Abstract ID: 3.12305 | Accepted as Talk | Talk | TBA | TBA

Triple-dip La Niña was most recently observed during 2020-2023, during which a series of unusual and extreme meteorological phenomena occurred worldwide. This rare climatic phenomenon is characterized by prolonged La Niña conditions and is defined by Oceanic Niño Index (ONI) values below -0.5°C for three consecutive years. Triple-dips have only been observed four times during the period of reliable reanalysis data since 1950. The first observed triple-dip La Niña in this period occurred between 1954 and 1956 and was relatively weak, followed by the strongest episode from 1974 to 1976, and another between 1998 and 2001, apart from the recent episode Although the exact mechanisms behind these exceptional events are not fully understood, they appear to recur in every 20–25 years approximately.
As part of the Deplete and Retreat: The Future of Andean Water Towers project, this study investigates the impact of these four triple-dip La Niña episodes on temperature and precipitation dynamics across the Andes, which could directly influence the region’s water reserves. The latitudinal, topographical, and geographical diversity of the Andean mountains makes land–atmosphere interactions highly complex, which is further intensified during such extraordinary extreme climatic conditions. We use high-resolution Weather Research and Forecasting (WRF) model simulations (4 km resolution) to understand the effect of the triple-dip La Niña events on the regional Andean meteorological extremes. Here, we present the modelled results for the period of peak event intensity, identified by very high ONI value for at least three consecutive months, which also roughly overlaps with the snow accumulation season of the region. We further evaluate CMIP6 historical simulations to assess their ability to capture triple-dip La Nina episodes and investigate similar signatures in future projections to determine the potential recurrence of such episodes in the future. This study contributes to enhance our understanding of the patterns and regional climate dynamics associated with this extraordinary climate phenomenon and its implications on Andean water resources.