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1.
《水文科学杂志》2013,58(5)
Abstract Results of a study on change detection in hydrological time series of annual maximum river flow are presented. Out of more than a thousand long time series made available by the Global Runoff Data Centre (GRDC) in Koblenz, Germany, a worldwide data set consisting of 195 long series of daily mean flow records was selected, based on such criteria as length of series, currency, lack of gaps and missing values, adequate geographical distribution, and priority to smaller catchments. The analysis of annual maximum flows does not support the hypothesis of ubiquitous growth of high flows. Although 27 cases of strong, statistically significant increase were identified by the Mann-Kendall test, there are 31 decreases as well, and most (137) time series do not show any significant changes (at the 10% level). Caution is advised in interpreting these results as flooding is a complex phenomenon, caused by a number of factors that can be associated with local, regional, and hemispheric climatic processes. Moreover, river flow has strong natural variability and exhibits long-term persistence which can confound the results of trend and significance tests. 相似文献
2.
Bi Tié Albert Goula Emile Gneneyougo Soro Williams Kouassi Bernard Srohourou 《水文科学杂志》2013,58(6):1067-1080
Résumé Le changement climatique est une réalité qui affecte plusieurs variables climatiques dont les précipitations. Néanmoins, son impact sur les évènements extrêmes et en particulier sur les pluies journalières extrêmes n'est pas encore certain car peu de travaux y ont été consacrés en Afrique de l'Ouest. Dans ce contexte, il a été proposé de détecter d'éventuels tendances et ruptures dans les propriétés statistiques (moyenne, variance) des pluies journalières extrêmes à l'aide de tests statistiques locaux et régionaux. Pour détecter ces changements, les indices caractérisant la pluie maximale journalière annuelle (PJmaxan), le nombre annuel de jours de pluie dépassant 50 mm (NJsup50) et la contribution des pluies dépassant 50 mm dans les cumuls annuels (R(PJsup50/Pan)) ont été définis. L'analyse de 44 postes pluviométriques en Côte d'Ivoire sur la période 1942–2002 ne montre pas de changement généralisé ni en moyenne, ni en variance. Toutefois, en subdivisant la Côte d'Ivoire en régions climatiques homogènes, des tendances à la baisse ont été observées dans les régions IV (au Nord) et II (au Sud-Est). Editeur Z.W. Kundzewicz; Assistant editeur G. Mahé Citation Goula, A.B.T., Gneneyougo Soro, E., Kouassi, W. et Srohourou, B., 2012. Tendances et ruptures au niveau des pluies journalières extrêmes en Côte d'Ivoire (Afrique de l'Ouest). Hydrological Sciences Journal, 57 (6), 1067–1080. 相似文献
3.
《水文科学杂志》2013,58(5)
Abstract Abstract Results of studies related to the effect of snow accumulation and snowmelt on river regimes of the central Spanish Pyrenees are presented. Streamflow of the Pyrenean rivers is characterized by low and constant discharges during winter because of accumulation of snow in the basins above 1600 m a.s.l., and high and fluctuating discharges during spring due to snowmelt and rainfall. Regional discharge contrasts have been assessed in relation to the Atlantic influence and the percentage of high altitude areas in each basin. In most of the Pyrenean basins, snowmelt contributes more to the discharge than rainfall in the spring. The analysis of data shows a decrease in winter precipitation in the last 50 years causing a decrease in both winter and spring discharges and introducing changes in the distribution of streamflow throughout the year. 相似文献
4.
《水文科学杂志》2013,58(3)
Abstract The spatial distribution and trends in the frequency of precipitation extremes over the last 44 years (1960–2003), especially since 1990, have been analysed using daily precipitation data from 147 stations in the Yangtze River basin. The research results are as follows: (1) The 15 mm precipitation isohyet approximately divides the precipitation extremes (corresponding to the 95th percentile) of the stations in the middle and lower Yangtze reaches (higher) from those of the upper Yangtze reaches (lower). Also the starting time of the precipitation extremes in the middle and lower Yangtze reaches is earlier than of those in the upper Yangtze reaches. Precipitation extremes are concentrated mostly in June in the middle and lower Yangtze reaches, and July in the upper Yangtze reaches. (2) During the period 1960–2003, the first two decades had fewer precipitation extremes than the last two decades. There have been significant increasing trends and step changes in frequency of annual total precipitation extremes and precipitation extremes with a 1–5 day gap in the middle and lower Yangtze reaches. Precipitation extremes occur more frequently in shorter periods, separated by a few days. Precipitation extremes are also becoming more concentrated in the month with the highest frequency of extremes (June) in the middle and lower Yangtze reaches. In the upper Yangtze reaches, there is an upward tendency of extreme events in June. Increasing precipitation extremes in June for both the middle and lower, and the upper Yangtze reaches will increase the probability of flooding if the observed trends of the last 40 years continue into the future. 相似文献
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6.
《水文科学杂志》2013,58(1):18-37
Résumé Au cours des dernières décennies, plusieurs méthodes d'homogénéisation ont été développées pour corriger les ruptures artificielles dans les séries climatiques. Elles ont été développées dans divers pays, pour différentes situations et avec des domaines d'application différents. Cet article présente une revue exhaustive des méthodes d'homogénéisation des séries climatiques publiées dans la littérature. Une analyse critique de ces méthodes ainsi qu'une réflexion sur leur applicabilité aux séries de précipitations totales annuelles sont également présentées. 相似文献
7.
《水文科学杂志》2013,58(5)
Abstract Major floods in Europe and North America during the past decade have provoked the question of whether or not they are an effect of a changing climate. This study investigates changes in observational data, using up to 100-year-long daily mean river flow records at 21 stations worldwide. Trends in seven flood and low-flow index series are assessed using Mann-Kendall and linear regression methods. Emphasis was on the comparison of trends in these flow index series, particularly in peak-over-threshold (POT) series as opposed to annual maximum (AM) river flow series. There is a larger number of significant trends in the AM than in the POT flood magnitude series, probably relating to the way the series are constructed. Low flood peaks occurring at the beginning or end of a time series with trend may be too low to be selected for the POT analysis. However, one peak per year will always be selected for the AM series, making the slope steeper and/or the series longer, resulting in a more significant trend. There is no general pattern of increasing or decreasing numbers or magnitudes of floods, but there are significant increases in half of the low-flow series. 相似文献
8.
《水文科学杂志》2013,58(1)
Abstract Abstract The impact of climate change is projected to have different effects within and between countries. Information about such change is required at global, regional and basin scales for a variety of purposes. An investigation was carried out to identify trends in temperature time series of 125 stations distributed over the whole of India. The non-parametric Mann-Kendall test was applied to detect monotonic trends in annual average and seasonal temperatures. Three variables related to temperature, viz. mean, mean maximum and mean minimum, were considered for analysis on both an annual and a seasonal basis. Each year was divided into four principal seasons, viz. winter, pre-monsoon, monsoon and post-monsoon. The percentages of significant trends obtained for each parameter in the different seasons are presented. Temperature anomalies are plotted, and it is observed that annual mean temperature, mean maximum temperature and mean minimum temperature have increased at the rate of 0.42, 0.92 and 0.09°C (100 year)-1, respectively. On a regional basis, stations of southern and western India show a rising trend of 1.06 and 0.36°C (100 year)-1, respectively, while stations of the north Indian plains show a falling trend of –0.38°C (100 year)-1. The seasonal mean temperature has increased by 0.94°C (100 year)-1 for the post-monsoon season and by 1.1°C (100 year)-1 for the winter season. 相似文献
9.
Claude VIGUIER 《水文科学杂志》2013,58(1):21-27
Abstract The necessary and sufficient conditions for non-zero phase shift and non-zero attenuation in linear flood routing can be derived from the continuity equation alone and are found to depend on the existence of an imaginary part in the expression for frequency or in the expression for wave number. It is shown that in linear flood routing the phase lag between flow rate and area of flow is directly related to the attenuation per unit wave length. The effects of using various forms of the momentum equation, in addition to the continuity equation, are exemplified by deriving analytical expressions in terms of the frequency, both for attenuation per unit channel length and for phase shift, for the kinematic wave, the general diffusion analogy, and the complete St. Venant equation. 相似文献
10.
Abdoulaye Bedoum Bell Jean Pierre Issak Adoum Robert Mbiake Laohoté Baohoutou 《大气与海洋》2017,55(1):42-56
[Translated by the editorial staff] An analysis of climate trends and return levels for the period 1960–2008, using the ETCCDI-CLIVAR/JCOMM project approach, has been conducted for Chad, where droughts and flooding are recurrent. Using the RClimDex software, we show that almost all rainfall trends are decreasing, as in Central and Northern Africa. Rare extreme rain events (R99p) decrease significantly: 0.85?mm per decade. However, we note a slightly upward trend of 0.5 day per decade, in the number of consecutive dry days (CDD). Temperature indices are all positive except for the frequencies of very hot days (TX90p) and very cold nights (TN10p), which decrease significantly: ?0.39% day per year per decade, as in Central Africa and globally. Sequences of hot or cold days decrease as well, but by about 1% per year per decade. Return periods identified with the generalized extreme value (GEV) distributions show that they are well defined from 1 to 10 years. Extremely rare events from 10 to 50 years are associated with a mean return level of 660?mm of annual precipitation. 相似文献