Influência dos fenômenos ENOS na ocorrência de frentes frias no litoral sul do Brasil

The climatologic phenomena of large-scale El Niño and La Niñaare associated with variations in surface temperature of the Pacific Ocean.In the southern Brazil, they are responsible for changing the patterns ofoccurrence and intensity of frontal systems and the events was analyzed tounderstand theirs effects. Three periods were analyzed: June 2004 to May2005, June 2007 to May 2008 and June 2005 to May 2006. These periodscorrespond to El Niño, La Niña and neutral period, respectively. The frontsystem analysis was made using synoptic maps of the Centro de Previsãodo Tempo e Estudos Climáticos (CPTEC). The fronts were counted andclassified according to their intensity, and the linear correlations wereperformed between an index of intensity of ENSO, provided by theNational Oceanic Atmospheric Administration (NOAA), and the intensityof fronts. The results were seasonally grouped. During the El Niñohappened a decrease in the amount of cold fronts at the region in all seasons(autumn excepted), and the biggest difference occurred in the summer(there was 4 fronts in El Niño period and 14 in neutral period). In La Niñaperiod, there was an increase of the number of cold fronts in all seasons,especially in winter (18 front systems); at neutral period occurred 11 frontsystems. However, the intensity of cold fronts was not affected by thephenomenon, except in October. Therefore, the climate of the region insouthern Brazil is influenced by both direct ENSO phenomena analyzedand this is conditioned by the intensity that they present themselves.