Spatial and temporal variability of rainfall over different seasons influence physical, social and economic parameters. Pre-monsoon (March, April and May – MAM) rainfall over the country is highly ...variable. Since heat lows and convective rainfall in MAM have an impact on the intensity of the ensuing monsoons, hence the pre-monsoon period was chosen for the study. The pre-whitened Mann Kendall test was used to explore presence of rainfall trend during MAM. The results indicate presence of significant (at 10% level) increasing trend in two stations (Ajmer, Bikaner). The practical significance of the change in rainfall was also explored as percentage changes over long term mean, using Theil and Sen's median slope estimator. Forecast using univariate ARIMA model for pre-monsoon months indicates that there is a significant rise in the pre-monsoon rainfall over the northwest part of the country.
La variabilité spatiotemporelle de la pluviosité sur différentes saisons influence les paramètres physiques, sociaux et économiques. La pluviosité pré-mousson (mars, avril et mai – MAM) sur la région est extrêmement variable. La période pré-mousson a été choisie pour cette étude, étant donné que l’abaissement de chaleur et la pluviosité convective pour la période MAM ont un impact sur l’intensité des moussons qui suivent. Le test Mann Kendall de pré-blanchiment a été utilisé pour explorer la possibilité d’une évolution de la pluviosité pendant la période MAM. Les résultats indiquent une tendance significative à l’accroissement (à un niveau de 10 %) dans deux stations (Ajmer et Bikaner). La signification pratique du changement dans la pluviosité a aussi été explorée dans le sens de changements sur une moyenne à long terme utilisant l’estimateur de pente moyenne de Theil et Sen. La prévision utilisant le modèle ARIMA à une variable pour les mois de pré-mousson indique une augmentation significative de la pluviosité de pré-mousson dans la partie nord-occidentale de la région.
Trends in rainfall, rainy days and 24h maximum rainfall are investigated using the Mann-Kendall non-parametric test at twenty-four sites of subtropical Assam located in the northeastern region of ...India. The trends are statistically confirmed by both the parametric and non-parametric methods and the magnitudes of significant trends are obtained through the linear regression test. In Assam, the average monsoon rainfall (rainy days) during the monsoon months of June to September is about 1606mm (70), which accounts for about 70% (64%) of the annual rainfall (rainy days). On monthly time scales, sixteen and seventeen sites (twenty-one sites each) witnessed decreasing trends in the total rainfall (rainy days), out of which one and three trends (seven trends each) were found to be statistically significant in June and July, respectively. On the other hand, seventeen sites witnessed increasing trends in rainfall in the month of September, but none were statistically significant. In December (February), eighteen (twenty-two) sites witnessed decreasing (increasing) trends in total rainfall, out of which five (three) trends were statistically significant. For the rainy days during the months of November to January, twenty-two or more sites witnessed decreasing trends in Assam, but for nine (November), twelve (January) and eighteen (December) sites, these trends were statistically significant. These observed changes in rainfall, although most time series are not convincing as they show predominantly no significance, along with the well-reported climatic warming in monsoon and post-monsoon seasons may have implications for human health and water resources management over bio-diversity rich Northeast India.
Les tendances à propos de la pluviosité, des jours de pluie et des chutes de pluie maximum en 24heures ont été recherchées, par utilisation du test Mann-Kendall non paramétrique, dans vingt-quatre sites de l’Assam sub-tropical dans la région nord-orientale de l’Inde. Les tendances sont statistiquement confirmées par les méthodes paramétriques et non paramétriques et les magnitudes de tendances significatives sont obtenues au moyen du test de régression linéaire. En Assam, la pluviosité moyenne de mousson (jours de pluie) pendant les mois de mousson de juin à septembre est d’environ 1606mm (70) qui tient compte d’environ 70 % (64 %) de la pluviosité annuelle (jours de pluie). À l’échelle mensuelle, seize et dix-sept sites (sur vingt et un sites) témoignent de tendances à la diminution de la pluviosité totale (jours de pluie), parmi lesquelles on trouve une à trois tendances (sur sept) statistiquement significatives en juin et juillet respectivement. D’un autre côté, dix-sept sites témoignent de tendances à l’augmentation de la pluviosité au mois de septembre, mais aucune n’était statistiquement significative. En décembre (février), dix-huit (vingt-deux) sites indiquent des tendances à la diminution (augmentation) de la pluviosité totale, parmi lesquelles cinq (trois) tendances sont statistiquement significatives. Pour les jours de pluie au cours des mois de novembre à janvier, vingt-deux sites ou plus témoignent de tendances à la diminution en Assam, mais pour neuf (novembre), douze (janvier) et dix-huit (décembre) sites, ces tendances sont statistiquement significatives. Ces changements observés dans la pluviosité, quoique la plupart des séries temporelles ne soient pas convaincantes puisqu’elles ne sont pas significatives au cours du réchauffement climatique bien établi lors des saisons de mousson ou de post-mousson, peuvent avoir des implications pour la santé humaine et la gestion des ressources en eau sur tout le Nord-Est de l’Inde, dont la biodiversité est riche.
In the present study, an investigation has been made to study the spatial and temporal variability in the maximum, the minimum and the mean air temperatures at Madhya Pradesh (MP), in central India ...on monthly, annual and seasonal time scale from 1901 to 2002. Further, impact of urbanization and cloud cover on air temperature has been studied. The annual mean, maximum and minimum temperatures are increased by 0.60, 0.60 and 0.62°C over the past 102 years, respectively. Seasonally, the warming is more pronounced during winter than summer. The temperature decreased during the less urbanized period (from 1901 to 1951) and increased during the more urbanized period (1961 to 2001). It is also found that the minimum temperature increased at higher rate (0.42°C) followed by the mean (0.36°C) and the maximum (0.32°C) temperature during the more urbanized period. Furthermore, cloud cover is significantly negatively related with air temperature in monsoon season and as a whole of the year.
Dans la présente étude, est recherchée la variabilité spatio-temporelle dans les températures maximales, minimales et moyennes de l’air à Madhya Pradesh (MP) en Inde centrale, sur des échelles de temps mensuelle, annuelle et saisonnière, de 1901 à 2012. L’impact de l’urbanisation et de la couverture nuageuse sur la température de l’air a aussi été étudié. Les températures annuelles moyennes, maximales et minimales ont augmenté respectivement de 0,60, 0,60 et 0,62°C sur les 102 dernières années. Si l’on se place du point de vue saisonnier, le réchauffement est plus marqué pendant l’hiver que pendant l’été. La température a diminué pendant la période la moins urbanisée considérée (1901 à 1951) et augmenté pendant la période la plus urbanisée (1961 à 2001). Il a aussi été observé que la température minimale avait augmenté d’une valeur plus élevée (0,42°C), que la température moyenne (0,36°C), et la température maximale (0,32°C) et ce, durant la période la plus urbanisée. En outre, la couverture nuageuse est significativement reliée négativement à la température de l’air en période de mousson et tout au long de l’année.
In the present study, a prominent 11-year cycle, supported by the pattern of the autocorrelation function and measures of Euclidean distances, in the mean annual sunspot number time series has been ...observed by considering the sunspot series for the duration of 1749 to 2007. The trend in the yearly sunspot series, which is found to be non-normally distributed, is examined through the Mann-Kendall non-parametric test. A statistically significant increasing trend is observed in the sunspot series in annual duration. The results indicate that the performance of the autoregressive neural network-based model is much better than the autoregressive moving average and autoregressive integrated moving average-based models for the univariate forecast of the yearly mean sunspot numbers.
Dans la présente étude, un cycle remarquable de 11
ans, corroboré par le diagramme de la fonction d’autocorrélation et les mesures des distances euclidiennes dans la série temporelle du nombre annuel moyen de taches solaires ont été observés, en prenant en considération les séries de taches solaires sur la période 1749–2007. La tendance dans les séries annuelles de taches solaires dont il a été trouvé qu’elles étaient distribuées non normalement, est examinée au moyen du test non paramétrique Mann-Kendall. Une tendance à un accroissement statistiquement significatif est observée dans les séries de taches solaires sur la durée de l’année. Les résultats indiquent que la performance du modèle basé sur le réseau neuronal autorégressif est bien meilleure que les modèles basés sur la moyenne autorégressive mouvante et sur la moyenne autorégressive intégrée mouvante, pour la prévision univariée du nombre moyen de taches solaires sur l’année.
Water has always been the focus of living things and civilizations have been established mainly in areas close to water. However, to meet the growing need for water, measures were taken such as ...transporting water from areas with abundant water to areas with water scarcity. The most effective method is to examine the behavior of water in the past and to estimate its future behavior. On the other hand, excess water, which is transported at the time of a flood carries a lot of sediment and transported sediment results in significant losses during floods. Thus, it is also important to know the change of sediment transport with water over time. In addition, possible rainfall which may come in future needs to be estimated by looking also at the history of rainfall that comes with rain. Excessive rains cause flooding and sediment transported by the flood causes erosion. Therefore, in this study, the relationship among Sakarya River streamflow and sediment transported with rainfall is analyzed by applying trend analysis. The Mann-Kendall test and Spearman Rho test were used in the study. The Mann-Kendall Rank Correlation test was used to determine the trend's starting year. An analysis of test results revealed a downward trend in The Spearman's Rho test and Mann-Kendall test. In Mann-Kendall Order Correlation test conducted to obtain the starting year of the trend, a direct relationship was found among the starting years of the trend in each parameter. Thus, the trends declining also for each parameters show a direct relationship among the streamflow, sediment and rainfall. In addition, downward trends in test statistics of Sakarya River also indicate that water will decrease in next years. Thus, to leave a healthy and adequate amount of water to the next generations, Turkey should preserve and rationally use its sources.
The goal of this study was to identify the possibility of climatic trend for trimester in time serie of rainfall(1975 a 2005), applying non parametric Mann-Kendall test. The data had been gotten by ...National WaterAgency (ANA). The results indicate which the first trimester it presented no significant trend, the second equarter trimesters it presented a negative trend. In relation to third trimester the test it showed negativetrend but is not possible to prove graphically.
The existence of a trend in a hydrological time series is detected by statistical tests. The power of a test is the probability that it will reject a null hypothesis when it is false. In this study, ...the power of the parametric t-test for trend detection is estimated by Monte Carlo simulation for various probability distributions and compared with the power of the non-parametric Mann-Kendall test. The t-test has less power than the non-parametric test when the probability distribution is skewed. However, for moderately skewed distributions the power ratio is close to one. Annual streamflow records in various regions of Turkey are analyzed by the two tests to compare their powers in detecting a trend.
Variability and Trends in the Vișeu River Runoff Regime. The classic hydrological water management dealt with the changing resources by assuming the existence of stationarity. Once stationarity is ...neglected in the design of hydraulic engineering, numerous errors and risk may exist in the operations and management strategies and will lead to unforeseen losses. Thus, one of the most important questions in today’s hydrology are: Did stationarity die? and if it is true How did stationarity die? As we know the climatic change is widely accepted so it is sad that by 2050 the effects of climate change may have a generally larger effect on flow regimes than it is estimated that dams and water withdrawals. If this is so, we must consideration that in this moment one of the most important aspect/moment is the change point identification in a period, from where significant change has occurred in a time series, for this we choose to use the Ms Excel Addinsoft XLStat to assess the homogeneity of the data by the Pettitt’s test, the von Neumann ratio test, the Buishand range test and also the standard normal homogeneity tests (SNHT). For the trend analysis we used the Mann-Kendall test and the classic linear regression test. Based on the results, we conclude that in case of the Vișeu watershed stationarity is questionable if not totally missing. As we see even if the precipitation values do not show significant changes regarding their homogeneity, the runoff series are changing, and in most cases this change is identified in the 20thcentury last decade. These results urge us to rethink and to reevaluate our sustainable water resource management for the future.
Variability and Trends in the Vișeu River Runoff Regime. The classic hydrological water management dealt with the changing resources by assuming the existence of stationarity. Once stationarity is ...neglected in the design of hydraulic engineering, numerous errors and risk may exist in the operations and management strategies and will lead to unforeseen losses. Thus, one of the most important questions in today’s hydrology are: Did stationarity die? and if it is true How did stationarity die? As we know the climatic change is widely accepted so it is sad that by 2050 the effects of climate change may have a generally larger effect on flow regimes than it is estimated that dams and water withdrawals. If this is so, we must consideration that in this moment one of the most important aspect/moment is the change point identification in a period, from where significant change has occurred in a time series, for this we choose to use the Ms Excel Addinsoft XLStat to assess the homogeneity of the data by the Pettitt’s test, the von Neumann ratio test, the Buishand range test and also the standard normal homogeneity tests (SNHT). For the trend analysis we used the Mann-Kendall test and the classic linear regression test. Based on the results, we conclude that in case of the Vișeu watershed stationarity is questionable if not totally missing. As we see even if the precipitation values do not show significant changes regarding their homogeneity, the runoff series are changing, and in most cases this change is identified in the 20thcentury last decade. These results urge us to rethink and to reevaluate our sustainable water resource management for the future.
Os eventos extremos de precipitação pluviométrica são frequentemente investigados por parte da comunidade científica devido aos prejuízos socioeconômicos causados pelo excesso ou escassez de chuvas ...em determinadas regiões do mundo. No Nordeste brasileiro, diversos problemas como migrações, fome e mortes têm relação com as recorrentes secas que, historicamente, assolam a região. Ainda assim, estudos sobre as variabilidades climáticas no Semiárido são escassos e generalistas, sobretudo aqueles onde se busca investigar possíveis relações com as mudanças climáticas globais, uma das maiores ameaças do presente século. Deste modo, a presente pesquisa objetiva analisar a tendência espaço-temporal de diferentes índices de precipitação pluviométrica na em uma região semiárida do estado de Pernambuco e a influência da Temperatura de Superfície do Mar (TSM) dos Oceanos Pacífico e Atlântico na variabilidade pluviométrica da região. Foram calculados nove índices climáticos de precipitação relativos à intensidade diária, DCS, DCC e PRCPTOT com a utilização dos softwares Rclimdex e Climap. O teste Mann-Kendall (MK) foi aplicado neste estudo para detectar possíveis alterações de ordem climática das séries temporais de precipitação. Os índices climáticos foram correlacionados com dados da Temperatura da Superfície do Mar (TSM) dos oceanos Pacífico e Atlântico. Verificou-se significativa variação espacial dos sinais de tendência e nível de significância estatística, indicando diminuição das chuvas na região estudada. Constatou-se que as precipitações com tendências negativas são influenciadas pelas variações da TSM nos oceanos Pacífico e Atlântico, evidenciando que o fenômeno El Niño influencia na redução das chuvas na região, assim como o Dipolo do Atlântico.
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