Isotopic composition of precipitation in the Mediterranean Basin in relation to air circulation patterns and climate

Two stations of rainfall sampling and measurements of meteorological parameters were used in this study. The first one, located in Algiers, is under Mediterranean climatic influence. The second one, located in the Ahaggar massif, in the middle of Sahara desert, is subject to the extreme inflow of African western monsoon. In Algiers, the mean isotopic contents of precipitation [δO= -5‰; δ H= -28‰ vs VSMOW], define a meteoric water line of slope 7.1, in conformity with what is known in similar climatic situation. The deuterium excess is 11.4‰. In Assekrem, the isotopic results of period 2000/2004, indicate relatively enriched values δO=-0.2‰; δH= +8‰), compared to the normal. This is due to the preponderance of the summer rains (hot season) compared to the rains of the fresh season (autumn and winter). The oxygen / deuterium relationship presents a slope of 5.05, typical of evaporating line. The mean value of deuterium excess is 1.6‰. The strong isotopic signal in precipitation associated with Inter Tropical Convergence Zone (ITCZ) displacement represents an excellent methodology for a correct reconstruction of the current atmospheric circulation and climatic changes suffered by the region.