Rainfall variability in the region of Tangará da Serra, Mato Grosso, using the standardized precipitation index

ABSTRACT Regionally, the municipality of Tangará da Serra, Mato Grosso state, Brazil, has significant agricultural potential due to its latitudinal and orographic conditions. The variability of meteorological elements, especially rainfall, has direct impacts on the socio-environmental, economic and agricultural spheres, so assessing the intensity and trends of this variability is essential to rationalize the use of water resources, quantify impacts and for decision-making and planning to minimize possible negative impacts. In this context, the objective was to analyze the variability of precipitation and apply the Standardized Precipitation Index (SPI) to quantify drought severity. Precipitation data made available by the National Institute of Meteorology and the National Water and Sanitation Agency (ANA) between 1970 and 2023 were used. These data were analyzed for monthly and annual distribution and subjected to analysis of the probabilistic Gamma distribution model and SPI index. In general, in 47.1% of the years (25 years), the annual average precipitation was higher than the historical average (1,774.4 mm). Between 2000 and 2023, only 15% of the years exceeded the historical average precipitation. Several years with prolonged dry periods indicated by the SPI were observed in the analyzed period, with evidence of accentuation from the last 20 years; to better analyze drought events and relate their influence on agriculture, time scales of 3 and 12 months were considered.