Data Analysis to Detect Inhomogeneity, Change Points, Trends in Observations: An Application to Po River Discharge Extremes

Vezzoli, Renata; Pecora, Silvano; Zenoni, Enrica; Tonelli, Fabrizio

doi:10.2139/ssrn.2195345

Cited by 21 publications

(13 citation statements)

References 24 publications

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“…Standard Normal Homogeneity Test (SNHT) developed by Alexandersson (1986) has been used frequently by the researcher for the detection of change point years (break points) and for inhomogeneity check in hydro-climatic time series, as in (Jaiswal et al, 2015;Vezzoli et al, 2012;Štěpánek, 2009;Freiwan and Kadioǧlu, 2008;Göktürk et al, 2008).…”

Section: Standard Normal Homogeneity Testmentioning

confidence: 99%

Analysis of causes of decreasing inflow to the Lake Chad due to climate variability and human activities

Mahmood

Jia

2018

Preprint

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Abstract. In the 1960s, Lake Chad was the world’s sixth largest water body, which has since shrunk dramatically from a surface area of 25,000 km2 to only 2,000 km2 in the following 40 years. In the present study, hydro-climatic variability in the Chari-Logone, Komadugu-Yobe, YENG (Yedseram, El-Beid, Ngadda and Gubio basins) as well as Lake Fitri basins and decreasing streamflow to Lake Chad due to climate variability and human activities were separated and quantified using trend analysis, change point analysis, and hydrological approach, for the period of 1951–2015. The results showed very strong signals (α = 0.001) of increasing trend in mean temperature, with an average increase of 1.4 °C, and very weak (α = 0.1) to strong (α = 0.01) decreasing signals in precipitation, with an average decrease of 15 %. In case of streamflow to Lake Chad, very strong decreasing trends were observed, showing 67 % reduction for the whole period. The north-eastern parts were most affected parts in case of increasing temperature and decreasing precipitation. Decreasing flow due to both climate variability and human activities were ranged from 34 % to 45 % in different decades, from 1972 to 2013. On the whole, a 66 % of total decline in streamflow was observed due to human activities and 34 % due to climate variability. Most reduction in streamflow (59 %) due to climate variability was explored only during 1982–1991 because a devastating drought was occurred during this period. Since human activities caused most reduction in streamflow to Lake Chad than climate, inflow to the lake can be improved by reducing or properly managing the human activities and using sustainable water resources management.

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Section: Standard Normal Homogeneity Testmentioning

confidence: 99%

Analysis of causes of decreasing inflow to the Lake Chad due to climate variability and human activities

Mahmood

Jia

2018

Preprint

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“…The computed value of R= ffiffi ffi n p is compared with critical values given by Buishand (1982) and Winingaard et al (2003) and has been used for detection of possible change (Table 2). (Alexandersson 1986) The test statistic (T k ) is used to compare the mean of first n observations with the mean of the remaining (n-k) observations with n data points (Stepanek et al 2009;Vezzoli at al. 2012).…”

Section: Buishand's Range Testmentioning

confidence: 99%

Statistical Analysis for Change Detection and Trend Assessment in Climatological Parameters

2015

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Considering the importance of climatic variability on availability of water, irrigation demand, crop yield and other areas of life, an assessment of change detection and trend on monthly, seasonal and annual historical series of different climatic variables of Raipur, a capital city of newly created Chhattisgarh state of India, have been carried out. The change detection analysis has been conceded using Pettitt's test, von Neumann ratio test, Buishand's range test and standard normal homogeneity (SNH) test, while non-parametric tests including linear regression, Mann-Kendall and Spearman rho tests have been applied for trend analysis. The annual series of minimum temperature, wind speed, sunshine hour showed significant change points, while evaporation indicated a doubtful case and maximum temperature confirmed the homogeneity at 95 % confidence level. The change point analysis results of meteorological variables indicated different change points from year 1990 to 2000, with maximum change points in and around 1995. This was due to the industrialization and urbanization in this period as this city was selected as capital of Chhattisgarh state. Based on the results of change point analysis and development scenarios in and around Raipur city, trend analysis was applied for three different time periods namely: P-1 from 1971 to 1995, P-2 from 1986 to 2012, and P-3 the whole series from 1971 to 2012. The significant rising trend in the summer and rainy months in case of minimum temperature, and the winter months in case of maximum temperature during the periods P-2 and P-3 may affect water availability and water demands in the region. The relative humidity showed a significant rising trend in few summer and rainy months series of all three periods under investigation, while sunshine hours and evaporation indicated random distribution prior to 1995 (P-1), but a significant falling trend in few winter months and annual series during period P-3. Although the annual minimum, maximum temperatures and relative humidity showed a rising trend, the falling trend of pan evaporation

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“…Rainfall is the most adapted climate variable in order to accurately analyse and characterise the climate of an area [15,16] in addition to being the major input data into any hydrological system. Therefore, analysing rainfall data deserves the highest priority for improving water management by adapting strategies to climate change.…”

Section: Introductionmentioning

confidence: 99%

Analyzing Trend and Variability of Rainfall in The Tafna Basin (Northwestern Algeria)

et al. 2020

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Northwest Algeria has experienced fluctuations in rainfall between the two decades 1940s and 1990s from positive to negative anomalies, which reflected a significant decline in rainfall during the mid-1970s. Therefore, further analyzing rainfall in this region is required for improving the strategies on water resource management. In this study, we complement previous studies by dealing with sub basins that were not previously addressed in Tafna basin (our study area located in Northwest Algeria), and by including additional statistical methods (Kruskal–Wallis test, Jonckheere-Terpstra test, and the Friedman test) that were not earlier reported on the large scale (Northwest Algeria). In order to analyse the homogeneity, trends, and stationarity in rainfall time series for nine rainfall stations over the period 1979–2011, we have used several statistical tests. The results showed an increasing trend for annual rainfall after the break detected in 2007 for Djbel Chouachi, Ouled Mimoun, Sidi Benkhala stations using Hubert, Pettitt, and Buishand tests. The Lee and Heghinian test has detected a break at the same year in 2007 for all stations except Sebdou, Beni Bahdel, and Hennaya stations, which have a break date in 1980. We have confirmed this increasing trend for rainfall with other trend detection methods such as Mann Kendall and Sen’s method that highlighted an upward trend for all the stations in the autumn season, which is mainly due to an increase in rainfall in September and October. On a monthly scale, the date of rupture is different from one station to another because the time series are not homogeneous. In addition, we have applied three tests enabling further results: (i) the Jonckheere-Terpstra test has detected an upward trend for two stations (Khemis and Hennaya), (ii) Friedman test has indicated the difference between the mean rank again with Khemis and Hennaya stations and the Merbeh station, (iii) according to the Kruskal-Wallis test, there have been no variance detected between all the rainfall stations. The increasing trend in rainfall may lead to a rise in stream flow and enhance potential floods risks in low-lying regions of the study area.

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Data Analysis to Detect Inhomogeneity, Change Points, Trends in Observations: An Application to Po River Discharge Extremes

Cited by 21 publications

References 24 publications

Analysis of causes of decreasing inflow to the Lake Chad due to climate variability and human activities

Analysis of causes of decreasing inflow to the Lake Chad due to climate variability and human activities

Statistical Analysis for Change Detection and Trend Assessment in Climatological Parameters

Analyzing Trend and Variability of Rainfall in The Tafna Basin (Northwestern Algeria)

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