Análise das causas climáticas sobre os núcleos de desertificação brasileiros

Abstract

Desertification is a process of degrading soil modification, leading to desert aspects, as a result of climatic variations and/or human activities. This study has the general objective of studying the possible climatic causes that influence the degradation process in the existing desertification nuclei in Brazil. Rainfall and temperature data from the cities that make up the Desertification Nuclei in Brazil were used, from the National Water Agency, the National Institute of Meteorology and the Ceará Foundation for Meteorology and Water Resources for the period from 1981 to 2020 for Irauçuba, 1961 to 2019 for Cabrobó, 1971 to 2019 for Gilbués and 1989 to 2019 for Seridó. Data from the Atlantic Dipole, Southern Oscillation Index, Pacific Interdecadal Oscillation, Pacific Decennial Oscillation and Atlantic Multidecennial Oscillation obtained from the Earth System Research Laboratory/National Oceanic and Atmospheric Administration were also used. It was observed that the frequency of dry years was greater than that of wet years, according to the Rain Anomaly Index (IAC) in Irauçuba, the year 2000 became a point of inversion in the distribution of local rainfall. For Cabrobó and Seridó, the IAC recorded more occurrences of wet years than dry years, however, dry events were more frequent and more intense, and in some of these years there was an El Niño phenomenon. In the center of Gilbués, dry and wet years occurred practically in the same proportion. Decreasing trends were detected in the precipitation of the cores indicating that the rains decreased over time, while in the temperature series an increasing trend was pointed out. The Ondaleta analyzes showed the influence of different temporal scales on the series of precipitation and temperature of the nuclei, being these scales responsible for anomalous increases in the series, when acting simultaneously. The time scales that most influence the Irauçuba precipitation series are: the seasonal scale, the 4 to 8 year scale and the 11 year scale. Cabrobó was influenced by the seasonal scale, the scale of 2 to 4 years, the scale of 11 years. The Seridó precipitation series is influenced by the seasonal scale, from 2 to 4 years and from 7 years. The presence of the seasonal scale was observed in the precipitation series of Gilbués, the time scale of 2 to 4 years, coinciding with the period of action of the scale of 11 and the scale of 16 years. The cross wavelet showed interrelationships between the precipitation series of the cores and the series of climatic indices of the dominant scales of each core. The maximum precipitation in the Irauçuba core occurs 3 years before the maximum occurrence of the Atlantic Dipole. For Cabrobó, the maximum precipitation occurs 27 to 54 months before the maximum of the Atlantic Dipole. In Seridó the maximum precipitation occurs 33 months after the maximum of the IOS. For Gilbués, the coherence suggests that the maximum peak of precipitation in the locality occurs 72 months before the maximum of the Atlantic Dipole. Thus revealing that the relationship between the climatic phenomena and the series of precipitation can contribute to the climate forecast for the Desertification Nuclei.