基于ADTD资料的浙江地区多回击地闪特征分析     

崔雪东  张卫斌  顾媛  田德宝 《气象科技》2021,49(3):491-497

利用2007—2018年浙江省ADTD闪电定位资料,分析了该地区多回击地闪分布及相关参数特征。结果表明:浙江省多回击地闪占总地闪的26.74%,其中正闪以单回击地闪为主;正、负闪平均回击数分别为1.04次和1.65次,最大回击数分别为5次和21次。回击数和地闪数存在较为一致的年际变化,正、负多回击地闪日变化分别呈多峰和单峰分布。正、负多回击地闪电流强度算术平均值分别为72.06kA和-36.89kA,回击平均强度随回击数的增加而下降,约40%的地闪过程中至少有1次继后回击强度比首次回击强;首次回击和继后回击的强度分布呈对数正态分布,集中在15～45kA之间。正、负地闪回击间隔时间算术平均值分别为125.47ms和138.14ms,几何平均值分别为56.73ms和98.95ms,回击间隔时间呈对数正态分布,平均回击间隔时间随回击数的增大而减小。多回击地闪继后回击与首次回击之间距离与回击数呈准正态分布,集中在距离为1km范围内。  相似文献   

人工触发闪电放电过程分析：Ⅱ.闪击间放电过程   总被引：4，自引：3，他引：1  

言穆私 《高原气象》1998,17(4):403-411

详细分析了一次人工闪电继后回击之间的放电过程。结果指出：“无边奄流阶段”是激发直窜先导和继后回击的重要条件。  相似文献   

Regularized joint inverse estimation of extreme rainfall amounts in ungauged coastal basins of El Salvador     

Michael J. Friedel 《Natural Hazards》2008,46(1):15-34

A regularized joint inverse procedure is presented and used to estimate the magnitude of extreme rainfall events in ungauged coastal river basins of El Salvador: Paz, Jiboa, Grande de San Miguel, and Goascoran. Since streamflow measurements reflect temporal and spatial rainfall information, peak-flow discharge is hypothesized to represent a similarity measure suitable for regionalization. To test this hypothesis, peak-flow discharge values determined from streamflow recurrence information (10-year, 25-year, and 100-year) collected outside the study basins are used to develop regional (country-wide) regression equations. Peak-flow discharge derived from these equations together with preferred spatial parameter relations as soft prior information are used to constrain the simultaneous calibration of 20 tributary basin models. The nonlinear range of uncertainty in estimated parameter values (1 curve number and 3 recurrent rainfall amounts for each model) is determined using an inverse calibration-constrained Monte Carlo approach. Cumulative probability distributions for rainfall amounts indicate differences among basins for a given return period and an increase in magnitude and range among basins with increasing return interval. Comparison of the estimated median rainfall amounts for all return periods were reasonable but larger (3.2–26%) than rainfall estimates computed using the frequency-duration (traditional) approach and individual rain gauge data. The observed 25-year recurrence rainfall amount at La Hachadura in the Paz River basin during Hurricane Mitch (1998) is similar in value to, but outside and slightly less than, the estimated rainfall confidence limits. The similarity in joint inverse and traditionally computed rainfall events, however, suggests that the rainfall observation may likely be due to under-catch and not model bias.  相似文献   

A generalized approach for long-term modelling of extreme crest-to-trough wave heights     

Felice Arena  Diego Pavone   《Ocean Modelling》2009,26(3-4):217-225

This paper deals with the long-term modelling of high sea waves. The solution is given for the return period of sea storms during which an arbitrary chosen number of waves, with crest-to-trough heights exceeding a fixed threshold, occur. This return period is derived starting from the Equivalent Triangular Storm (ETS) model, which associates a triangle to each actual storm and thus represents a significant wave height time series at a fixed location by means of a sequence of triangular storms. The short-term statistics is then applied to investigate the occurrence of large crest-to-trough wave heights during a given storm. Finally, by combining the statistical distribution of significant wave heights, the ETS model and the short-term wave statistics, the solution is given for the return periods R_N and R_N of a sea storm in which N or at least N waves higher than a fixed threshold occur. The values of R_N are then calculated, starting from data of two buoys moored in the Pacific Ocean and in the Mediterranean Sea.  相似文献   

柔性尾鳍推进装置的机构综合与优化设计   总被引：1，自引：0，他引：1  

陈先国  向忠祥 《海洋技术学报》1997,16(3):32-37

根据柔性尾鳍推进装置所需达到的性能特性要求，本文对该装置进行了机构综合与优化设计，以改善其水动力性能，提高其推进效率。  相似文献   

图像艺术风格化的研究现状     

邓盈盈  唐帆  董未名 《南京气象学院学报》2017,9(6):593-598

图像艺术风格化作为一个正在蓬勃发展的领域被越来越多的人熟知,也引起了众多学者的研究兴趣.本文总结了图片风格化的发展现状,分析了不同风格化方法的特点,指出了目前风格化方法的缺点,总结了图片风格化的发展趋势,为进一步研究图片风格化提供了方向.  相似文献   

广州珠江新城地区高建筑物雷电回击磁场分析     

殷启元  黄惺惺 《气象科技》2018,46(2):423-428

对2011—2012年广州高建筑物雷电观测站获取到的雷电回击磁场波形数据进行统计分析,选取14个高建筑物的27次闪电过程(均为负极性地闪,含回击过程112次),其中44%的闪电个例为单次地闪过程。采用小波软阈值去噪法和基础噪声归零法进行数据预处理,分析发现:选取的回击磁场波形均呈现多峰现象,鉴于高建筑物反射峰的影响,本文只统计初始峰值;选取数据的1次闪电回击次数的算术平均值为4.2次,高度200m以下的闪电过程(14次)算术平均回击次数5.1次,高度200m以上的闪电过程(13次)算术平均回击次数3.2次;建筑物越高对磁场峰值的增强作用越显著,击中200m以上的建筑物上雷电首次回击和继后回击磁场峰值几何平均值分别是200m以下的2.2倍和1.5倍;建筑物高度对回击过程磁场波头上升时间影响不大;继后回击过程磁场波头时间远小于首次回击,与回击电场波形特征一致。  相似文献   

有向拓扑的河系渐变自动绘制算法     

吴伟  李成名  殷勇  郭沛沛 《测绘科学》2016,(12):89-93

河系渐变绘制是地图制图中水系要素表达的重要方面。针对全自动河系渐变研究较少的现状,该文提出一种基于树状约束stroke特征的河系渐变自动绘制算法。该方法在深入分析有向拓扑的数据结构基础上,重点解决河口模式识别、树状约束stroke特征构建、河系层次关系建立、主支流分级渐变等问题,实现全自动河系渐变,并进行实践测试。结果表明,该算法在地图制图过程中无须对河系河源、河口识别、河系分层和河系渐变进行人工干预,自动化程度高,大幅度提升制图效率,渐变效果优于人工绘制效果。  相似文献   

基于LLS的多回击地闪及其雷电流幅值分布特征     

王学良  成勤  王清龙  余田野  张科杰  赵涛 《热带气象学报》2021,37(3):309-319

为进一步研究多回击地闪参数分布特征, 以便为雷电防护工程设计和雷电物理研究提供参考, 根据湖北省雷电定位系统(LLS)2007年1月—2018年12月监测资料, 采用计算机编程处理和数理统计方法, 对多回击地闪次数、多重回击次数和不同类型多回击地闪雷电流幅值等参数进行了统计分析。结果表明: 多回击正地闪、负地闪和总地闪次数占其地闪总数的百分比分别为2.06%、34.76%和32.64%, 多重回击次数分别占其回击总数的0.01%、0.42%和0.40%, 多回击负地闪回击次数占多回击总地闪回击总数的99.69%。首次回击强度大于后续回击强度的多回击正地闪和负地闪分别占多回击地闪总数的82.52%和57.87%;在多回击地闪后续回击中, 正地闪约有9%的后续回击强度大于首次回击强度, 负地闪约有20%的后续回击强度大于首次回击强度。多回击正地闪和负地闪中值电流分别为59.30 kA和35.10 kA, 首次回击分别为90.90 kA和40.00 kA, 后续回击中分别为43.90 kA和33.00 kA。首次回击中, 多回击正地闪和负地闪雷电流幅值大于100 kA的累积概率分别为44.06%和4.64%, 首次回击强度大于后续回击强度的多回击正地闪和负地闪雷电流幅值大于100 kA的累积概率最大分别为52.21%和7.94%;后续回击中, 多回击正地闪和负地闪雷电流幅值小于等于40 kA的累积概率分别为41.80%和69.92%, 首次回击强度大于后续回击强度的多回击负地闪, 雷电流幅值小于等于40 kA的累积概率最大为77.71%。多回击正地闪和负地闪后续回击与首次回击中值电流的比值分别为0.48和0.83。拟合得出的不同类型的多回击正地闪和负地闪雷电流幅值累积概率公式, 拟合效果显著; 拟合公式中a值附近的雷电流幅值累积概率与b值呈显著正相关关系。   相似文献   

A stroke-based method for automated generation of schematic network maps     

Zhilin Li 《International journal of geographical information science》2013,27(11):1631-1647

This article deals with the graphic simplification of a network by schematization. A new method employing a stroke-based and progressive strategy is proposed to generate schematic network maps. This method treats a stroke (which is a long line with segments concatenated together) as a basic unit for the implementation. The procedure is as follows: (a) strokes are formed from line segments, (b) the strokes are re-orientated along grid lines and/or diagonals, and (c) two endpoints and all intersection points on (sub-)strokes are projected onto re-oriented straight lines, and (d) spatial inconsistency is detected and resolved. A methodology for each of these steps is described. This new method has been tested with a set of real-life road network data and evaluated by fractal analysis and empirical study. Experimental results show that this new method is more effective than segment-based methods and is able to produce graphics with great simplicity and clarity. Based on the results obtained, the stroke-based schematization with four primary directions is recommended.  相似文献