Impacto del fenómeno ENOS en el régimen hidrometeorológico de Mendoza, Argentina

The main purpose of this work is to analyze the hydroclimatological effects that El Niño event causes in the Argentinean Province of Mendoza. Secondary objectives of this study are to consider prevailing meteorological conditions (most frequent synoptic conditions) during winter both in the plains and in the mountain range area. The study area has been hydrologically and meteorologically characterized by using monthly stream flow from the most important rivers in the region as well as using synoptic climalogical data. The study comprises the ENSO warm events registered during this century, emphasizing the 1982-1983, 1986-1987, 1991-1993, and the first evidences of the 1997-1998 events. The main results show a substantial increase in summer river flows just after the winter precipitation excess produced by the corresponding warm ENSO event. The maximum-year value associated to the 1982-1983 warm event, considered until 1997 as the most severe El Niño event in this century, is emphasized as the absolute maximum of the discharge series. The most severe precipitations in the mountain range obey a most frequent passage of low-pressure centers and long wave troughs in lower latitudes than normal. This determines a negative anomaly in the pressure field both in the surface as in the mid altitude atmosphere.