共查询到20条相似文献，搜索用时 15 毫秒
1.
Homogeneous Indian Monsoon rainfall: Variability and prediction 总被引：1，自引：0，他引：1
The Indian summer monsoon rainfall is known to have considerable spatial variability, which imposes some limitations on the
all-India mean widely used at present. To prepare a spatially coherent monsoon rainfall series for the largest possible area,
fourteen subdivisions covering the northwestern and central parts of India (about 55% of the total area of the country), having
similar rainfall characteristics and associations with regional/global circulation parameters are merged and their area-weighted
means computed, to form monthly and seasonal Homogeneous Indian Monsoon (HIM) rainfall series for the period 1871–1990. This
paper includes a listing of monthly and seasonal rainfall of HIM region. HIM rainfall series has been statistically analysed
to understand its characteristics, variability and teleconnections for long-range prediction.
HIM rainfall series isfound to be homogeneous, Gaussian distributed and free from persistence. The mean (R) rainfall is 757
mm (87% of annual) and standard deviation (S) 119 mm, with a Coefficient of Variation (CV) of 16%. There were 21 dry (K, -<R S) and 19 wet (R
i R + S) years during 1871–1990. There were clusters of frequent negative departures during 1899–1920 and 1965–1987 and positive
departures during 1942–1961. The recent three decades show very high rainfall variability with 10 dry and 6 wet years. The
decadal averages were alternatively positive and negative for three consecutive decades, viz., 1871–1900 (positive); 1901–1930
(negative); 1931–1960 (positive) and 1961–1990 (negative) respectively. Significant QBO and autocorrelation at 14th lag have
been found in HIM rainfall series.
To delineate the changes in the climatic regime of the Indian summer monsoon, sliding correlation coefficients (CCs) between
HIM rainfall series and (i) Bombay msl pressure, (ii) Darwin msl pressure and (iii) Northern Hemisphere surface air temperature
over the period 1871–1990 have been examined. The 31-year sliding CCs showed the systematic turning points of positive and
negative CCs around the years, 1900 and 1940. In the light of other corroborative evidences, these turning points seem to
delineate ‘meridional’ monsoon regime during 1871–1900 and 1940–1990 and ‘zonal’ monsoon regime during 1901–1940. The monsoon
signal is particularly dominant in many regional and global circulation parameters, during 1951–1990.
Using the teleconnections ofHIM series with 12 regional/global circulation parameters during the recent 36-year period 1951–86 regression models have been
developed for long-range prediction. In the regression equations 3 to 4 parameters were entered, explaining upto 80% of the
variance, depending upon the data period. The parameters that prominently enter the multiple regression equations are (i)
Bombay msl pressure, (ii) April 500 mb Ridge at 75°E, (iii) NH temperature, (iv) Nouvelle minus Agalega msl pressure and (v)
South American msl pressure. Eleven circulation parameters for the period 1951–80 were subjected to Principal Component Analysis
(PCA) and the PC’s were used in the regression model to estimate HIM rainfall. The multiple regression with three PCs explain
72% of variance in HIM rainfall. 相似文献
2.
Yan Jun Puah Yuk Feng Huang Kuan Chin Chua Teang Shui Lee 《Journal of Earth System Science》2016,125(2):269-283
Climate change is receiving more attention from researchers as the frequency of occurrence of severe natural disasters is getting higher. Tropical countries like Malaysia have no distinct four seasons; rainfall has become the popular parameter to assess climate change. Conventional ways that determine rainfall trends can only provide a general result in single direction for the whole study period. In this study, rainfall series were modelled using additive Holt–Winters method to examine the rainfall pattern in Langat River Basin, Malaysia. Nine homogeneous series of more than 25 years data and less than 10% missing data were selected. Goodness of fit of the forecasted models was measured. It was found that seasonal rainfall model forecasts are generally better than the monthly rainfall model forecasts. Three stations in the western region exhibited increasing trend. Rainfall in southern region showed fluctuation. Increasing trends were discovered at stations in the south-eastern region except the seasonal analysis at station 45253. Decreasing trend was found at station 2818110 in the east, while increasing trend was shown at station 44320 that represents the north-eastern region. The accuracies of both rainfall model forecasts were tested using the recorded data of years 2010–2012. Most of the forecasts are acceptable. 相似文献
3.
In this paper the scaling hypotheses are applied to annual maximum series of rainfall depth for different rainfall duration to derive the depth–duration–frequency (DDF) curve. It is shown that, based on the empirically observed scaling properties of rainfall and some general assumptions about the cumulative distribution function for the annual maximum of the rainfall depth, it is possible to derive a simple DDF relationship. This general framework provides a basis for the generation of maps that can be used to infer DDF curves at any point of a particular area. Data from a dense raingauge network in a mountainous region in north-eastern Italy (the Trentino Province) are used to clarify the methodology for the construction and regionalization of the DDF relationship. The geographical variation of short-duration (i.e., less than 60 xmin) rainfall extremes is also evaluated by using the same framework. It is found that depth–duration ratios, defined as the ratios of the t-min to the 60-min rainfall depths of the same return period, may be considered independent of return period and geographical location for any storm duration less than 60 min. 相似文献
4.
Analysis of fifty four (1951–2004) years of daily energetics of zonal waves derived from NCEP/NCAR wind (u and υ) data and daily rainfall received over the Indian landmass (real time data) during southwest monsoon season (1 June–30 September)
indicate that energetics (momentum transport and kinetic energy) of lower tropospheric ultra-long waves (waves 1 and 2) of
low latitudes hold a key to intra-seasonal variability of monsoon rainfall over India.
Correlation coefficient between climatology of daily (122 days) energetics of ultra-long waves and climatology of daily rainfall
over Indian landmass is 0.9. The relation is not only significant but also has a predictive potential. The normalised plot
of both the series clearly indicates that the response period of rainfall to the energetics is of 5–10 days during the onset
phase and 4–7 days during the withdrawal phase of monsoon over India. During the established phase of monsoon, both the series
move hand-in-hand. Normalised plot of energetics of ultra-long waves and rainfall for individual year do not show marked deviation
with respect to climatology. These results are first of its kind and are useful for the short range forecast of rainfall over
India. 相似文献
5.
Y. V. Rama Rao Lyndon Alves Bhaleka Seulall Ziona Mitchell Kelvin Samaroo Garvin Cummings 《Natural Hazards》2012,61(3):1243-1261
In the present study, diagnostic studies were undertaken using station-based rainfall data sets of selected stations of Guyana to understand the variability of rainfall. The multidecadal variation in rainfall of coastal station Georgetown and inland station Timehri has shown that the rainfall variability was less during the May–July (20–30%) of primary wet season compared to the December--January (60–70%) of second wet season. The rainfall analysis of Georgetown based on data series from 1916 to 2007 shows that El Niño/La Niña has direct relation with monthly mean rainfall of Guyana. The impact is more predominant during the second wet season December--January. A high-resolution Weather Research and Forecasting model was made operational to generate real-time forecasts up to 84 h based on 00 UTC global forecast system (GFS), NCEP initial condition. The model real-time rainfall forecast during July 2010 evaluation has shown a reasonable skill of the forecast model in predicting the heavy rainfall events and major circulation features for day-to-day operational forecast guidance. In addition to the operational experimental forecast, as part of model validation, a few sensitivity experiments are also conducted with the combination of two cloud cumulus (Kain--Fritsch (KF) and Betts–Miller–Janjic (BMJ)) and three microphysical schemes (Ferrier et al. WSM-3 simple ice scheme and Lin et al.) for heavy rainfall event occurred during 28–30 May 2010 over coastal Guyana and tropical Hurricane ‘EARL’ formed during 25 August–04 September 2010 over east Caribbean Sea. It was observed that there are major differences in the simulations of heavy rainfall event among the cumulus schemes, in spite of using the same initial and boundary conditions and model configuration. Overall, it was observed that the combination of BMJ and WSM-3 has shown qualitatively close to the observed heavy rainfall event even though the predicted amounts are less. In the case of tropical Hurricane ‘EARL’, the forecast track in all the six experiments based on 00 UTC of 28 August 2010 initial conditions for the forecast up to 84 h has shown that the combination of KF cumulus and Ferrier microphysics scheme has shown less track errors compared to other combinations. The overall average position errors for all the six experiments taken together work out to 103 km in 24, 199 km in 48, 197 km in 72 and 174 km in 84 h. 相似文献
6.
强降雨易引发大型深层老滑坡的复活变形,研究其作用机制对建立滑坡变形破坏的降雨阈值,实现滑坡灾害的预警预报具有重要意义.以三峡库区秭归县谭家湾大型深层老滑坡为例,在地表宏观裂缝时空分布规律的精细描述基础上,结合15年的人工监测和2年的实时监测数据,分析了老滑坡的复活变形特征和发展过程.通过滑坡阶跃阶段的位移与降雨（当前降雨和前期降雨）的相关性分析,提出了降雨对深层滑坡复活变形演化过程的动态作用机制.谭家湾滑坡的7次“阶跃”变形与强降雨相关,但累积位移增量与累积降雨量无明显正相关关系,水平位移增量基本相同时,累积降雨量明显不同.引起第一次阶跃变形的累积降雨量和最大日降雨量均明显大于后续阶段,可能受控于强降雨的作用机制由“孔隙渗流”为主,逐渐转变为“渗透性增加的孔隙渗流+裂隙优势流”的综合渗流模式.这对进一步深入研究强降雨诱发深层老滑坡阶跃变形的内在机理与灾害预警具有一定的理论意义和参考价值. 相似文献
7.
依据钦州市58a平均降雨量和3条入海河流控制站径流量长序列资料,采用滑动平均、线性回归、Spearman、M-K及R/S法综合分析降雨径流的趋势性及突变特征。结果表明,钦州市降雨量总体呈弱增加趋势,增加率为0.742mm/10a,而茅岭江、钦江、大风江流域径流量存在总体减少趋势,减少率分别为0.2×108m~3/10a、1.1×108m~3/10a、0.4×108m~3/10a。运用复Molet小波分析多时间尺度周期性,降雨量序列存在5个时间尺度,22a和15a时间尺度分别为序列第一、三主周期;径流量序列存在3个时间尺度,其中22a和8a时间尺度分别为径流量序列第一、二主周期。 相似文献
8.
V Satyan 《Journal of Earth System Science》1988,97(1):49-52
Aperiodicity in the time series of Indian summer rainfall for 116 years is analysed using the phase space approach. The question
whether a low-dimensional strange attractor is associated with the chaotic behaviour of the monsoon system is investigated.
It is found that a strange attractor of dimensionality around 5·1 exists and the system has 12 relevant degrees of freedom. 相似文献
9.
The time series of Indian summer monsoon rainfall for the period 1871–1989 has been analysed using the method of deterministic
chaos. It is found that a strange attractor underlies the time series implying the existence of a prediction function. This
function has been approximated by a second-degree polynomial, involving the rainfalls of the past seven years and the coefficients
have been estimated by least squares fit. The interannual variations of actual and computed rainfalls have been presented
for a comparative study. 相似文献
10.
In the study of landslides, it is generally assumed that an impermeable boundary exists at a certain depth and failure occurs at this boundary. In reality this is not always the case and failures can occur at any depth. This paper aims to study the effect of boundary conditions on landslides, using a series of seepage and stability analyses performed over a range of rainfall intensities, and for different failure mechanisms, by studying the failure time and depths corresponding to fully drained, partially drained, and impermeable boundaries. It is shown that these conditions can significantly affect the occurrence and depth of rainfall-induced landslides. 相似文献
11.
Vratislav Hurai Klaus Simon Uwe Wiechert Jochen Hoefs Patrik Konečný Monika Huraiová Jacques Pironon Jozef Lipka 《Contributions to Mineralogy and Petrology》1998,133(1-2):12-29
Globules of iron-dominated (59–69 wt% FeOtot) and titanium-dominated (43.5 wt% TiO2) oxide melts have been detected in igneous xenoliths from Pliocene-to-Pleistocene alkali basalts of the Western Carpathians.
Fluid inclusion and mineral composition data indicate immiscible separation of the high-iron-oxide melt (HIM) at magmatic
temperatures. The HIM separation occurred during clinopyroxene (augite) accumulation in an alkali trachybasalt and continued
during crystallization of amphibole (kaersutite) and K-feldspar (anorthoclase), the latter coexisting with trachyte and alkalic
rhyolite residual melts. Some HIM was also expelled from sub-alkalic rhyolite (70–77% SiO2), coexisting with An27–45 plagioclase and quartz in granitic (tonalite-trondhjemite) xenoliths. Oxygen fugacities during HIM separation range from
−1.4 to +0.6 log units around the QFM buffer. A close genetic relationship between HIM-hosted xenoliths and mantle-derived
basaltic magma is documented by mineral 18O values ranging from 4.9 to 5.9‰ V-SMOW. δD values of gabbroic kaersutite between −61 and −86‰ V-SMOW are in agreement with
a presumed primary magmatic water source. Most trace elements, except Li, Rb and Cs, have preferentially partitioned into
the HIM. The HIM/Si-melt partition coefficients for transition elements (Sc, V, Cr, Co, Ni) and base metals (Zn, Cu, Mo) are
between 2–160, resulting in extreme enrichment in the HIM. La and Ce also concentrate in the silicic melt, whereas Tb-Tm in
the HIM. Hence, the immiscible separation causes REE fractionation and produces residual silicic melt enriched in LREE and
depleted in HREE. The weak fractionation among Tb-Tm and Yb, Lu can be attributed to recurrent extraction of the HIM from
the magmatic system, while flat HREE chondrite-normalized patterns are interpreted to indicate no or little loss of the HIM.
Received: 30 September 1997 / Accepted: 23 March 1998 相似文献
12.
The relation between karst spring discharge and rainfall by cross-correlation analysis (Campania, southern Italy) 总被引：4，自引：2，他引：2
The relation between rainfall and the discharge from two springs, located at the base of different karst massifs in southern Italy, is investigated by cross-correlation analyses. Data are derived from a continuous time window of 13 years. The input signal involves multiple rainfall time series (cumulative rainfall over varying time windows), while the time series of daily spring discharges are used as the output signal. Analyses were first conducted on the unprocessed data and then on data for which linear trends and seasonal components had been removed, the latter by a spectral analysis. Analyses contributed to the investigation of the time required for water to flow through the karst aquifers at the two sites. Long time intervals of the cumulative rainfall (>60 days) appear to be the main component affecting the spring discharge hydrographs; shorter time intervals seem to be related to quick-flow paths. Some statistics about the linear regression and the meaning of the cross-correlation analysis are discussed. Cross-correlation analysis can provide strong support for identification of the main rainfall contribution and the travel time through the main infiltration pathways in aquifers. 相似文献
13.
14.
水文时间序列相似性查询的分析与研究——以漯河站、何口站汛期降雨量相似性查询为例 总被引：2，自引：2，他引：0
水文时间序列相似性查询可用于雨洪过程预测、环境演变分析、水文过程规律分析等方面.最为直接的应用是回答防汛指挥中经常问到的"当前水文过程相当于历史上哪一时期的同类过程"等问题.由于水文数据数量大、类型复杂,仅使用水文学的理论和传统统计方法加以分析,往往因为计算能力、存储能力以及算法的复杂而造成预测时间较长.在水文领域引入数据仓库和数据挖掘的理论与技术,为解决水文科学研究面临的问题提供了新的思路. 相似文献
15.
16.
Sorensen James P. R. Davies Jeff Ebrahim Girma Y. Lindle John Marchant Ben P. Ascott Matthew J. Bloomfield John P. Cuthbert Mark O. Holland Martin Jensen K. H. Shamsudduha M. Villholth Karen G. MacDonald Alan M. Taylor Richard G. 《Hydrogeology Journal》2021,29(8):2773-2787
There is a scarcity of long-term groundwater hydrographs from sub-Saharan Africa to investigate groundwater sustainability, processes and controls. This paper presents an analysis of 21 hydrographs from semi-arid South Africa. Hydrographs from 1980 to 2000 were converted to standardised groundwater level indices and rationalised into four types (C1–C4) using hierarchical cluster analysis. Mean hydrographs for each type were cross-correlated with standardised precipitation and streamflow indices. Relationships with the El Niño–Southern Oscillation (ENSO) were also investigated. The four hydrograph types show a transition of autocorrelation over increasing timescales and increasingly subdued responses to rainfall. Type C1 strongly relates to rainfall, responding in most years, whereas C4 notably responds to only a single extreme event in 2000 and has limited relationship with rainfall. Types C2, C3 and C4 have stronger statistical relationships with standardised streamflow than standardised rainfall. C3 and C4 changes are significantly (p <?0.05) correlated to the mean wet season ENSO anomaly, indicating a tendency for substantial or minimal recharge to occur during extreme negative and positive ENSO years, respectively. The range of different hydrograph types, sometimes within only a few kilometres of each other, appears to be a result of abstraction interference and cannot be confidently attributed to variations in climate or hydrogeological setting. It is possible that high groundwater abstraction near C3/C4 sites masks frequent small-scale recharge events observed at C1/C2 sites, resulting in extreme events associated with negative ENSO years being more visible in the time series.
相似文献17.
预测滑坡地下水位的动态演变过程对滑坡稳定性分析具有重要意义, 三峡库区库岸滑坡地下水位时间序列受多种因素影响, 呈现出高度非线性非平稳的特征.为对其进行预测, 提出一种基于相空间重构的小波分析-粒子群优化支持向量机(wavelet analysis-support vector machine, 简称WA-PSVM)模型.该模型引入小波变换法对地下水位序列进行时频分解, 将非平稳的地下水位序列转变为多个不同分辨率尺度下的较平稳的地下水位子序列; 然后重构各子序列的相空间, 再利用PSVM(全称support vector machine)模型对地下水位各子序列进行预测, 最后将各子序列预测值相加得到最终预测结果.以三峡库区三舟溪滑坡前缘STK-1水文孔日平均地下水位序列为例, 首先分析滑坡前缘地下水位变化的影响因素, 再将WA-PSVM模型应用于地下水位预测, 并与单独PSVM模型和小波分析-BP网络模型(wavelet analysis-back propagation, 简称WA-BP)作对比.结果表明: 滑坡前缘地下水位受降雨和库水位影响较大, 利用WA-PSVM模型对STK-1水文孔地下水位进行预测的均方根误差为0.073m、拟合优度为0.966, WA-PSVM模型预测精度高于单独PSVM模型和WA-BP模型.WA-PSVM模型解决了地下水位序列非线性非平稳的问题, 在不考虑影响因素的情况下能获得满意的预测效果, 具有较高的建模效率和较强的实用性. 相似文献
18.
The anomalies of summer rainfall (June–August) for the last 500 years in China have been estimated according to the relationship
between the instrumentally observed rainfall and the degrees of floods and droughts for the last 25 years. It is shown that
calculated anomalies of average rainfall for 10, 20 and 30 year periods have sufficient accuracies. The long-term climatic
variations for the last 500 years are discussed based on the estimated anomalies of summer rainfall of 25 stations over the
E part of China for the last 500 years. For example, there were prolonged drought in the N of China at about the end of Ming
dynasty, but there were extensive floods in China for the early times of Qing dynasty. The anomalies of rainfall for the last
500 years were averaged along latitude zone and their decade running mean were formed. It was found that the long-term variations
are very clear. The 80 year cycle is predominating. Besides, an about 200 year cycle is also shown in the charts of 50-year
mean rainfall anomalies. It is indicated that both above mentioned cycles relate closely to the solar activity. 相似文献
19.
强降雨作用下堆积层滑坡稳定性分析 总被引：2，自引：0，他引：2
强降雨作用易造成堆积层滑坡发生,带来严重的生命财产损失。基于Green-Ampt（GA）模型,同时考虑湿润锋以上饱和带渗流作用,推导了一种新的滑坡降雨入渗函数,弥补了GA模型只适用于无限长坡的不足。为考虑降雨入渗对土体条块强度的影响,采用整体抗剪强度准则评价滑坡稳定性,并在受力分析时考虑了湿润锋以上饱和带渗透力作用,建立了滑坡稳定性系数表达式。研究结果表明：滑坡降雨入渗的尺寸效应非常明显,湿润锋扩展速率随着坡长的增大而增大,当滑坡无限长时新降雨入渗模型与GA模型计算结果相同,说明GA模型是新模型的一个特例。此外,降雨初期,滑坡稳定性下降较快;随着降雨的持续,稳定性下降速率逐渐放缓。与模型试验结果对比表明,提出的降雨入渗模型和评价方法计算结果与试验揭示的现象一致,证明了该方法的可靠性。 相似文献
20.
In August 2010, extreme rainfall affected the north of the Czech Republic and caused regional floods and landslides. Three torrential debris flows originated in the Jizerské hory Mts., close to Bílý Potok on the north slope of the Smědavská hora Mt. The rainfall situation which triggered the debris flow was analyzed and compared with the rainfall situation in 1958 when a debris flow occurred in the same area. The rainfall data were obtained from rain gauges of the Czech Hydrometeorological Institute. Four rain gauges were chosen close to the Smědavská hora Mt. with data of daily amounts from 1983 to 2013 and 10-min intensity or hourly amounts from the specific period. The data from 1958 were available from three different rain gauges (only daily amounts). The data series were not complete so linear regression was applied to interpolate them. A number of analyses were carried out including daily rainfall, 2-day/3-day moving values, antecedent precipitation index (API) of 5/10/30 days, 10-min intensity, and hourly amounts, and the trigger factor of the debris flow in the study area was also investigated. It was determined that for the triggering of debris flows, both high API values as well as high-intensity short-duration rainfall is needed. It was documented that in cases of solely high API indices or high-intensity short-duration rainfalls, no debris flows were initiated. 相似文献