Trends and variability in extreme precipitation indices over Maghreb countries

Abstract

Abstract. Maghreb countries are highly vulnerable to extreme hydrological events, such as floods and droughts, driven by the strong variability of precipitation. While several studies have analyzed the presence of trends in precipitation records for the Euro-Mediterranean basin, this study provides a regional assessment of trends on its southernmost shores. A database of 22 stations located in Algeria, Morocco and Tunisia with between 33 and 59 yr of daily precipitation records is considered. The change points and trends are analyzed for eleven climate indices, describing several features of the precipitation regime. The issue of conducting multiple hypothesis tests is addressed through the implementation of a false discovery rate procedure. The spatial and interannual variability of the precipitation indices at the different stations are analyzed and compared with largescale atmospheric circulation patterns, including the North Atlantic Oscillation (NAO), western Mediterranean Oscillation (WEMO), Mediterranean Oscillation (MO) and El Niño-Southern Oscillation (ENSO). Results show a strong tendency towards a decrease of precipitation totals and wet days together with an increase in the duration of dry periods, mainly for Morocco and western Algeria. On the other hand, only a few significant trends are detected for heavy precipitation indices. The NAO and MO patterns are well correlated with precipitation indices describing precipitation amounts, the number of dry days and the length of wet and dry periods, whereas heavy precipitation indices exhibit a strong spatial variability and are only moderately correlated with large-scale atmospheric circulation patterns.

Recent changes in climate, hydrology and sediment load in the Wadi Abd, Algeria (1970–2010)

“…Tramblay et al (2013) showed that the precipitation amounts and the number of dry days over the Maghreb were significantly correlated with the MO and NAO patterns. MO and NAO showed positive trends from the 1970s onwards which could explain the trend towards decreasing frontal conditions over the Mediterranean basin and thus increasing droughts.…”

Evolution des pluies extrêmes dans le bassin du Chéliff (Algérie) au cours des 40 dernières années 1971–2010

“…Cette méthode a été déjà utilisée par plusieurs auteurs (Maheras et al, 2008;Sahani et al, 2012;Ozer et al, 2007;Lupikasza, 2008;Martinez et al, 2007). Le test de Mann-Kendall permet de déceler l'existence d'une tendance globale au sein d'une série de données temporelles et a déjà été utilisé pour la détection de tendance dans les séries pluviométriques et tester leur significativité (Vannitsem et al, 1991;Norrant et Douguédroit, 2004;Maheras et al, 2008;Chaouche et al, 2010;Tramblay et al, 2013;Driouch et al, 2010).…”

“…Les stations de Sidi Medjahed et Kenenda sont seules à montrer une baisse significative de P90 de 1,7 jour par décennie. Ces résultats coïncident avec ceux trouvés par Tramblay et al (2013) au Maghreb et d'autres auteurs en Méditerranée (Kioutsioukis et al, 2010;Norrant et Douguédroit, 2006;Brunetti et al, 2001). L'indice de l'intensité journalière (SDII) montre une tendance générale à la baisse plutôt significative aux stations de Mehdia, Derrag, Zoubiria et Sidi Medjahed qui varie entre 0,4 et 0,7 mm jr −1 par décennie.…”

Links between circulation indices and precipitation in the Mediterranean in an ensemble of regional climate models

“…At the global scale, the Mediterranean region is possibly one of the most vulnerable regions to climate change because of the combination of drying and warming (Rosenzweig et al 2007; Giorgi and Lionello 2008). Analyses of the past 50 years of precipitation records in the rainy season have revealed decreasing trends in most Mediterranean regions, the exception being the northeastern Africa and the western Iberian Peninsula (Feidas et al 2007;Philandras et al 2011;Tramblay et al 2013). Projections by global and regional climate model simulations show that the decrease of winter precipitation in the European part of the Mediterranean is likely to continue during the twenty-first century (Giorgi and Lionello 2008;Hertig et al 2013).…”