This study provides an integrated assessment of the climatology, variability, and long-term trends of precipitation and air temperature in a key agricultural region of northwestern São Paulo, Brazil, and evaluates their relationship with five large-scale climate oscillations. Using 40 years of high-resolution CHIRPS precipitation and ERA5-Land temperature data, the analysis identifies a significant long-term drying trend (–3.66 mm year⁻1) alongside a concurrent warming trend (+ 0.03 °C year⁻1). Breakpoint analysis reveals a statistically significant intensification of warming after 2000, indicating a shift in the thermal regime in recent decades. Composite analyses demonstrate that regional hydroclimatic variability reflects the combined influence of tropical and extratropical forcings, with seasonally varying influence. The El Niño–Southern Oscillation (ENSO) acts as the primary driver of spring precipitation, whereas the Antarctic Oscillation (AAO) predominantly controls autumn and winter temperatures and contributes to winter precipitation variability, with Atlantic variability acting as a secondary modulator. The Pacific Decadal Oscillation (PDO) further exhibits a seasonally contrasting thermal influence, with warming in autumn and cooling in winter. These results indicate increasing climate risk for the region and its agricultural systems, while also providing a basis for seasonal predictability and climate-informed resource management in transitional regions.
Avila et al. (Sat,) studied this question.