Variações e mecanismos atmosféricos de fundo que desencadeiam eventos simultâneos de seca e ondas de calor durante o verão sobre o Nordeste do Brasil

Abstract

Many studies have been carried out on heat waves and droughts in the northern hemisphere, but few studies have been presented for the southern hemisphere, especially in Brazil and almost no studies for the northeast, making an underdeveloped scenario regarding the mitigation of the effects of such events. The impacts generated by the combined effects of drought and heat waves reflect on the economy, agriculture and health, and may even lead to loss of human life. This work aimed to diagnose heat waves and drought events in terms of their frequency, duration and severity, as well as to investigate the phenomena that triggered simultaneous events of drought and heat waves during the period from 1961 to 2015. The methodology used in this study identifies hot flashes as a period of three or more consecutive days with daily maximum and minimum temperature above the 90th percentile, after being identified, the properties of intensity, duration (days) and frequency (number of hot flashes) were analyzed ). As for the SPI, it measures the excess or deficit of rainfall, accumulated in different time scales, in a given area. For this work, the SPI-3, SPI-6 and SPI-12 were used, where the simultaneous analysis of these events showed that the states of Bahia, Ceará and Piauí had the highest frequencies of heat waves, mainly in the year 2015, as well as extreme level drought. Similar meteorological patterns were found in different variables at the 850, 500 and 200 hPa levels. The results of the compositions suggest that the month of February was the most intense in the analyzed period, revealing maximum temperatures, positive anomalies and greater availability of moisture. The results for divergence showed anticyclonic circulation at low and medium levels, where the states of Pernambuco, Rio Grande do Norte, central region of Alagoas, Paraíba and northern Piauí showed negative intensity at low levels, at medium levels the negative intensity prevailed from the center from the hinterland towards Pernambuco. In the vorticity results, the negative intensity was more intense in the states of Bahia and Pernambuco.