多普勒天气雷达原始资料索引数据库设计

针对我国现阶段多普勒天气雷达网建设过程中雷达原始资料状况及气象业务发展、教学、科研工作对该类资料的管理需求．尝试设计了适于我国日前布网多普勒天气雷达原始资料的索引数据库管理系统，该系统同样可供由不同类型雷达构成的区域雷达网、全国雷达网雷达原始资料管理作参考。该数据库系统的建立采用结构化程序设计，用Visual C^ 6．0作为应用程序的开发工具，用Microsoft Access 2000做数据库。实现了雷达资料信息入库，修改，查询，资料导出，资料转换，资料回放，数据库备份等功能。     

雷达和卫星资料在中尺度模式中的初步应用

本文利用非静力中尺度模式MM5对1998年7月20日－21日发生在湖北东部地区的特大暴雨过程作数值模拟，同时将不同时间的雷达和卫星资料适时加入模式改变当时模式中的水汽场，并与控制试验进行比较分析，结果表明：加入雷达和卫星资料后的数值模拟，由于修正了暴雨区及其邻近区域对流层中低层水汽场，雨区位置和雨量中心值比仅用探空资料的控制试验更接近实况。雷达与卫星资料引入模式对于24小时降雨产生的效果不同，雷达资料的影响是局部的，范围较小，卫星资料影响范围较大，而且适时加入雷达、卫星资料能够及时通过水汽场修正，使24小时预报的雨区范围和中心强度与实况更加接近，而二者结合起来的效果与降水系统的特征有关。     

青藏高原那曲地区雨季雷达回波、降水和部分热力参量的统计特征

利用1998年青藏高原地面雷达资料、探空资料和地面降水资料，计算分析了青藏高原的雷达回波、层结热力参量及其降水的统计特征。结果表明，在6月中旬青藏高原雨季来临之后，云中对流活动明显增强，雷达回波强度增大，回波顶高和回波面积增加，层结热力参量明显改变，对流凝结高度下降，气块能量增加，降水量显著增大。     

On the Role of Wind Direction in ERS SAR Signatures of Internal Waves on the Iberian Shelf

The relationship between internal wave (IW) signatures in Synthetic Aperture Radar (SAR) images and wind velocity is investigated. The effect of the wind velocity relative to the IW propagation direction on the IW signature is studied by means of a defined signature mode parameter ( S m ). S m is the parameter that quantifies the signature of the IW intensity profile in relation to the mean backscatter of the image background.

A wind contrast model based on a simple first-order Bragg scattering theory is combined with hydrodynamic modulation theory to explain the modulation of IW signatures. It takes into account the modulation of short-scale surface waves by the effect of the relative variations of wind velocity and the surface currents generated by the IWs.

It is shown that the signature mode parameter increases with the angle between the wind velocity and the IW propagation direction so that IWs propagating against the wind direction are imaged mostly as positive sign signatures, while those propagating in the wind direction are mostly negative sign signatures.     

基于高斯过程回归的SRTM数据空洞填补方法

针对现有插值方法对复杂地表模拟能力不足的问题,发展了一种基于非平稳(神经网络)核的高斯过程回归(GPR)方法,并将其应用于SRTM DEM空缺数据填补。以山区SRTM DEM的模拟数据空洞为研究对象,将GPR模拟结果与传统插值方法(TIN、SPLINE和IDW)比较表明:GPR填补精度高于传统插值方法,且空缺区域模拟曲面较好的保持了地形特征。     

基于时域有限差分法的雪花粒子群多次散射研究

为精确利用雷达回波反演雪花粒子的微物理参数,建立满足指数分布的非球形雪花粒子群模型,在94GHz频率下利用XFDTD软件计算电磁波不同入射方向下粒子群的后向散射截面,并与简单相加作比较,结果表明:同一入射方向下,粒子群多次散射效应下的后向散射截面均大于简单相加的结果;不同入射方向下,粒子群的后向散射截面表现出很大的差异。因此雷达实际探测中必须考虑多次散射和入射电磁波的方向。     

一次后向传播对流风暴特征及传播机制

利用常规观测资料、FY 4A气象卫星红外云图以及多普勒天气雷达资料，分析了2019年5月17日夜间发生在京津冀中部伴有强冰雹、短时强降水和短时大风的强对流天气过程。利用VDRAS资料与国家自动站资料进一步揭示对流风暴形成的环境条件以及后向传播的机制。结果表明：在有利于强对流发生发展的大尺度环流背景场下，京津冀中部的对流系统迅速发展。前期京津一带的强对流天气形成较强的东北风冷池出流，与渤海湾的东南气流交汇，在廊坊北京交界一带形成了向南移动的地面辐合线,并触发了对流。由于新生风暴单体与成熟风暴之间的正反馈作用，使得在廊坊北部形成东西向带状风暴系统，造成对流风暴不断向西传播。向西传播的风暴与西北东南向的平流共同作用，最终导致风暴运动方向为西南方向，成为典型的后向传播风暴。     

A meteoroid stream survey using the Canadian Meteor Orbit Radar: I. Methodology and radiant catalogue

Using a meteor orbit radar, a total of more than 2.5 million meteoroids with masses ∼10⁻⁷ kg have had orbits measured in the interval 2002-2006. From these data, a total of 45 meteoroid streams have been identified using a wavelet transform approach to isolate enhancements in radiant density in geocentric coordinates. Of the recorded streams, 12 are previously unreported or unrecognized. The survey finds >90% of all meteoroids at this size range are part of the sporadic meteoroid background. A large fraction of the radar detected streams have q<0.15 AU suggestive of a strong contribution from sungrazing comets to the meteoroid stream population currently intersecting the Earth. We find a remarkably long period of activity for the Taurid shower (almost half the year as a clearly definable radiant) and several streams notable for a high proportion of small meteoroids only, among these a strong new shower in January at the time of the Quadrantids (January Leonids). A new shower (Epsilon Perseids) has also been identified with orbital elements almost identical to Comet 96P/Machholz.     

High resolution radiant distribution and orbits of sporadic radar meteoroids

Five years of meteor orbit data from CMOR (the Canadian Meteor Orbit Radar) are used to study the high-resolution orbital structure of the sporadic meteoroid complex. The large number of high quality orbits (2.35 million) allows the orbital characteristics of meteoroids to be studied not only in the five sporadic sources accessible from the latitude of London, Ontario, Canada, but at a resolution of 2 degrees. The radiant distribution of sporadic meteors is investigated, applying corrections for observing biases, and weighting to a constant limiting mass, and to a constant limiting energy. The orbital distribution of the sporadic sources is compared to other studies. The variation of average geocentric speed, semimajor axis, eccentricity, inclination and perihelion distance with meteoroid radiant is investigated. The source of a ring depleted in meteor radiants at 55 degrees from the apex is attributed to shorter collisional lifetimes inside the ring, due to a higher probability of catastrophic collisions with particles in the zodiacal cloud for the predominantly retrograde meteoroids inside the ring.