基于改进全变差正则化的GPR多尺度全波形双参数同步反演          下载免费PDF全文

王珣  冯德山  王向宇 《地球物理学报》1954,63(12):4485-4501

针对探地雷达（GPR）双参数全波形反演中电导率反演精度差、双参数存在串扰现象、反演计算量大、易陷入局部极值等问题.作者将具有多参数调节功能的L-BFGS算法引入到GPR时间域全波形反演中,它避免了对Hessian矩阵的直接存储与精确求解,减小了存储量和计算量.结合参数调节因子的选取,有效减小了同步反演时介电常数与电导率的串扰影响,在不降低介电常数反演精度的前提下,提高电导率参数的反演精度.通过在反演目标函数中加载改进全变差正则化方法,提高了反演的稳定性,使目标体边缘轮廓更加清晰.首先以简单模型为例,对比了单尺度反演与多尺度串行反演策略的优劣,说明多尺度串行反演有利于逐步搜索全局最优解;而开展参数调节因子的选取实验,说明合适的参数调节因子可以有效改善介质电导率的反演精度;测试了不同正则化的反演效果,表明改进全变差正则化能提高反演稳定性,显著降低模型重构误差.最后,分别对含噪合成数据和实测数据进行了反演测试,说明本文提出的多尺度、双参数反演具有较强的鲁棒性,能提供更丰富的信息约束,重构图像界面清晰、反演效果好.  相似文献   

TYPHOON ACTIVITY IN NORTHWEST PACIFIC IN RELATION WITH EL NINO AND LA NINA EVENTS     

何敏  宋文玲  陈兴芳 《热带气象学报(英文版)》1999,5(2):153-162

Statistic and typical-year composition methods are used to study the northwest Pacific typhoon activities in relation with the EI Niño and La Niña events. The result indicates that the typhoon tends to be inactive in the EI Niño years and active in the La Niña years and it is also dependent on the onset and ending time and intensity of the events and areas of genesis of typhoons. With statistic features of the frequency of typhoon activity in the EI Niño and La Niña years and the time-lag correlation between the frequency and sea surface temperature(SST), useful information is provided for the prediction of typhoon occurrence. In addition, the singular values disassemble(SVD)method is applied to study the correlation between the geopotential field and SST field. The result shows that the air-sea coupling in the EI Niño years is unfavorable for the typhoon to develop. Which take place with a smaller number. Opposite situations are found with the La Niña years.  相似文献   

石羊河流域干旱气候对ENSO事件的响应及预测分析     

罗晓玲 《沙漠与绿洲气象(新疆气象)》2020,14(4):46-51

根据石羊河流域5个气象站1961—2018年的降水、气温、干旱实况资料,利用气候统计学方法分析ENSO事件对该区气候变化及干旱的影响。结果表明:厄尔尼诺事件会造成流域春季降水偏多,春、秋、冬季气温偏高,易出现暖冬;拉尼娜事件则春季降水偏少,秋季降水偏多,冬季气温偏低,易出现冷冬,中下游发生中度以上春旱、春末夏初旱和伏旱的概率较高。应用1968—2010年旬、月气象要素和大气环流特征量,采用最优子集回归方法,建立降水和干旱统计预测模式,然后结合ENSO事件,通过加权平均法构建集成预测概念模型。对模型进行检验,拟合率与准确率较高,已投入业务使用。  相似文献   

沿海渔业天气警报服务系统     

王雪森  林朝昌 《成都信息工程学院学报》1993,(1)

本文简要地介绍了建立沿海渔业天气警报服务系统的必要性,系统的设计特点,现场试验情况以及今后建台布网的设想。特别是把短波单边带通信,地面波传播方式和双音报警技术引入天气警报服务系统,开辟了短波单边带气象通应用的新领域。  相似文献   

Lower Pleistocene deltaic and marine sediments in boreholes from the central North Sea     

Martyn S. Stoker  Alistair J. A. Bent 《第四纪科学杂志》1987,2(2):87-96

Lower Pleistocene sediments recovered in boreholes from the Aberdeen Ground Formation in the central North Sea indicate that the unit was deposited in a delta front to prodelta/shallow, open shelf marine setting. Possible estuarine and clastic nearshore marine deposits have been identified on the western margin of the basin. The delta front sediments consist of interbedded, structureless to laminated sands and muds with organic debris, ferruginous nodules and common soft sediment deformation structures. Sporadic rippled and graded beds, basal scours to beds and starved ripples suggest periodic wave–current reworking. Prodelta/shelf marine sediments are predominantly argillaceous with only occasional thin sand beds and rare phosphatic bands. One exceptionally thick sand body or submarine channel-fill although this remains uncertain. The estuarine/clastic nearshore marine sediments include coarse channel-lag deposits and rippled and laminated subtidal sands. A rich microfossil assemblage recovered from the prodelta/shelf marine sequence indicates that deposition occurred under fluctuating climatic conditions.  相似文献   

柴北缘的大地构造演化及其地质事件群   总被引：10，自引：0，他引：10  

辛后田  王惠初  周世军 《华北地质》2006,29(4):311-320

柴达木盆地北缘及邻区包括六个二级构造单元:中南祁连地块(宗务隆天山期裂陷槽)、欧龙布鲁克微陆块、柴北缘祁连期结合带、柴达木地块、东昆仑晚天山-印支期结合带(东昆北岩浆弧)和西秦岭结合带。其中柴北缘及邻区的大地构造演化,经历了前寒武纪基底成生与演化、祁连期洋-陆转化、天山-印支期板内变形和中新生代陆相盆地演化-高原隆升等四个阶段。本文在论述各个演化阶段的沉积事件、岩浆活动、变质作用、构造形迹和成矿作用等地质事件群的基础上,对柴北缘的变质基底、全球大地构造对比和显生宙花岗岩等重大基础地质问题进行了讨论。  相似文献   

铁岭市近45年气候变化特征分析   总被引：23，自引：1，他引：23  

刘敏  张耀存  周昕  张菁 《气象》2006,32(5):99-104

利用线性倾向率、滑动平均等方法，对铁岭市1960--2004年间4个气象观测站的月平均气温、降水量、平均最高气温、平均最低气温以及初终霜、无霜期、积温、透雨等资料进行分析，结果发现铁岭市近45年气候变化特点为温度呈上升、降水略减少的趋势，特别是近15年，气温增暖幅度加大，降水春夏两季减少明显；但各季增温幅度差异较大，对气候变暖贡献最大的是冬季，平均最低气温升温幅度明显高于平均最高气温，气温日较差变小；初霜拖后、终霜提前及无霜期延长，积温明显增多，透雨偏晚频率增大，极端气候事件出现的几率增大。  相似文献   

RELATION BETWEEN SUMMER TYPHOON FREQUENCY ANOMALIES IN WEST PACIFIC AND ENSO EVENTS AND THE ANOMALOUS ATMOSPHERIC CIRCULATION CHARACTERISTICS     

周学鸣  魏应植  吴陈锋 《热带气象学报(英文版)》2006,12(1):16-23

By using data of serially numbered typhoons in northwestern Pacific and NOAA OLR data and NCEP/NCAR reanalysis data of wind field, based on the statistics and study of the relationship between the calendar years with more (or fewer) summer typhoons and ENSO events, we compared the composites of OLR eigenvectors and tropical summer wind fields during El Nino and La Nina events with more or fewer than normal summer typhoons, respectively. The results show that, in summer, without remarkable systematic anomalies of Mascarene High and Australia High in South Hemisphere, the anomaly of Walker circulation will dominate and follow the rule of ENSO impacts to atmospheric circulation and typhoon frequency. Otherwise, when systematic anomalies of Australia High appear during the El Nino events, circulation anomalies in the South Hemisphere will dominate, and many more typhoons will occur. In 1999, which is a special year of La Nina events, northward and eastward monsoon was induced by the stronger Mascarene High, and fewer typhoons arose. The typhoon source are regions where weak vertical wind shear, warm pool in western Pacific and the area with monsoon troughs are overlapping with each other. Finally, this paper analyzes and compares the source locations and ranges of more (fewer) typhoons in the events of El Nino and La Nina, respectively.  相似文献   

多次覆盖技术在探地雷达勘探中的应用     

王帮兵  田钢  孙波  郭井学  张向培 《应用地球物理》2006,3(3):187-191

多次覆盖技术作为一种增强信号、压制干扰的方法,广泛用于地震勘探工作中,可以大大提高有用信号的信噪比。本文作者把多次覆盖技术引入探地雷达测量工作中,通过与剖面法作对比试验来论证多次覆盖技术在探地雷达勘探中应用的可行性及优缺点。作者根据试验资料总结探地雷达工作中雷达波传播规律、工作参数、资料处理方法,对丰富探地雷达勘探技术作了一次有益的尝试。  相似文献   

A comparative study of the design spectra defined by Eurocode 8, UBC, IBC and Turkish Earthquake Code on R/C sample buildings     

Adem Doğangün  Ramazan Livaoğlu 《Journal of Seismology》2006,10(3):335-351

Earthquake codes have been revised and updated depending on the improvements in the representation of ground motions, soils and structures. These revisions have been more frequently seen in recent years. One of the key changes in earthquake codes has been performed on the design spectra. In this paper, the design spectra recommended by Turkish Earthquake Code and three other well known codes (Uniform Building Code, Eurocode 8, and International Building Code) are considered for comparison. The main purpose of this study is to investigate the differences caused by the use of different codes in the dynamic analysis and seismic verification of given types of buildings located at code defined different sites. The differences in expressions and some important points for elastic and inelastic spectra defined by the codes are briefly illustrated in tables and figures. Periods, base shears, lateral displacements and interstory drifts for the analyzed buildings located at code defined ground type are comparatively presented.  相似文献