The aim of this study was to characterize the rhythm of atmospheric systems in the northeast of São Paulo State, Brazil from the frequency of weather systems and types of polar outflows from the winter of 2008 to the fall of 2009. The circulation analysis was performed by the means of daily synoptic analysis of three isobaric levels: surface, 500 and 250 hPa. The results showed that there were 45 frontal passages mostly during one day, controlling 21.9% of the year. The most frequent intervals between two fronts were of 5 to 6 days, ranging from a minimum of 0 (with two fronts in the same day) to 18 days. Extratropical systems controlled most of the time (64.9% of year), with the anticyclonic systems acting in 43% of the year and the frontal ones, in 21.9%. The remaining time was controlled by tropical (Atlantic and Continental) systems (35.1%), being 31.8% by the Atlantic system and 3.3% by the Continental one. The period was dominated by oscillatory-type polar outflows (tending to interrupted) because of the high frequency of extratropical systems (64.9%), being a different year than the usual for this part of the state, where tropical and extratropical systems control equivalent periods of the year (50% for tropical and 50% for extratropical).
São Paulo State; Atmospheric circulation; Frequency
