Atmospheric circulation features associated with the discharge of the Atuel (Cuyo) and Chubut (Northern Patagonia) rivers in the southern Andes

ARANEO D.

Tilcara, Jujuy

Encuentro; International Meeting IAI CRN 2047: Documenting, understanding and projecting changes in the hydrological cycle in the American Cordillera.; 2011

Inter American Institute for Global Change Research

The Argentinean Andean rivers of Cuyo (28º S to 37º S) and northern Patagonia (NP) (37º S to 46º S) regions, show different hydrological regimes and their interannual runoff variability largely depends on winter atmospheric conditions. In this paper we analyze the different features of the winter tropospheric circulation patterns associated with the discharge variability observed in the Cuyo and NP rivers, using the Atuel and Chubut rivers as representative of both regions. The most important atmospheric low level (about 1000-850 hPa) conditions associated with high (low) Atuel discharges is the weakening (strengthening) of the mean atmospheric flow. For Chubut, the same atmospheric anomalies are observed, but displaced 5º southward.In the upper troposphere levels (about 500-200 hPa), our results suggest for Atuel river, the existence of a NW-SE direction wave pattern extending from Australia to the South Atlantic. This pattern favors positive (negative) pressure anomalies west of the Drake Passage, which deflect the storm tracks northward (southward) and hence increase (decrease) precipitation that subsequently controls the Atuel discharges. In contrast, the Chubut discharges are mainly controlled by a shorter wave pattern along the subtropical Pacific, which extends zonally across South America. This pattern helps to maintain low (high) pressure anomalies off the Chilean coast at the latitude of the upper-Chubut river basin that are linked with high (low) Chubut runoff.