Análise de ondas de calor e de frio no Rio Grande do Sul por diferentes métodos.

Abstract

In order to identify and analyze the heat and cold waves that occur in Rio Grande do Sul four different procedures were used in 13 meteorological stations, spatially distributed in the State, between 1961 and 2010. Heat waves were considered and periods of five or more consecutive days of positive and negative anomalies of maximum and minimum temperatures, respectively. The annual, seasonal and daily maximum and minimum climatic averages were calculated, followed by the number of heat and cold waves for each locality, annual and seasonal, using the World Meteorological Organization (IOMM), Daily Index (ID), Seasonal Index (IS) and RClimdex. When comparing the methods it was verified that the IOMM was the one that detected the greatest number of events, the ID and IS methods practically did not detect heat waves in summer and cold in the winter and RClimdex was unable to detect the internal variability of heat and cold waves in Rio Grande do Sul. Regarding the spatial configurations of the climatological means of the maximum and minimum air temperatures during the days of heat and cold waves, respectively, as well as the number of days of heat waves and cold it was observed a gradient of the coast inland and from southeast to northwest. In some ways these settings are a response to the effects of continental, latitude and relief. As for the association of the influence of the El Niño and La Niña events on the number of heat and cold waves, it was observed that, on average, a larger number of heat waves occur in the El Niño and cold years in La Niña, however, this relationship is not statistically significant. Therefore, it is not possible to state categorically that in El Niño years there is a greater number of heat waves and that of La Niña of cold.