Veranicos no Rio Grande do Sul - Nova metodologia para quantificação de eventos Veranicos at Rio Grande do Sul - new methodology for quantification of events

Despite the region where Rio Grande do Sul is located having well defined seasons, during winter the region may show, for some days, anomalous pattern related to the values of temperature (daily maximum and minimum) and precipitation (drought), being known as periods of veranico, portuguese word meaning “little summer”. This study shows a new methodology approaching climatological values to describe thresholds for determination of veranicos at each location and, thus, removing local or topographic influences. Data of 11 meteorological stations operated by INMET were used for the period from 1961-2011 to determine the thresholds and identify the veranicos. It can be seen that the veranicos present their maximum towards west-northwest of the state with a minimum at the seaside region and extreme north of the state. At the synoptic study of the veranico occurrence, it can be seen a classic pattern of atmospheric blocking acting over the region and contributing to the occurrence of the veranico.