Wavelet Analysis of Rainfall and Runoff Multidecadal Time Series on Large River Basins in Western North Africa

Abstract

This work is dedicated to the study of the spatio-temporal variability of climate in Morocco by the analysis of rainfall (gridded and gauged data) and runoff. The wavelet analysis method has been used in this study to compare the rainfall and runoff series and to show the major discontinuities identified in 1970, 1980, and 2000. Several modes of variability have been detected; this approach has been applied to show annual (1 year) and inter-annual modes (2–4 years, 4–8 years, 8–12/8–16 years, and 16–30 years), and some modes are specific to some stations. This analysis will be complemented by the gridded data covering the period from 1940 to 1999, which will allow for a better understanding of the spatial variability of the highlighted signals set, which identified frequencies at 1 year and 8–16 years, distinguished different time periods at each basin and identified three main discontinuities in 1970, 1980, and 2000. The contribution of climatic indices is important as it is between 55% and 80%.

Spatiotemporal evolution of droughts and their teleconnections with large-scale climatic indices in the Lower Sebou Basin in northwestern Morocco

“…The distribution and characteristics of these stations are presented in Figure 1 and Table 1. Two important large-scale climate anomalies were selected to analyse the main drivers of drought in the LSB: NAO (North Atlantic Oscillation) and MO (Mediterranean Oscillation) (Zamrane, Mahé and Laftouhi 2021). The NAO is called a meridional dipole of atmospheric pressure with centres of action near the Azores (37 °N, -25 °E) and Iceland (65 °N, -18 °E) (Figure 2).…”

“…Wavelet coherence is an approach used for analysing the degree of coherence of cross wavelet transform in time-frequency space. It has been widely used to analyse the periodicity of drought and the relationships between hydrological variability and possible teleconnections (Zamrane, Mahé and Laftouhi 2021).…”

“…The spatio-temporal evolution of droughts in the LSB is controlled by landscape heterogeneity and specific climatic events such as extreme weather anomalies and large-scale atmospheric circulations (Lamb and Peppler 1987;Zamrane, Mahé and Laftouhi 2021;Hakam et al 2022b). Some studies have demonstrated an anti-correlation of rainfall in Morocco, especially in the northwestern part, and the North Atlantic Oscillation (NAO) (Marchane et al 2016;Driouech et al 2021).…”

Selection of Optimal Palmer Predictors for Increasing the Predictability of the Danube Discharge: New Findings Based on Information Theory and Partial Wavelet Coherence Analysis

“…Zamrane et al [ 88 ] also applied wavelet analysis, in which certain modes of climate variability between rainfall and runoff for northwest Africa area were found.…”

Time-Series Analysis of Isotope Composition of Precipitation in Zagreb, Croatia

“…Most of the WA were used to study global long-term periods [2][3][4][5][6][7]. Some were used to teleconnect large-scale climate indices and hydrochemical and isotopic characteristics of a karst spring [8] or to study spatio-temporal variability of rainfall and streamflows over the last decades [9].…”