Exploring extreme-rainfall forcings over Tucumán (Argentina) in the last 108 years and an extension to Subtropical South America

Abstract In this work the maximum daily rainfall (Rx1) is analyzed based on the longest and highest-quality daily precipitation record available in Northwestern Argentina (NWA). Rx1 is a proxy of the daily-rainfall intensity and, thus, the analysis is useful due to their relation to the flood events. The selected series has a length of 108 years and corresponds to San Miguel de Tucumán (TUC, 26.8°S, 65.2°W), a city located in Subtropical South America (SSA). The methodology proposed was detecting the period of minimum p-value (PmPV) in the linear correlation coefficients to determine closer relationships between Rx1 and large-scale climate forcings. Results show a transition from a stronger Rx1-El Niño Southern Oscillation (ENSO) association in 1945–1974 to a tighter Rx1-Southern Annular Mode (SAM) relationship in 1974–2007. The PmPV of ENSO indices aligns with the cold PDO phase, while SAM's PmPV coincides with a warm PDO phase, highlighting their significant impact on Rx1 relationships. On the other hand, using HadEX3 and ERA5 data, it was shown that the results are consistent over part of SSA respecting Rx1 and atmospheric variables behavior. Analysis reveals a shifting Rx1-ENSO relationship over NWA in contrast with the observed in eastern Argentina. Also, a positive association Rx1-SAM over NWA, western Paraguay, eastern Bolivia and central Brazil during the PDO positive phase was found. We show that changes in Rx1 arise in response to changes in ENSO and SAM teleconnections driven by PDO. Thus, this study underscores the role of global variability in driving regional extreme precipitation.