测腔状采空区的有效性。  相似文献   

An Approximate Method for Calculation of Fluid Force and Response of A Circular Cylinder at Lock-in     

王艺 《中国海洋工程》2008,22(3):371-384

In this paper, equations calculating lift force of a rigid circular cylinder at lock-in in uniform flow are deduced in detail. Besides, equations calculating the lift force on a long flexible circular cylinder at lock-in are deduced based on mode analysis of a multi-degree freedom system. The simplified forms of these equations are also given. Furthemore, an approximate method to predict the forces and response of rigid circular cylinders and long flexible circular cylinders at lock-in is introduced in the case of low mass-damping ratio. A method to eliminate one deficiency of these equations is introduced. Comparison with experimental results shows the effectiveness of this approximate method.  相似文献   

鄂尔多斯黄土塬直测线二维地震资料处理攻关试验     

任和爱  李刚 《海洋地质前沿》2008,24(7)

针对鄂尔多斯盆地南部黄土塬区复杂地表条件下的直测线二维地震资料进行了处理攻关试验,通过近地表模型静校正、折射波静校正和层析静校正等方法的对比试验,提出了更适应本地区的静校正方法。并且通过振幅补偿、叠前去噪等技术方法改善了资料品质,提高了资料的信噪比和分辨率,可为进一步落实和发现局部构造及勘探开发部署提供重要的依据。  相似文献   

乌鲁木齐附近地区小爆破识别判据的研究   总被引：1，自引：3，他引：1  

杨成荣  王桂岭  敖雪明 《内陆地震》2001,15(1):30-38

采用新疆乌鲁木齐地区多个地震台的位移仪及速度仪记录，探讨了人工小爆破记录与天然地震记录的差异及其识别判据。结果发现，爆破记录与地震记录在震相、P波垂直向初动符号分布、振幅衰减、振幅比As^-/Ap^-等方面具有不同的特征，据此我们制定出了识别爆破的单项判据和综合判据。  相似文献   

定向裂缝对地震波速度和振幅影响的比较—实验结果分析   总被引：30，自引：2，他引：30  

贺振华  李亚林  张帆  黄德济 《物探化探计算技术》2001,23(1):1-5

利用垂直定向裂缝模型和MTS岩石物性测试系统，测试了不同材料和不同状态裂缝模型的地震特征响应。对特征响应进行分析和比较后发现，虽然波的传播速度，振幅，吸收衰减，主频均可用来检测裂缝的特征参数，但是裂缝变化对振幅的影响大于对速度的影响。因此，利用地震波的振幅、衰减等属性参数检测裂缝特征比利用速度参数更有效。  相似文献   

尾波振幅比和能量比异常特征研究     

尹志文  李萍 《高原地震》2001,13(4):47-51

利用中国数字地震台网（CDSN）兰州台记录的短周期数字地震资料，测定了尾波最大振幅与S波最大振幅之比r1、尾波能量与S波能量之比的平方根值r2随时间的变化。结果表明：在永登主震（19950和天祝-古浪主震（1996）前，r1和r2均出现上升或下降异常变化，且有较大的偏离平均值的异常高值或异常低值出现。  相似文献   

地震波形群体特征在强余震预测中的应用     

陈宇卫  刘文龙 《地震地磁观测与研究》1995,16(4):43-47

研究了华东地区１５个地震序列的振幅比、初动方向和初动半周期资料。得到：大震（主余型序列中的主震或震群型序列中最大地震）前后的Ｐ波初动方向，除人们熟知的由优势分布转化为紊乱外，还有可能呈优势分布，优势方向改变的特征。余震序列的Ｐ波初动方向和振幅比特征可能有助于预测强余震。初动半周期特征可能用于区别的前震和余震。  相似文献