CONICET | Buscador de Institutos y Recursos Humanos

We explore the occurrence of intraseasonal summer heat waves in southeastern Patagonia (SEPG, 46∘?52∘S;65∘?70∘W) since the late 19th century by means of the Twentieth Century Reanalysis version 2 (20CRv2). In total, we identify201 cases for 1872?2010 using criteria of intensity and persistence. In SEPG, the corresponding intraseasonal temperaturesignals are centred around the first day of each cluster of days fulfilling those conditions (named day 0). The mean warmdeviation lasts for approximately 2weeks and exhibits a mean temperature peak of 4.3 ∘C on day 0 (the warmest day in themean signal). In a regional context, the mean temperature perturbation associated with these heat waves affects a broad area onboth sides of the Andes. The warming in SEPG is caused by temperature advection and enhanced radiative heating, followinga high pressure system over southern South America (SSA). This atmospheric perturbation is embedded in a wave-train-likepattern along the South Pacific.As part of this pattern, a cyclonic anomaly progresses eastward over the Tasman Sea inOceania,moving from southeastern Australia (day −6, causing a dry anomaly there) over New Zealand (day −3, inducing a wet anomalyon its Southern Island). The anomalous circulation triggered by the wave train leads thus to a teleconnection between SSAand Oceania, documented in a previous work for the interannual scale. Two thirds of the heat wave events are linked toenhanced ascent in the South Atlantic Convergence Zone (SACZ) and around one third of the events within 1957?2010 areassociated with extreme absolute maximum temperatures observed at a station-based record from SEPG. Finally, possiblespatial modulations of the wave train pattern at the interannual and interdecadal timescales are discussed.

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