天气雷达数据处理系统人控应用软件

天气雷达用于抗灾和减灾很重要,本文提出一种人工降雨和驱冰雹软件,给出了程序流图,对编程的关键进行了分析,最后结果表明它能提高人控作业效率。     

Geomorphic characteristics of the Minjiang drainage basin (eastern Tibetan Plateau) and its tectonic implications: New insights from a digital elevation model study

Abstract   The Minshan Mountain and adjacent region are the major continental escarpments along the eastern Tibetan Plateau. The Minjiang drainage basin is located within the plateau margin adjacent to the Sichuan Basin. Based on the analysis of the digital elevation model (DEM) acquired by the Shuttle Radar Topography Mission (SRTM), we know that the Minjiang drainage basin has distinct geomorphic characteristics. The regular increasing of local topographic relief from north to south is a result of the Quaternary sediment deposition within the plateau and the holistic uplift of the eastern margin of the Tibetan Plateau versus the Sichuan Basin. Results from DEM-determined Minjiang drainage sub-basins and channel profiles show that the tributaries on the opposite sides are asymmetric. Lower perimeter and area of drainage sub-basins, total channel length and bifurcation ratio within eastern flank along the Minjiang mainstream are the result of the Quaternary differential uplift of the Minshan Mountain region. Shorter stream lengths and lower bifurcation ratio might be the indications of the undergrowth and newborn features of these eastern streams, which are also representative for the eastern uplift of the Minshan Mountain.     

鄂西北夏季对流降水回波特征的研究

该文通过对鄂西北1995～1999年6～9月273个对流回波个例进行统计分析，得出生成对流云的主要天气背景为西风低槽过境和副高外围的影响。对流云回波出现频率6、9月较少，7～8月较多。当地地形对对流云活动具有促进生成、约束移动、抬升加强等作用。对流云可分为单体、多单体、超级单体和混合云中对流等种类。6、9月对流云平均的生命时间较短，回波强度、顶高和强回波区顶高较低。相反，7～8月对流云回波特征值较高     

Optical polarization of the Crab pulsar: precision measurements and comparison to the radio emission

The linear polarization of the Crab pulsar and its close environment was derived from observations with the high-speed photopolarimeter Optical Pulsar TIMing Analyser at the 2.56-m Nordic Optical Telescope in the optical spectral range (400–750 nm). Time resolution as short as 11 μs, which corresponds to a phase interval of 1/3000 of the pulsar rotation, and high statistics allow the derivation of polarization details never achieved before. The degree of optical polarization and the position angle correlate in surprising details with the light curves at optical wavelengths and at radio frequencies of 610 and 1400 MHz. Our observations show that there exists a subtle connection between presumed non-coherent (optical) and coherent (radio) emissions. This finding supports previously detected correlations between the optical intensity of the Crab and the occurrence of giant radio pulses. Interpretation of our observations requires more elaborate theoretical models than those currently available in the literature.     

模拟倾斜界面情况下区域地震范围内的长周期Pnl波

中国大陆地壳厚度的特点是东部地区薄西部地区厚,因此在计算Pnl波的Green函数时进一步考虑了莫霍界面倾斜的影响.本文将广义射线理论推广到倾斜层结构模型,该方法的计算结果与有限差分的计算结果有很好的一致性.理论计算表明,在同一个倾斜结构模型中沿相反方向传播的Pnl波有明显的差异.因此当地壳厚度的变化不能忽略时,根据水平层模型的理论计算结果拟合Pnl波记录时效果不够理想.对菏泽、门源地震资料的处理结果表明,用一个更接近实际地壳的倾斜层模型来拟合Pnl波比用等效厚度平行层模型来拟合要更为合理.     

ERS-2 SAR反演海洋风矢量的研究

SAR(Synthetic Aperture Radar)反演海洋风矢量是当今微波遥感领域非常有意义的前沿课题. 本文首先介绍了星载SAR估算海面风向、风速的基本原理和三种主流反演算法,接着给出反演的流程图以及重要步骤. 然后,以2002年5月7日香港地区ERS-2 SAR海洋图像为例,对经典的SWDA (SAR Wind Direction Algorithm)－谱分析方法加以改进,求得具有180°模糊度的风向,并用香港天文台气象浮标实测数据消除了风向不确定性. 最后,利用CMOD4 GMF（Geophysical Model Function,地球物理模式函数）计算得到海面上10m高的风速. 与气象浮标站实测资料相比,利用ERS-2 SAR图像获取的海面风向、风速的精度均较高. 这一结果表明：如果对SAR预先进行ADC(Analog to Digital Converter)改正以及精确校准,结合改进的SWDA和CMOD4,可以获得高精度的风矢量.     

湘中“6.26”雷雨大风过程的多普勒雷达产品分析

对6月26日发生在湘中的一次大风过程进行多普勒天气雷达回波分析发现,中低层切变线、地面干线和较强垂直风切变是发生大风的主要背景形势,回波的快速移动、     

3维块匹配小波变换的极化SAR非局部均值滤波

极化合成孔径雷达(SAR)图像受相干斑噪声的影响,难以很好地保持结构特性,针对这个问题提出了一种采用3维块匹配小波变换的非局部均值滤波算法NL-3DWT(Nonlocal Filter based on 3-D Patch Matching Wavelet Transform)。该算法使用块匹配的3维非抽样小波变换对极化总功率图进行预滤波,在此基础上使用边界对齐窗提取结构相似像素,同时使用Sigma范围选择极化SAR数据的散射相似像素,共同构成相似像素集合;构建结构保持权重函数增大图像结构信息在块相似性度量时的权重,最终实现极化SAR图像结构保持的相干斑抑制。该算法增强了图像结构特征的表达,提高了结构相似像素选择的准确性,机载极化SAR数据实验结果表明,NL-3DWT算法能够在抑制相干斑噪声的同时,更有效地保持极化SAR图像的结构特性和极化散射特性。     

极化SAR干涉测量模拟研究

极化SAR干涉测量将极化测量技术和干涉测量技术巧妙地结合,能够提高干涉测量精度,尤其是在植被覆盖的情况下,不仅能够测量地表地形,而且使得估计植被高度成为可能。因此,近几年来国际上对极化SAR干涉测量技术的研究越来越重视,极化SAR干涉测量已成为SAR应用技术发展的重要方向。通过模拟技术深入研究极化SAR干涉测量理论和方法,并提出了一种新的极化SAR干涉测量改进算法,模拟实验结果表明,该算法可以进一步提高测量精度。     

物元可拓法在地下水水质评价中的应用

可以从定性、定量两个角度解决问题的物元可拓法已被广泛应用于各个领域,本文对物元可拓法进行了改进,并应用于地下水水质评价,同时采用模糊综合评判方法进行了验证.Piper-三线图显示,研究区地下水主要为HCO3-Na和HCO3-Ca·Na型水,水质本底条件较好.水质评价结果表明,上第三系馆陶组地下水水质显著优于明化镇组,1984～1999年间明化镇组和馆陶组的地下水水质均有变坏趋势,前者趋势较为明显.物元可拓法采用综合关联度与可拓指数判断地下水水质级别,不仅能反映其相对性,也能反映绝对性,可延拓连续的特点使其更有说服力.