Climate variability and anomalous atmospheric circulation during wet extreme in Curitiba - PR

Abstract

Studies show a increasing trend in wet extremes in the South Region, which stands out in the occurrence of hydrometeorological natural disasters in Brazil. Thus, this study aims to investigate the climate variability and atmospheric circulation patterns associated with wet extremes in Curitiba - PR during the summer (1980-2021), since this is the most populous municipality in the South Region. We use observed/estimated data and indices from different sources (SPEI Global Drought Monitor, ERA5, NOAA, CEDEC). Through the technique of compositions, the results show that in the wet extremes in December there is a predominance of cooling in the equatorial Pacific, favoring the positive phase of the South Atlantic Subtropical Dipole (SASDI) and negative phase of the Indian Ocean Dipole. There is also a predominance of the negative phase of the Arctic Oscillation (AO) and the North Atlantic Oscillation. In January there is a pattern of weakening of the oceanic South Atlantic Convergence Zone (SACZ), associated with the pattern of intensification of the South American low-level jet (SALLJ), and predominance of negative phase of the AO. In February, weakened SACZ predominate, associated with the pattern of intensification of the SALLJ and the southwestern branch of the South Atlantic Subtropical High, which blocks and stationary the synoptic systems on the South coast, contributing to the moisture supply. There is a predominance of Central Pacific La Niña, favoring the positive phase of the SASDI. The monitoring of climate indices and atmospheric circulation patterns can assist in predicting wet extremes in Curitiba and in preventing the impacts associated with natural hydrological disasters.