2004年鲁西南两次台风低压暴雨过程对比分析

对2004年鲁西南两次台风影响造成的大~暴雨过程分析结果表明,西风槽作用下的降水,若有台风低压参与,系统均得以发展,雨势进一步加强。台风低压与西风槽结合及结合点位置,对鲁西南暴雨的形成均很重要。如副高强盛西进时,一般台风低压偏西,与西风槽结合点偏西;副高东退时,结合点一般偏东。     

一种近区地表地物重力改正的方法

利用重力等值原理,求物体质心的方法,针对高精度重力测量中常见的地表地形、地物的重力异常影响,提出了一种近区地表地物的改正方法。     

An analysis of anomalous weather and climate around the M S=6.2 earthquake of Zhangbei region

Through analysis we found that some mesoscale anomalous regions (10¹–10² km) of meteorological parameters such as the special drought areas, unusual warm areas, the largest snowfall center, low pressure area together with the epicenter area of M _S=6.2 Zhangbei earthquake on January 10, 1998 are located at the same area, i.e. there appears the “Five areas corresponding” phenomenon. Meanwhile, three times of low pressure evolution are generated and develop in the earthquake area in five days after the occurrence of the earthquake. The abnormal variation of the lower limit of frozen soil layer shows indirectly that unusual warm in earthquake areas are related to the upward thermal conduction from the deeper layer of earth surface.     

Modelling of the spatial evolution of extreme laboratory wave crest and trough heights with the NLS-type equations

The statistical properties of long-crested nonlinear wave time series measured in an offshore basin have been analyzed in different aspects such as the distributions of surface elevation, wave crest, wave trough, and wave period. Comparison with linear, second-order and third-order theoretical models indicates that although bound wave effects also contribute to the deviation from a Gaussian process, it is the modulational instability that primarily determines the discrepancy in the evolution process in the presence of strong nonlinearity. Interestingly enough, wave crest is more sensitive to the quasi-resonant four-wave interaction effect than wave trough and the scaled maximal wave crest presents a linear regression model with the coefficient of kurtosis. Meanwhile, the estimation of the observed statistical properties is reconstructed on the basis of an ensemble of 100 wave series simulated by the NLS-type equations and compared favourably with the experimental results in most cases. Moreover, with the increased third-order nonlinear effect the difference between NLS and Dysthe simulations is enlarged and mainly reflected on the distribution of wave crest.     

季风低压对台风生成影响的观测分析

选取2007年和2009年发生的4个季风低压个例, 利用FNL资料和CMORPH卫星反演的降水资料, 采用多尺度环流分析法, 对西北太平洋季风环流的多尺度特征进行了分析, 研究季风低压对台风生成的可能影响。分析发现:季风低压生成于季风槽中, 其天气尺度波列的气旋性环流中。虽然以季风槽为特点的低频环流为台风生成提供大尺度气候条件, 但是季风低压通过进一步提供较大的正相对涡度, 可以有效减小Rossby变形半径, 促进热带低压中中尺度对流系统的相互作用和合并, 有利于台风的生成。     

数字地形测图之野外设站检查方法

根据《数字测绘产品检查验收规定和质量评定》(GB/T 18316—20010),探索利用数字地形测图成果的野外检查数据与提取地形图数据进行自动计算、分析比较、统计制表的精度检查方法。     

Propagation of vertical and horizontal source data errors into a TIN with linear interpolation

Digital elevation models (DEMs) have been widely used for a range of applications and form the basis of many GIS-related tasks. An essential aspect of a DEM is its accuracy, which depends on a variety of factors, such as source data quality, interpolation methods, data sampling density and the surface topographical characteristics. In recent years, point measurements acquired directly from land surveying such as differential global positioning system and light detection and ranging have become increasingly popular. These topographical data points can be used as the source data for the creation of DEMs at a local or regional scale. The errors in point measurements can be estimated in some cases. The focus of this article is on how the errors in the source data propagate into DEMs. The interpolation method considered is a triangulated irregular network (TIN) with linear interpolation. Both horizontal and vertical errors in source data points are considered in this study. An analytical method is derived for the error propagation into any particular point of interest within a TIN model. The solution is validated using Monte Carlo simulations and survey data obtained from a terrestrial laser scanner.     

环抱式防波堤口门航道横流三维特性研究

环抱式防波堤口门易出现较大横流,且三维特性明显。针对连云港主港区深水航道,建立三维潮流数学模型,并用现场航槽实测资料进行验证,在此基础上计算分析了不同潮差条件下口门段进港航道横流的三维特性。研究结果表明:最大横流约出现在高潮位前1.5 h,自表层至底层相继出现,且表、底层出现时刻仅相差0.5 h;因航道边坡较小,最大横流时未见水流分离现象,航槽底部没有反向流;各层最大横流值均与涨潮潮差有关,且相关程度高;航道内最大横流垂向分布梯度随潮差增加略有增大。     

航空矢量重力测量水平分量的带限直接地形影响

基于第二类Helmert凝聚法的级数展开式,独立推导了航空矢量重力测量水平分量带限直接地形影响的计算公式。在中国西部山区选取了两条沿纬圈方向4000m航线高度上的航线,采用 的数字高程模型基于解析核计算了水平分量的直接地形影响,经低通滤波后与基于带限公式计算的地形影响进行了比较。数值计算结果表明,二者吻合较好,本文给出的带限地形影响公式可用于航空矢量重力测量水平分量的地形归算。     

西安市一次短时强风暴天气过程分析

1997年7月28日西安市发生一次强风暴天气过程，分析发现这次过程主要受秦岭山脉地形、地面弱冷空气南下和副高增强西进的共同影响而造成；强风暴发生在地面“人”字形辐合线交点处；由多单体雷暴演变成超级单体雷暴，在雷达回波中呈“S”型。秦岭山脉北侧边缘的对流活动是此类天气前期的一个明显征兆。