Long‐term variations and temporal scaling of hydroclimatic time series with focus on the German part of the Elbe River Basin          下载免费PDF全文

D. Markovic  M. Koch 《水文研究》2014,28(4):2202-2211

Long‐term variations and temporal scaling of mean monthly time series of river flow, precipitation, temperature, relative humidity, air pressure, duration of bright sunshine, degree of cloud cover, short wave radiation, wind speed and potential evaporation within or in vicinity of the German part of the Elbe River Basin are analyzed. Statistically significant correlations between the 2–15 year scale‐averaged wavelet spectra of the hydroclimatic variables and the North Atlantic Oscillation‐ and Arctic Oscillation index are found which suggests that such long‐term patterns in hydroclimatic time series are externally forced. The Hurst parameter estimates (H) based on the Detrended Fluctuation Analysis (DFA) indicate persistence for discharge, precipitation, wind speed, air pressure and the degree of cloud cover, all having an annual cycle and a broad low‐frequency distribution. Also, DFA H parameter estimates are higher for discharge than for precipitation. The major long‐term quasi‐periodic variability modes of precipitation detected using Singular Spectrum Analysis coincide with those detected in the discharge time series. Upon subtraction of these low‐frequency quasi‐periodic modes, the DFA H parameter estimates suggest absence of the persistence for both precipitation and discharge. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

An improved input energy spectrum verified by the shake table tests     

Ahmet Güllü  Ercan Yüksel  Cem Yalçın  A. Anıl Dindar  Hasan Özkaynak  Oral Büyüköztürk 《地震工程与结构动力学》2019,48(1):27-45

Input energy is the principal component of the energy balance equation. It is beneficial to determine, through its components, how the recoverable and irrecoverable energies are distributed within the structural elements. Several equations and attenuation relations to define mass-normalized input energy spectra exist in the literature. They are mainly proposed for elastic systems subjected to far-fault EQs. There is a lack of experimental verification of these proposed spectra. In this paper, experimental assessment was performed to the existing spectra, and further improvements were accomplished. For this purpose, steel cantilever columns were tested on the shake table for two specific historical EQs coincidently having similar spectral acceleration values. Based on the experimental results, a three-part mass-normalized relative input energy spectrum was formulated including soil type, EQ (corner period, intensity, duration, spectral acceleration, and velocity), and structural behavioral characteristics (period and structural damping). The proposed input energy spectrum was experimentally calibrated and numerically validated for various EQs featuring near- and far-field types. Analytical and experimental comparisons were made between the previously developed spectrum and the newly proposed one. The validation studies and the statistical evaluations exposed that the proposed spectrum yielded better agreement with the experimental and numerical results.  相似文献   

井下地震计的P波接收函数正演计算及其稳定性研究——以首都圈地区为例          下载免费PDF全文

郑德高  倪四道  杨卓欣  刘志 《地球物理学报》2018,61(10):3964-3979

井下地震计波形记录的P波垂向分量存在频谱极小（spectrum null）现象，导致接收函数的结果不稳定.本文以首都圈地区为例，基于平面波入射的传播矩阵理论，发展了用于计算井下地震计的接收函数正演方法.在此基础上，分析了井下地震计波形垂向分量频谱极小现象，研究其对接收函数稳定性的影响.结果表明，井下地震计波形记录垂向分量的频谱极小开始出现的频率和地震计的埋深相关.该现象可造成反卷积提取的接收函数不稳定，且不稳定情况出现在频谱极小附近的频段，可通过选择合适的高斯因子压制其对接收函数的影响.  相似文献   

我国华东与西南县域主要气象敏感性疾病变化特征及其医疗费用研究     

王嘉鑫  石彦军  卢山  冯鑫媛  王式功  张莹 《沙漠与绿洲气象(新疆气象)》2019,13(6):133-140

摘要：针对目前医疗费用不断上涨的现实问题,基于安徽省阜南县和贵州省锦屏县相关医疗机构的全部住院数据和气象资料,首先分析两县疾病谱特征,然后从季节和24节气角度,分析两县主要气象敏感性疾病（因天气和气候异常变化而诱发或加重的相关疾病）住院人次和医疗费用的变化特征以及人体舒适度对当地主要气象敏感性疾病发病的影响。结果表明,阜南县和锦屏县人群中住院人数最多的疾病分别是循环和呼吸系统两大类气象敏感性疾病,医疗费用最高的前六位疾病都包含循环、呼吸和消化系统疾病,其三者医疗费用总和分别占两县总医疗费用的44.9%和45.8%,因此,从降低医疗费用的角度来看加强这三类主要气象敏感性疾病的预防十分重要。此外,三种系统疾病医疗费用呈现出明显的季节变化特征：其中,循环系统疾病的医疗费用在季节转换期间明显高于各季节内,呼吸系统疾病冬春季的医疗费用远高于夏秋季节,消化系统疾病夏季医疗费用最高。两县9月的体感温度最接近人体最佳舒适温度,而此时上述三类疾病的住院人次及医疗费用也是相对低点。此研究结果可为当地相关疾病的适时防控、有效降低医疗费用提供科学依据。  相似文献   

基于Bagging集成学习算法的地震事件性质识别分类   总被引：1，自引：0，他引：1       下载免费PDF全文

任涛  林梦楠  陈宏峰  王冉冉  李松威  刘晓雨  刘杰 《地球物理学报》2019,62(1):383-392

地震台网在监测地震的同时记录到的非天然震动事件会对后续的科研和预报工作造成较大的影响,因此快速准确的对天然震动事件与非天然震动事件加以区分就显得尤为重要.本文针对传统人工方法识别地震事件性质的不足之处,采用Bagging机器学习算法对地震事件性质进行区分.首先选取震中距范围在80～200km内的地震数据,之后采用AIC算法自动识别P波到时,进而用处理后的数据训练模型,最后使用测试数据对模型进行评估,准确率可达85%以上.因此,本文提出的方法可以有效地对天然震动事件与非天然震动事件加以区分.  相似文献   

Characteristics of breaking irregular wave forces on a monopile     

《Applied Ocean Research》2019

The substructures of offshore wind turbines are subjected to extreme breaking irregular wave forces. The present study is focused on investigating breaking irregular wave forces on a monopile using a computational fluid dynamics (CFD) based numerical model. The breaking irregular wave forces on a monopile mounted on a slope are investigated with a numerical wave tank. The experimental and numerical irregular free surface elevations are compared in the frequency-domain for the different locations in the vicinity of the cylinder. A numerical analysis is performed for different wave steepness cases to understand the influence of wave steepness on the breaking irregular wave loads. The wave height transformation and energy level evolution during the wave shoaling and wave breaking processes is investigated. The higher-frequency components generated during the wave breaking process are observed to play a significant role in initiating the secondary force peaks. The free surface elevation skewness and spectral bandwidth during the wave transformation process are analysed and an investigation is performed to establish a correlation of these parameters with the breaking irregular wave forces. The role of the horizontal wave-induced water particle velocity at the free surface and free surface pressure in determining the breaking wave loads is highlighted. The higher-frequency components in the velocity and pressure spectrum are observed to be significant in influencing the secondary peaks in the breaking wave force spectrum.  相似文献   

宁夏石嘴山和固原大地电场资料对比分析   总被引：1，自引：0，他引：1  

卫定军 《内陆地震》2010,24(1):64-72

处理分析了2008年1~11月宁夏石嘴山和固原地震台大地电场资料,对比研究了这两个台大地电场静日变化、干扰变化及它们的频谱特性等。石嘴山和固原地震台大地电场的变化特征:①具有明显的峰谷型静日变化形态,都含有12、24、8 h等3种主周期成份;②地电暴记录清晰可见,主要以变幅增大、时间同步为特征,但两台地电暴时频谱成份存在差异;③干扰变化特征均表现为短时突跳,变幅增大。  相似文献   

西北地区东部冰雹云的卫星光谱特征和遥感监测模型   总被引：11，自引：0，他引：11  

张杰  张强  康凤琴  何金梅 《高原气象》2004,23(6):743-748

根据气象台站的冰雹观测记录,针对冰雹灾害多发的西北地区东部,选取2001—2004年间14次NOAA卫星过境的AVHRR资料,共88个样本数,对冰雹云和其他云的光谱特征进行对比分析。结果表明,雹云的热红外亮度温度的变化基本在245K以下,中红外波段反射率相对较低,基本变化在0.4及以下范围,可见光和近红外波段反射率>0.6。冰雹产生的两个重要条件是高的云光学厚度和大的云粒子有效半径共同发生的区域;西北地区冰雹发生的云顶高度基本在4.5～7km之间。根据雹云的光谱特征,确定雹暴指数及其模型阈值>0.35的冰雹监测方法,多普勒雷达回波和气象站观测结果说明,雹暴指数等多参数结合判别冰雹云效果显著。  相似文献   

消光法反演腾格里沙漠地区沙尘气溶胶谱分布   总被引：10，自引：5，他引：5  

辛金元  张文煜  袁九毅  刘立超 《高原气象》2004,23(5):654-659

对腾格里沙漠4～9月份的整层大气气溶胶的光学遥感观测结果进行了分析。结果表明,由于消光因子对大粒径粒子消光效应的不敏感性,决定了消光法仅可较好地反演粒径在0.1～5μm之间的气溶胶谱分布特征,特别是对0.1～1μm的大粒子谱分布的反演结果更为稳定;腾格里沙漠气溶胶粒度谱分布基本符合Junge谱;浮尘天气的谱分布同干洁晴好天气的谱分布有着很大的差异,浮尘天气下粒径在0.1～1.0μm的大粒子以及粒径>1.0μm的巨粒子数有明显的增加,浓度要比干洁天气下的大几个量级。在干洁晴好天气下,腾格里沙漠的气溶胶是均一的、稳定的,而且>1μm的大粒子浓度很小;气溶胶的谱分布几乎是一致的,谱形大致为Junge谱,在粒度0.4～1.0μm范围内有一明显峰值。  相似文献   

宁夏及邻区地震震源衰减模型及震源参数研究   总被引：1，自引：0，他引：1  

金春华  盛菊琴  田小慧  赵翠萍 《地震》2013,33(1):56-64

选取2003年1月至2011年12月宁夏及邻区发生的201个M_L2.0以上地震事件进行反演, 用经验格林函数计算得到本区地震震源谱衰减模型。 在已知非弹性衰减系数和场地响应的条件下, 计算得到震源谱并研究了近震震级与拐角频率、 地震矩、 震源破裂半径及应力降之间的关系。 详细分析了震源参数误差大小及各种误差影响因素。 对剩余应力降时空演化特征分析研究结果表明: 高剩余应力降集中分布在宁夏北部宁蒙交界地区、 低剩余应力降分布在宁夏中部同心、 中卫一带, 银川盆地中南部的吴灵地区和宁夏南部海原断裂带中东段剩余应力降变化较为明显, 在时间分布上这两个区域剩余应力降在中强地震前均有降低—增强的趋势。  相似文献