Variabilidad intraestacional de las condiciones níveas en los Andes Centrales relacionadas con los cambios en el régimen hidrológico del río Atuel

Abstract

“Intraseasonal variability of the snow conditions in the Central Andes related to changes in the hydrological regime of the Atuel river”. By means of the principal compo- nent analysis applied to the Río Atuel hydrological annual cycle, the main modes of intra-sea- sonal variability of the river surface runoff are studied. The relationships between principal components (PCs) and the local variability of precipitation and temperature in the basin, and the associated global atmospheric circulation are analyzed. The third principal component (PC 3) represents the alternation of streamflow anomalies between Oct.-Nov., Nov.-Dec., Dec.- Jan. and Jan.-Feb.; and it accounts for 9.7% of the total variance. On the other hand, the PC 4 represents the alternation of anomalies of the runoffs between November, January and February; accounting for 7.5% of the total variance. These components explain more than half (58%) of the intra-seasonal variability of the river streamflows, and stand for 17.2% of the total. Both PC 3 and 4 patterns are linked to the intra-seasonal variability of temperature anom- alies over the basin region. This variability acts promoting or inhibiting the melting winter snow and consequent abnormal increase or decrease in river flows, respectively. In turn, these temperature anomalies are associated with pressure anomalies in height and/or low levels, largely related to Rossby wave trains that extend along the South Pacific and South America.