Revisiting climate extremes in South America and their modulation by oceanic teleconnections

Abstract

Abstract This study characterizes spatiotemporal patterns of climate extremes in South America (SA) and assesses oceanic mode influences using daily MERGE and SAMeT data (2000–2024). Eight ETCCDI indices reveal a north–central precipitation gradient linked to the ITCZ, with dry spell maxima over central-eastern Brazil. Notable exceptions include southern Chile (orographic rainfall) and northeastern Argentina/western southern Brazil, where the SALLJ influences intense multi-day precipitation extremes. Temperature extremes show widespread warming with increasing tropical nights northward and higher frost frequency southward. Observed changes during 2000–2024 suggest drying tendencies in central-eastern SA and wetting in the northwest, though these may reflect interdecadal variability rather than long-term trends. ENSO emerges as the dominant statistical modulator, with composites and lag-correlations revealing a robust north–south dipole with regionally asymmetric signals: La Niña produces stronger drying over southeastern SA than El Niño produces wetting, consistent with Rossby wave propagation and SALLJ-related modulation, as documented in previous studies. Tropical Atlantic Variability (TAV) exerts its most robust influence over eastern Amazonia via ITCZ displacement, with weak signals elsewhere. The Combined Index produces weaker signals than ENSO alone, consistent with ENSO as the clearly dominant statistical driver of variability. These results underscore the need for mode-aware, region-specific climate services across SA.