Spatiotemporal Patterns Of ENSO-Precipitation Relationships In The Tropical Andes Of Southern Peru And Bolivia

Precipitation in the tropical Andes is highly seasonal and exhibits considerable interannual variability. The primary driver in interannual variability is the El Niño Southern Oscillation (ENSO), with most investigations reporting that the El Niño (La Niña) results in negative (positive) precipitation anomalies across the region. Recent investigations, however, have identified substantial spatiotemporal differences in ENSO-precipitation relationships. Motivated by the dissimilarity of these findings, this study examines ground-based precipitation observations (= 90% completeness from 1972-2017) from 75 high-elevation (= 2,500 m asl) meteorological stations in southern Peru and Bolivia to identify distinct groups and associated variability in precipitation characteristics (e.g., total seasonal precipitation and wet season onset). Using no spatial constraints, the K-Means algorithm optimally grouped stations into five easily identifiable groups. Groups 3, 4, and 5 farthest from the Amazon basin had significant positive (negative) precipitation anomalies (p < .05) during La Niña (El Niño), while Groups 1 and 2 closest to the Amazon had opposite relationships. Additionally, though studies have reported delays in the wet season, years characterized by El Niño had an earlier wet season onset in all five groups. These findings may improve seasonal climate prediction, water resource management, and interpretation of ice cores in the region.