This paper is an observational study of the precipitation events in Pelotas city, associated with synoptic systems and processes during nine months of each of the following years: La Niña, El Niño and Normal. The synoptic systems found in this study are: the frontal zones (cold, warm, occluded, secondary and stationary fronts) and the cyclogenesis processes. The precipitations inside the air masses were associated with Cb and St clouds and with mesoscale convective complexes (MCC). The precipitation values (total-TMP and average-AP, per month) produced by the different synoptic systems were calculated and the mensal variations of these values were analysed. The highest precipitations frequencies associated with cold and warm fronts, waves and cyclogenetic cloudiness were detected in the El Niño year. The precipitations caused by occluded and secondary fronts were more frequent in the La Niña year. Very heavy precipitations associated with cold and occluded fronts, waves and cold front extremities were found more frequently during the El Niño year. The greatest TMP values were produced by occluded fronts and by young cyclones in the El Niño year.
La Niña and El Niño years; precipitation; synoptic systems and processes
