Temperature extremes in the south of South America in relation to Atlantic Ocean surface temperature and Southern Hemisphere circulation

BARRUCAND MARIANA; RUSTICUCCI MATILDE; VARGAS WALTER

JOURNAL OF GEOPHYSICAL RESEARCH

American Geophysical Union

Año: 2008

0148-0227

The objective of this research is to study the main variability modes of the4 frequency of extreme temperatures in the south of South America, their relation to the sea5 surface temperatures and some indices of atmospheric circulation in the Southern6 Hemisphere. Observational data and reanalysis data were used for this propose over the7 1964-2003 period. An initial analysis showed that between the months of March and June8 the frequency of warm events (especially warm nights) are highly associated with the sea9 surface temperature in coastal zones. A wavelet analysis showed that the main variability10 mode found at a seasonal scale was an 8-year wave signal present in spring that remains11 active until the 90’s. It was noticeable in the analysis of cold nights, Atlantic SSTs, Pacific12 SSTs and the Southern Annular Mode (SAM). A cross-wavelet analysis among them13 reflected this signal as a common variability mode, with the positive phase of the SAM14 congruent with warmest condition in the coastal zones of the Atlantic Ocean and lower15 cases of cold nights at the reference meteorological stations analyzed. Although longer16 series are desirable for low frequency variability analysis, the results agree with previous17 studies that take into account an 8-year periodicity of the baroclinic waves at the Southern18 Hemisphere, supporting the relevance of the 8-year signal19