ENSO and PDO related interannual variability in the north and east‐central part of the Bolivian Altiplano in South America

Abstract

Previous studies in this region focused on interannual and interdecadal precipitation variability during Dec–Feb (summer), relating the El Niño (EN) phase to droughts. Many studies examine this variability over different parts of the Altiplano, and mountainous terrain is well‐known for producing complex climate signals as well as variability over relatively small regions. Studies that have examined climate variability over the Altiplano suggest that the El Nino Southern Oscillation (ENSO) influence is complex. The monthly precipitation, maximum and minimum temperature from 1979 to 2017 are used to examine how ENSO and PDO (Pacific decadal oscillation) influence climate conditions. Power spectra analysis determined the periodicities, and analysis of variance was applied to standardized anomalies of the three variables to evaluate PDO and ENSO as variance factors. Frequency distributions were calculated by PDO and ENSO phases, and the differences were tested using the Chi‐square test. Our results suggest a PDO and ENSO influence, displaying more dry anomalies during DJF for EN/PDO(+), in agreement with a northward position of the Bolivian high. More wet anomalies during SON (Sep–Oct–Nov) in Neutral (NEU)/PDO(+) due to an upper‐level weak westerly flow during PDO(+). For maximum temperature, a reduction in cold anomalies during EN/PDO(−) was observed along with greater warm anomalies in JJA (Jun–Jul–Aug), SON and MAM (Mar–Apr–May). Similar results were observed for NEU phase, due to a greater occurrence of high pressures centres over the region during the PDO(−). Minimum temperature results displayed more variation within stations and a less clear response to ENSO compared to PDO. The research found a clear influence of PDO in the regional climatology associated with the influence of the upper‐level jet stream using the NCEP‐NCAR composites. This provided a better understanding of these two phenomena, which would allow the production of seasonal forecasts based on ENSO and PDO using both surface and upper‐level information.

On the Impact of ENSO Cycles and Climate Change on Telescope Sites in Northern Chile

“…If anything, what is clearly visible is the variability in the maximum PWV events during the austral summers. This variability is most likely influenced by the predominant position of the Bolivian highpressure centre during summer months [32][33][34], which leads to dry anomalies during the normally wet summer for the combination of EN/PDO(+) [9]. The PWV long-term record for the Chajnantor site was analysed in [13], and no evidence of PWV trends over the 20 years of data was found, in agreement with our results for the Paranal Observatory.…”

“…Its counterpart, La Niña (LN), is marked by opposite conditions. While EN phases have been correlated with higher precipitation in the 30 • -41 • S latitudes band [8], the subtropical region, where the Atacama Desert lies, has been correlated with dryer conditions [9].…”

Precipitation over northern South America and the far‐eastern Pacific during ENSO: Phase synchronization at inter‐annual time scales

“…Do they offer new information about the climate anomalies in FEP and NSA? (Rojas-Murillo et al, 2021); (iii) Our results evidenced that over the Pacific Ocean, North Atlantic Ocean, and Southeastern Brazil, there is PS but not necessarily a change in the magnitude of the precipitation anomalies, remaining the questions: Which are the timing features or non-direct pathways through other processes of the hydroclimatic variables in this region during ENSO? ; Does desynchronization occur during ENSO transitions from Neutral to EN or Neutral to LN?…”

Exploring the causes of multicentury pluvials in the Altiplano with a climate modelling experiment

“…In addition, anomalous wet summers result from elevated moisture content in western Amazonia and/or from enhanced orographic lifting of the SALLJ (Segura et al, 2020). ENSO variability is an important driver of interannual DJF variability in the southern Altiplano, largely by modulating upper-level zonal wind anomalies (Sulca et al, 2016;Rojas-Murillo et al, 2022;Lavado-Casimiro and Espinoza, 2014;Vuille et al, 2000).…”