Forecasting flood disasters using an accelerated genetic algorithm: Examples of two case studies for China     

Ju-Liang Jin  Jian Cheng  Yi-Ming Wei 《Natural Hazards》2008,44(1):85-92

This article discusses a rescaled range analysis model, titled AGA-R/S, that is based on an accelerated genetic algorithm. The parameter a, Hurst index of rescaled range analysis, and the recurrent time of disaster in the next time-period, were directly computed using an accelerated genetic algorithm developed by the authors. As case studies, using the AGA-R/S model, a forecast was made of the tendency for change in a time series of annual precipitation for the city of Jinhua, China. The model also forecast flooding-disaster in the city of Wuzhou, China. Results indicate that it is a relatively efficient technique to forecast the change-tendency of flood and disaster time series using the AGA-R/S model. When time series is utilized, forecasted error of the AGA-R/S model is less than with a linear least square method. The Hurst indexes of the two cities are from 0.23 to 0.24, which indicates that these time series are fractal and relatively long-term. Their fractional Brownian motion shows anti-persistence. AGA-R/S has application in forecasting the change-tendency of other natural disaster for specific time series.  相似文献   

近44a毛乌素沙地西缘气候特征及其未来可能变化趋势   总被引：1，自引：0，他引：1  

安莉娟 《沙漠与绿洲气象(新疆气象)》2017,11(4):25-31

利用1971—2014年毛乌素沙地西缘气象观测资料,分析了该地区的气温、降水、相对湿度的时空变化特征,运用R/S分析法预测未来毛乌素沙地西缘气候要素可能变化趋势。结果表明:(1)近44 a毛乌素沙地西缘气温呈显著上升趋势,降水量呈弱的增加趋势,相对湿度呈弱的下降趋势,但是二者趋势并不显著。(2)近44 a毛乌素沙地西缘气温空间分布呈南高北低,降水和相对湿度均呈东多西少,各地气候倾向率存在明显的差异性,中部气温增幅较大,东部降水增加较多,南部相对湿度减少较多。(3)近44 a来毛乌素沙地西缘各气象要素变化均表现出一定的周期性,年平均气温主要存在4~5、8~10 a的振荡周期,降水量主要存在3~4、6~8 a振荡周期,相对湿度主要存在2~4、6~8 a的振荡周期。(4)毛乌素沙地西缘未来气温仍呈上升趋势可能性较大,未来降水量可能变为减少趋势,未来相对湿度变化不稳定。  相似文献   

Factors influencing long range dependence in streamflow of European rivers          下载免费PDF全文

E. Szolgayova  G. Laaha  G. Blöschl  C. Bucher 《水文研究》2014,28(4):1573-1586

Investigating long range dependence of river flows, especially in connection with various climate and storage related factors, is important in order to improve stochastic models for long range dependence and in order to understand deterministic and stochastic variability in long‐term behaviour of streamflow. Long range dependence expressed by the Hurst coefficient H is estimated for 39 (deseasonalized) mean daily runoff time series in Europe of at least 59 years using five estimators (rescaled range, regression on periodogram, Whittle, aggregated variances, and least squares based on variance). All methods yield estimates of H > 0.5 for all data sets. The results from the different estimators are significantly positively correlated for all pairs of methods indicating consistency of the methods used. Correlations between H and various catchment attributes are also analysed. H is strongly positively correlated with catchment area. Apparently, increasing storage with catchment area translates into increasing long range dependence. H is also positively correlated with mean discharge and air temperature and negatively correlated with the mean specific discharge and the seasonality index (maximum Pardé coefficient). No significant correlation is found between the Hurst coefficient and the length of the analyzed time series. The correlations are interpreted in terms of snow processes and catchment wetness. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

连云港水文序列Hurst系数的子波估计     

胡志晖  孙克渠  茆海云  张瑞光 《海洋预报》2007,24(4):97-101

在水文序列的研究中引入了Hurst系数的子波估计法,对月平均海水温度序列计算了Hurst系数的子波估计值。  相似文献   

成矿元素品位有序数据集自仿射分形方法应用性评价   总被引：1，自引：0，他引：1  

万丽  王庆飞 《地球科学进展》2007,22(4):357-361

自仿射分形的Hurst指数是分析地质剖面数据的有利参数。以大尹格庄金矿不同勘探线刻槽取样所得的金品位序列为例，评价Hurst指数的几种估算方法在地质剖面数据分析中的适用性。取相同尺度，全部数据集的增量标准偏差法统计散点呈波状变化，部分数据集的曲线长度变换法统计散点的后半部分呈波状变化,全部数据集的重标极差分析法统计散点线性拟合较好。结果显示增量标准偏差法对尺度要求较为苛刻，适于巨量数据的统计；曲线长度变换法应用性较广，所得Hurst指数反映品位的空间变化强度；重标极差分析法稳定性最好，其Hurst指数反映了品位变化相依性。   相似文献   

全球气温变化的多分形谱   总被引：9，自引：0，他引：9  

江田汉  邓莲堂 《热带气象学报》2004,20(6):673-678

运用计算多分形谱的多分形非趋势波动分析法，研究全球、北半球和中国月平均温度距平的多分形特征。全球气温、北半球气温和中国气温的变化是自相似的多分形；它们都表现出一定的正长程相关性，全球气温的长程相关性最强，北半球次之，中国气温相对最弱；中国气温的最强涨落较北半球气温大，而全球气温的最强涨落最小。  相似文献   

地震活动性参数的变尺度（Rem>/Sem>）分析   总被引：7，自引：0，他引：7       下载免费PDF全文

李娟  陈颙 《地震学报》2001,23(2):143-150

将改变时间标度的方法应用于地震活动性分析中，选择具有不同空间尺度范围、时间范围和地震活动背景的现代仪器地震目录作为研究对象，分析了几个地震活动性参数——地震频度和地震发生时间间隔与时间标度的关系．这些地震活动性参数的极差和均方差之比与时间标度呈现出幂指数变化方式，且幂指数都大于0.5，表明地震的发生并非无记忆的泊松过程，而是具有随机和规律的双重特性．犎指数偏离0.5的程度可以衡量随机与规律成分所占比重，偏离越大，该序列的规律性成分越多，反之则越少．通过时间标度变换，可以较短时间的观测为基础，对变量未来的发生情况做出保守的估计．   相似文献   

Hurst指数估计中存在的若干问题——以在气候变化研究中的应用为例   总被引：40，自引：0，他引：40  

江田汉  邓莲堂 《地理科学》2004,24(2):177-182

用7种方法估计中国近百年月平均温度距平序列的Hurst指数,并用随机重排法与高斯随机数做均值对比。结果表明:R/S分析法、小波分析法和Whittle法优于残差方差法、绝对值法、聚合方差法和周期图法;中国近百年月平均温度距平序列的Hurst指数的估计值约为0.76±0.003,表现出较强的持续性。未来中国月平均温度变化将与自20世纪80年代增温的趋势一致,将来整体趋势还是增温。  相似文献   

Seismic directional random noise suppression by radial‐trace time–frequency peak filtering using the Hurst exponent statistic          下载免费PDF全文

Chao Zhang  Hongbo Lin  Baojun Yang 《Geophysical Prospecting》2016,64(3):571-580

Radial‐trace time–frequency peak filtering filters a seismic record along the radial‐trace direction rather than the conventional channel direction. It takes the spatial correlation of the reflected events between adjacent channels into account. Thus, radial‐trace time–frequency peak filtering performs well in denoising and enhancing the continuity of reflected events. However, in the seismic record there is often random noise whose energy is concentrated in certain directions; the noise in these directions is correlative. We refer to this kind of random noise (that is distributed randomly in time but correlative in the space) as directional random noise. Under radial‐trace time–frequency peak filtering, the directional random noise will be treated as signal and enhanced when this noise has same direction as the signal. Therefore, we need to identify the directional random noise before the filtering. In this paper, we test the linearity of signal and directional random noise in time using the Hurst exponent. The time series of signals with high linearity lead to large Hurst exponent value; however, directional random noise is a random series in time without a fixed waveform and thus its linearity is low; therefore, we can differentiate the signal and directional random noise by the Hurst exponent values. The directional random noise can then be suppressed by using a long filtering window length during the radial‐trace time–frequency peak filtering. Synthetic and real data examples show that the proposed method can remove most directional random noise and can effectively recover the reflected events.  相似文献   

The scientific legacy of Harold Edwin Hurst (1880–1978)     

P.E. O’Connell  D. Koutsoyiannis  H. F. Lins  Y. Markonis  A. Montanari  T. Cohn 《水文科学杂志》2016,61(9):1571-1590

ABSTRACT

Emanating from his remarkable characterization of long-term variability in geophysical records in the early 1950s, Hurst’s scientific legacy to hydrology and other disciplines is explored. A statistical explanation of the so-called “Hurst Phenomenon” did not emerge until 1968 when Mandelbrot and co-authors proposed fractional Gaussian noise based on the hypothesis of infinite memory. A vibrant hydrological literature ensued where alternative modelling representations were explored and debated, e.g. ARMA models, the Broken Line model, shifting mean models with no memory, FARIMA models, and Hurst-Kolmogorov dynamics, acknowledging a link with the work of Kolmogorov in 1940. The diffusion of Hurst’s work beyond hydrology is summarized by discipline and citations, showing that he arguably has the largest scientific footprint of any hydrologist in the last century. Its particular relevance to the modelling of long-term climatic variability in the era of climate change is discussed. Links to various long-term modes of variability in the climate system, driven by fluctuations in sea surface temperatures and ocean dynamics, are explored. Several issues related to the Hurst Phenomenon in hydrology remain as a challenge for future research.