Application of the vector autoregressive model and the association between ocean indicators and rainfall anomalies in eastern Paraná State, Brazil

This research aims to evaluate the impact and repercussions of sea surface temperature anomalies (SSTA) on the spatiotemporal variability of precipitation in the Upper Iguaçu (UIW), Upper Ribeira (URW), and Coastal (CW) watersheds, located in the eastern region of the state of Paraná and the southern region of Brazil. Methodological procedures used in this research include clustering analysis ( K -means) to obtain homogeneous pluviometric groups in each watershed and a vector autoregressive model (VAR) to analyze the correlation between pluviometric anomalies and maritime indicators such as the El Niño-Southern oscillation (ENSO) indicators Southern oscillation index (SOI) and Oceanic Niño index (ONI), the Pacific Decadal oscillation (PDO), and the Tropical Atlantic meridional gradient (TAMG), using data provided by the National Oceanic and Atmospheric Administration (NOAA). The spatial analysis revealed a rainfall structure of higher yearly amounts in the coastal watershed and leeward of the Serra do Mar, while an expressive sector of the Ribeira watershed presents a significant reduction of the yearly rainfall amounts compared to the sea coast. The VAR model has shown that the ONI climate indicator had the greatest significance and spatial breadth in determining the rainfall anomalies in the study area. Six out of the fifteen homogeneous groups identified in this study have rainfall anomalies related to one of the three maritime indicators (SOI, PDO, or ONI) with a predominance of a lag of 2 to 3 months. Graphical abstract