Abstract

TORRERO, Mariana P; AGOSTA, Eduardo A  and  ARANEO, Diego C. Características de la circulación troposférica asociada a las variaciones interanuales del caudal del río Tecka - Gualjaina, Argentina. Meteorologica [online]. 2016, vol.41, n.1, pp.3-19. ISSN 1850-468X.

The basin of the Tecka-Gualjaina River is located in the northwest of the Chubut Province, extended over an area of 5,318 km². The paper explores the influence of the atmosphere-ocean system on the interannual streamflow variability for the season of maximum streamflow (from June to November), which represents 80% of the annual streamflow, and of minimum streamflow (from December to May). The Hydric balance yielded dryness conditions, for which the temporal behavior of the streamflow depends on precipitation. The maximum streamflow series showed negative trend in the full available record 1956-2013, with a change in the regime of streamflow anomalies by the beginning of the 80s, evolving from a positive predominance before to a negative one after. The minimum streamflow series was more stationary, without significant trend. The dominant cycles in both time series are only observed in the interannual high frequency (~ 2 years and ~ 4-5 years). Teleconnections and forcing associated to the streamflow time series were analyzed in the period 1979-2013 using ERA-Interim reanalysis. The year-to-year variations of maximum streamflow time series were associated with low frequency (interannual) tropospheric teleconnection, symmetric about the equator, possibly associated with variations of tropical convection between about 10o N-10o S and 150o E -180o E, induced by variations of sea surface temperature in the equatorial western Pacific (180o W-150o W). The teleconnection affected the position and intensity of the subtropical and polar jets, altering the trajectory of winter baroclinic systems that precipitate in the region. The year-to-year variations of maximum streamflow time series were associated with a high latitude annular mode-like variability, modulated by a wave-3 train at mid-latitudes over the South Pacific and South Atlantic. These features might have favored dynamic changes in the extratropical moisture transport leading to changes in precipitation towards the mid-west and southern Patagonia, affecting the Tecka-Gualjaina River basin. The results showed that at least between 1979 and 2013, the Tecka-Gualjaina River streamflow variability had tropic-extratropical teleconnections as a main forcing, associated with variations in the warming of sea surface temperatures of the equatorial central Pacific, being partly due to ENSO activity.

Keywords : Tecka-Gualjaina River; Streamflow; Fluvial dynamics; Tropospheric teleconnection.

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