Non-stationary associations between rainfall intensity and large-scale variability in an east-Andean city over the last 108-years

Abstract

Abstract This work explores for the 1912–2019 period the interannual associations between the maximum daily rainfall (Rx1) in San Miguel de Tucumán (Argentina, 26.8°S, 65.2°W) and the large-scale variability. The flood hazard in this east-Andean city is high due to the presence of lowlands and urban stream channels with poor maintenance. We analyzed the interannual relation between Rx1 and El Niño Southern Oscillation (ENSO) and the Southern Annular mode (SAM), and the non-stationarity of these associations as a response to Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO). We compute the moving correlation for all possible window lengths between Rx1-ENSO and Rx1-SAM. As a new approach we based our analysis on the periods with most significant correlations (i.e., with minimum p-value). The aim was to obtain a period when there exists an association with maximum statistical confidence. Results suggest that Rx1 variability shows the highest statistical significance in its association with ENSO for the 1945–1974 period and with SAM for the 1974–2007 period. The overall non-stationary nature in the relations can be attributed to the phase shifts of PDO. Negative PDO and positive ENSO phases favor higher Rx1 values, while this also occurs with both positive PDO and SAM. Inverse phases favor lower Rx1 values. On the other hand, AMO phases do not influence relationships. Results highlight that processes involved in the variability of rainfall intensity are partly related to global variability modes, opening opportunities to enhance predictions in relation to the flood hazard.