【作者】 耿建军；

【导师】 顾松山； 陈钟荣；

【作者基本信息】 南京信息工程大学 ， 大气物理学与大气环境， 2006， 硕士

【摘要】 目前,在新一代多普勒天气雷达已投入业务使用的气象台站中,气象工作者对雷达回波的强度和多普勒速度信息进行了大量的研究,但对于谱宽这一多普勒雷达特有信息的研究还不多见。本文试图利用在强对流天气过程发生前晴空回波中的谱宽信息,从中提取出对恶劣天气预报预警有用的信息因子,期望对提前短时天气预报时间的研究有所帮助。 第一章首先介绍了国内外天气雷达的发展、本文研究工作的意义和国内外的进展情况。 第二章对天气雷达晴空回波及其成因进行分析,认为高灵敏度脉冲多普勒天气雷达观测到的边界层大气中的非降水、非鸟类、非昆虫等原因产生的晴空雷达回波是由于电磁波投射到折射率随机分布不均匀的湍流介质上产生散射造成的,随之介绍了湍流及其指标特征量,根据湍流能谱理论,引入柯尔莫戈洛夫的相似性假设,对湍流惯性平衡区进行初步分析,得出雷诺数越大,则湍能耗散尺度越小,湍能串级输送越强,湍能耗散率亦越大的结论。 第三章对新一代天气雷达多普勒信息(速度和谱宽数据)的提取方法进行说明并通过推演电磁波折射率有起伏大气的反射率以-1/3次幂的规律随波长变化的关系式,验证新一代天气雷达探测晴空回波的能力。 第四章分析引起多普勒天气雷达探测到的谱宽展宽的因素,并得出谱宽数据与表征湍流强度的湍流耗散率的关系,为下文的计算提供理论依据。 第五章利用广州新一代天气雷达(CINRAD/SA)于2004年8月11日下午强对流天气现象发生前观测到的晴空回波谱宽资料,经过数据质量控制和预处理,估算不同探测仰角高度的湍流耗散率,发现这次强对流天气过程发生前,低层的湍流耗散率明显增强;突出地揭示了这次强对流天气过程的前兆特征。 第六章总结全文并对今后的工作进行展望。更多还原

【Abstract】 Now the construction of the new generation Doppler weather radar (NEXTRAD) network which is composed of 158 S-band and C-band coherent Doppler weather radar has been nearly completed. Up to date in the weather sites where the NEXRAD have been operated, the meteorological workers and researchers have studied on the intensity and Doppler velocity information which relate to severe weather, while there are few research on spectrum width information, the unique character, obtained from Doppler radar. In this paper, one method is induced to extract a useful factor forecasting and warning severe weather from the spectrum information which is attained in clear-air echo before severe convection occur, excepting it will improve the short-term forecast to some extent.In chapter one, the development of weather radar at home and abroad, the purposes of this research and structures of this research are given.Clear-air echo concept is induced and the cause of its formulation is analyzed in chapter two. It is believed that the clear-air echo which is non-birds, non-insects, non-airplane echo in boundary layer detected by high sensitive pulse Doppler weather radar are formulated by the scattering when the electromagnetic wave irradiate on the turbulent mass and its refraction index is non-homogeneous random distributed. And then turbulence and its character are concerned. According to the turbulent spectrum theory, the Kolmogorov’s similarity hypothesis is induced to analyze the turbulent inertial range, and it is concluded that as the Reynolds number increases the turbulent energy cascade transportation will be strengthened and the rate of turbulent energy dissipation will be larger.Then in chapter three, it is described that the method to extract the CINRAD’s information (Doppler velocity and spectrum width data). And then by deducing the formula to show the -1/3 exponent rule of the refract index varying according towavelength, this paper verifies the ability of detecting the clear-air echo using weather radar.Subsequently, the factors affecting the spectrum width are discussed in chapter four. Then the relation in the form of theory formula between the spectral data and the turbulent energy dissipation rate e is provided.In chapter five, we use the clear-air echo spectrum width data acquired by CINRAD/S A in Guangzhou during the severe weather procedure occurred on August 11, 2004 to do some study work. The quality control of data is pre-processed and the turbulence energy dissipation rates of different lower angle are calculated according to the formula as foregoing. It can be found that the rate of turbulent energy dissipation in lower layer is reinforced before the rough weather system came. It distinctly exposes the noticeable character before this severe weather event.Finally, in chapter six the conclusions in this paper are showed and the future refinement is suggested.更多还原