The use of hybrid methods for change points and trends detection in rainfall series of northern Algeria
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RESEARCH ARTICLE - HYDROLOGY
The use of hybrid methods for change points and trends detection in rainfall series of northern Algeria Bilel Zerouali1 · Mohamed Chettih1 · Zaki Abda1 · Mohamed Mesbah2 · Mohammed Djemai3 Received: 4 February 2020 / Accepted: 29 July 2020 © Institute of Geophysics, Polish Academy of Sciences & Polish Academy of Sciences 2020
Abstract The aim of this research is to assess relatively new hybrid methods for changes points and trends detection on rainfall series: Dynamic Programming Bayesian Change Point Approach (BA), Şen’s innovative trend method (ITM) and its double (D-ITM) and triple (T-ITM) version using the multi-scale analysis of the discrete wavelet transform (DWT) as a coupling method. Three representatives rainfall stations of northern Algeria were analysed at annual scale during the period 1920–2011. Moreover, correlation and spectral analysis (CSA) was applied for periodicity analysis. The CSA indicates the dominance of interannual to multidecadal rainfall periodicity fluctuations (2-years, 5-years and 20-years) characterising long term structured processes. Moreover, an abrupt downward trend with significant probability was detected from the 1970s with a relatively wet period between the periods 1950–1970 and 2001–2011. The latter is observed in particular in the central and eastern stations, well-explained by the BA-DWT. The results showed that the comparison results from different modelling approaches found that the hybrid models (BA-DWT, ITM-DWT, D-ITM-DWT, T-ITM-DWT) often perform better than the conventional approach (BA, ITM, D-ITM, T-ITM), where the computation time is very reasonable. The analysis revealed that information stemming from discrete wavelet spectrums significantly increased the accuracy of the methods for detecting hidden change points and trends. Keywords Changes points · Trends · Hybrid methods · Discrete wavelet transform · Algeria
Introduction Precipitation is the ultimate source of water resources and a key element in climate characterization at a particular location. From the beginning of the twentieth century and based on negative human impacts on environment, the characteristics of precipitation on a global level have been marked by a significant change on a spatial and temporal scale (Hallouz * Bilel Zerouali b.zerouali@lagh‑univ.dz 1
Research Laboratory of Water Resources, Soil and Environment, Department of Civil Engineering, Faculty of Civil Engineering and Architecture, Amar Telidji University, P. O. Box 37.G, 03000 Laghouat, Algeria
2
LGBO, Laboratory, Earth Sciences Faculty, University of Science and Technology Houari Boumediene, BP 32, 16311 Bab Ezzouar, Algeria
3
LGEA, Laboratory of Geomaterials, Environment and Development, Department of Civil Engineering, Mouloud Mammeri University, BP no 10.RP, Hasnaoua, Tizi‑Ouzou, Algeria
et al. 2020; Oroud 2018; Rashid and Beecham 2019; Mrad et al. 2019; Pandey et al. 2017; Almazroui et al. 2018; Santos et al. 2018; Spinoni et al. 2018; Zerouali et al. 2018; Partal 2017; Chakrabo
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