Increases in the frequency of meteorological droughts in the São Paulo state, Brazil, under climate change conditions

Climate changes are often regarded as the major factor leading to the observed increases in drought frequency and intensity worldwide. Considering the negative effects triggered by this environmental hazard, the goal of this study was to detect and quantify changes in the probability of drought events in the State of São Paulo, Brazil. The study was based on rainfall data from the NASA-POWER project, which is capable of providing meteorological series with more than 30 years of record. The drought events were quantified through the Standardized Precipitation Index (SPI), which was calculated by means of a probability-based nonstationary method designed to improve the interpretation of the index estimates under climate change conditions. The results found in this study indicated that the frequency of meteorological droughts has increased over the last years. This statement is particularly true for the months of March and April (transition periods between the regional rainy and dry seasons). Increases in drought frequency were also observed in the months of December and January (rainy season), particularly in the eastern region of the state, where the Cantareira reservoir system is situated. From the agro-environmental resource management viewpoint, we concluded that there is an increase in the risk of meteorological droughts in the State of São Paulo. From an academic viewpoint, this study provided further evidence supporting the hypothesis that climate change has increased drought frequency and intensity in several regions of the world.(author)