ABSTRACT:The potential impact of large-scale climate patterns of El Niño Southern Oscillation (ENSO), North Atlantic Oscillation (NAO) and Pacific Decadal Oscillation (PDO) in modulating precipitation regimes across the upper Medjerda River Basin in northern Tunisia is assessed. As the case study is located in the Mediterranean region (North Africa), the regional Mediterranean Oscillation (MOAC) and Western Mediterranean Oscillation (WeMO) are also investigated. Six precipitation time series are also observed. Strong correlations are identified between ENSO and precipitation series at lag −2 years. Extreme ENSO years are reflected in the precipitation as periods of severe water deficit or excess. Wavelet spectra driven to seasonal precipitation reveal that precipitation is organized in preferred bands with distinct activities in each scale band, and that most of the precipitation variance is explained by the 2-8-year scales. Using cross-wavelet analysis, climate patterns that are most associated with precipitation variability are identified. The analysis demonstrates also that precipitations are simultaneously controlled by different climate patterns. Particularly, the influence of ENSO on precipitation is stronger as well as that of PDO and MO. Results indicate that precipitation variability at the upper Medjerda River Basin is associated with global-scale ENSO processes at the annual as well as seasonal time scales and is aligned with changing phase difference between periods. Moreover, separation of annual precipitation into two seasons reveals statistically significant associations between El Niño and La Niña phases of ENSO with dry and wet seasonal precipitation, respectively. Complementing this, three streamflow records with length up to 104 years are used, and relationships with rainfall series are analysed using wavelets. A strong coherence between rainfall and streamflow observations is found and justifies undertaking the study of climate-streamflow relationships where ENSO exhibits potential impacts on annual streamflows.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.