Variabilidade das ondas de calor na região subtropical do Brasil

Abstract

Recently, much has been discussed in the scientific community about global warming since the 1970s and its impacts on temperature extremes. Some studies refer to a time of the 21st century. However, even if this gap is confirmed, results in the literature point to an increase in the frequency, intensity and persistence of the extremes in this same period. In addition to anthropogenic activities, climatic differences may be controlling these slower and faster periods of heating. Considering the impacts that extremes of temperature can cause, both for society and the economy, this work aims to analyze the variability of heat waves in the subtropical region of Brazil from 1980 to 2013. That is, verify how these extremes are behaving over the decades, and relate them to the South Atlantic Convergence Zone and the Antarctic Oscillation. For this, daily data of maximum temperature and geopotential height in high and low levels were used, as well as the SACZ events from 1992 to 2013. Through the applied methodology, the subtropical region was divided in two (regions 1 and 2). For both, there has been an increase in the frequency, intensity and persistence of heat waves since the 80's. In addition, the events presented a seasonal characteristic, more frequently in the winter period. Regarding the SACZ, it is clear the influence of the same on the temperature anomalies in the region more to the south of its climatological position, however there were few extremes of temperature during the period that the SACZ acts. The Antarctic Oscillation also presented an important relation with the statistical characteristics of the heat waves. The events were more frequent and persistent during AAO-, whereas in AAO + they were more intense. The behavior of the atmosphere during the heat waves in each of the phases was also analyzed. The two regions presented similar behavior, being that in the negative phase the heat waves are favored by the action of an atmospheric blockade in the Southeast Pacific together with the positive anomalies on the Atlantic, while in the positive phase the South Atlantic positive anomalies plays a dominant role in the development of heat waves. This pattern repeats at high and low levels, showing that the systems are vertically aligned.