Variabilidade da chuva e desastres associados à dinâmica hidroclimática no estado do Maranhão

Abstract

The objective of this research is to analyze the spatial and temporal variability of rainfall and the disasters associated with hydroclimatic dynamics in the state of Maranhão. As a methodological guide, the theoretical framework was initially elaborated, later, the validation of estimated rainfall data from the CHIRPS was carried out, using the Person correlation with annual data from INMET meteorological stations in the state, after this analysis was used. if the multivariate statistical techniques of Principal Component Analysis (PCA) to identify the spatial and temporal pattern of rainfall and the Cluster Analysis to define the Homogeneous Rainfall Regions (RPH). In order to identify the repercussions related to hydroclimatic dynamics, the decrees published in the federal scope of emergency situations and states of calamity for drought, inundation/floods, flash floods and flooding were used, in addition to calculating the Rainfall Anomaly Index by municipality, seeking to characterize the spatial variability of rainfall and compare it with the federal recognition of disasters. As a result, significant correlations were obtained in the monthly CHIRPS data. In the Principal Components Analysis, it was possible to identify two spatial and temporal patterns of rainfall in the state, one characterizing the central-northern portion of the state, with rains concentrated in the first half of the year, and a second that defines the central-south portion, with a regime of rains that already starts in the months of October and November. The cluster analysis made it possible to divide the state into five Homogeneous Rainfall Regions (RPH), with RPH 1 having the highest volumes of rainfall, RPH 4 having the lowest volume of rainfall and RPH 5 being different from the others by starting the rainy season in October. In the analysis of rainfall variability (1989 to 2020), the years 1989, 2009 and 2020 were the wettest years and had the highest number of municipalities with IAC considered extremely rainy, while the years 1992 and 2012 were the driest, with a greater number of municipalities with extremely dry IAC. It was also identified that the Atlantic Sea Surface Temperatures have a greater influence on the definition of the rainfall regime in the state of Maranhão, and that when the Positive Dipole and El Niño occur simultaneously, there is a considerable decrease in rainfall and, consequently, a greater number of disaster decrees. related to drought. The largest number of decrees is related to drought, followed by inundation/floods. The droughts are located, especially in municipalities of RPH 3 and 4. While the floods/floods are located in RPH 2. Finally, the use of estimated data from CHIRPS proved to be a good option for rainfall analysis in the absence of surface data, the statistical techniques used allowed inferring about the spatial and temporal variability of rainfall and the comparative analysis of the IAC with the repercussions of hydroclimatic events made it possible to prove the influence of climate dynamics in geographic space.