The influence of general circulation patterns on humid and dry years in the cuyo andean region of argentina

Due to the population growth in the agricultural areas under irrigation in Cuyo (West Central Argentina), the consequences of fluctuations in cordillerean river regimes, whose snowfalls provide water for irrigation, have begun to be felt acutely in recent years. Hemispheric and regional circulation patterns associated with two extreme hydrological (drought and excess) situations in Cuyo were investigated, searching for links between both scales. Important anomalies of hemispheric and regional occurrences have been observed when droughts and floods occur at the regional scale (upper level of the mountain range central Andes and Chilean Mediterranean zone). Precipitation fluctuations show a direct or inverse association with other South American Regions (Uruguay and Islas Orcadas del Sur) and also an important teleconnection between phenomena of extratropical latitudes. The anomalous monthly average pressure fields (regional scale) are generated by an increase (20 to 30 per cent over the normal frequency) of a few persistent synoptic models, and by a westerly wave with ridge or trough over Islas Orcadas del Sur (South Orkneys Is.) or towards the west of Juan Fernández.