Tendências, agrupamentos e índices padronizado e de anomalia: uma análise da precipitação pluviométrica no Rio Grande do Sul

Abstract

Changes in climate variables affect all stages of agricultural activities, and the rainfall regime have the strongest effect on environmental conditions and consequently, causing the greatest direct effect on the crop production. Therefore, over the last decades, statistical methods have been developed, improved and used as tools to understand the characteristics and duration of rainy and drought periods, enabling their understanding especially in places where the economy is directly and/or indirectly linked to agriculture. Therefore, the study aim was to analyze the rainfall exclusion variability in the state of Rio Grande do Sul, through monthly data from 23 weather stations, between 1980 and 2019. The specific objectives were: (a) Quantify rainfall differentiation in different physiographic regions of Rio Grande do Sul, verifying its seasonal distribution and trends in annual and seasonal series; (b) Determine homogeneous protection groups for Rio Grande do Sul, through principal component analysis (PCA) and application of Ward's hierarchical method; and (c) Evaluate the periods of drought and of lower dryland soybean yields in Rio Grande do Sul, using the standardized rate index (SPI), degeneration anomaly index (RAI) and yield anomaly index. The results obtained demonstrate a vast difference in the spatio-temporal distribution of the rainfall and the relevance of these studies as an aid tool to plan agricultural activities such as irrigation and soil preparation to decrease the associated risks.