【作者】 胡志群；

【导师】 陈舜华； 汤达章；

【作者基本信息】 南京信息工程大学 ， 大气物理学与大气环境， 2005， 硕士

【摘要】 本论文提出了从多普勒雷达基数据中提取散度值的一种改善的EVAD技术新算法-MGS法,并且根据此算法,开发出相应的可以业务化运行的雷达产品。另外,在雷达回波面积较小,用EVAD技术难以提取散度值时,本文提出了图象识别技术,用数值模拟的方法,进行散度定量化提取。论文主要包括三部分:(1) Srivastava等人提出的EVAD技术,在实际应用过程中,因经常出现病态矩阵,而无法求解。Thomas和陶玥,汤达章分别利用不同的权重函数法,解决求解问题,本文提出利用修正的Gram-Schmidt算法(MGS法)解决求解问题。并通过两个实例,根据这几种改善的EVAD方法,分别计算出大气平均散度,再用变分法对散度值进行调整,然后利用连续方程,计算大气的垂直速度,并对各种结果进行了比较分析。结果表明:本文提出的MGS法具有算法上的优越性,较简单易行,相对Thomas权重函数法,陶玥,汤达章权重函数法而言,对散度分离的稳定性较好。(2) 大量的实际探测资料证明,冷暖平流常和大尺度的辐合辐散结合在一起,应用EVAD技术,本文用数值模拟方法,分析了这种复合风场的多普勒雷达图的径向速度特征,同时分析了雨滴下落速度对这些特征的影响,根据数值模拟得到的散度变化图表,通过对雷达PPI图像的识别,可以初步定量分析出各高度的辐合(散)值的大小。(3) 为了把本论文中提出的MGS法提取散度,大气垂直速度值的科研结果业务化,本人还开发了一个从多普勒基数据中提取散度及大气垂直速度的软件,本文介绍了该软件的操作,并通过一个个例说明了软件在业务工作中的应用情况。更多还原

【Abstract】 In this paper, a new improved EVAD technique arithmetic -MGS method which can pick up the value of divergence from Doppler radar basic data is raised, and an operationalized radar product is designed according to this arithmetic. In addition, a picture identify method which utilizes data simulation to pick up divergence quantitatively is raised as well, when the area of radar echo is too little to pick up the divergence according to EVAD technique. Three aspects are introduced mainly:(l)The EVAD technique which is raised by Srivastava is often unsolvable because of usually sick matrix during practice, Thomas and Yue Tao, Dazhang Tang utilize weighted function method to solve the problem separately, in this paper, a modified Gram-Schmidt arithmetic(MGS) is introduced to solve the same problem, according to three improved EVAD methods, basing on two examples to calculate horizontal average divergences and perform alternative solution to adjust the divergences, moreover, performing equation of continuity to calculate vertical air velocities separately, all the results are contrasted and analyzed. The result indicates that MGS method which is raised in this paper is advantage on arithmetic and easier to operate contrasting with Thomas weighted function method and Yue Tao, Dazhang Tang weighted function method, which has a better stability during divergence picking up.(2)It has been proved by lots of actual detected data that thermal or cold advection often overlap with large scale of convergence or divergence, these radial velocity characters of combined wind field are analyzed performing numerical simulation method in the paper, in addition, the influence to these characters by raindrop dripping down velocity is analyzed. The value of convergence or divergence can be gotten quantitatively from identifying radar PPIpictures according to these figures portrayed by numerical simulation.(3)In order to operationalize the research result that is raised in the paper picking-up divergence and vertical air velocity according MGS method, a software which can pick up divergence and vertical air velocity from Doppler radar basic data is designed, how to operate the software is introduced in this paper, and an applicational instance is demonstrated by an actual example.更多还原