The Pacific decadal oscillation modulates the relation of ENSO with the rainfall variability in coast of Ecuador

Abstract

Worldwide and likewise in Ecuador, the 1982–1983 and 1997–1998 El Niño Southern Oscillation (ENSO) events had devastating effects in the economic and human dimension. Thus, scientists and decision markers look for a deeper knowledge about ENSO and its phases El Niño (EN)/La Niña (LN). Recent research highlights the changing nature of ENSO under opposite conditions of the Pacific Decadal Oscillation (PDO), making the assessment of the ENSO–PDO relation in Ecuador urgent. This study explores the time‐frequency characteristics of rainfall in the coast of Ecuador from January to April (PC‐JA) and evaluates the influence of PDO in the relation of ENSO with PC‐JA. For this, wavelet analysis was used to asses this nonstationary problem, Five long‐term (1964–2014) ground stations were used. The main results indicate that during the warm PDO period 1980–2000, the high wavelet coherence (ca. 0.9) implies a strong coupling between ENSO and PC‐JA. For cold PDO periods, prior to 1980 and after 2005, such coupling weakens with coherence about 0.5. This might indicate that PDO influence the relation between ENSO and rainfall in the coast of Ecuador. This coupling, during warm PDO, enhances high rainfall when in phase with EN, and drought conditions in LN events. The weak coupling of ENSO‐PC‐JA during cold PDO produces high rainfall amounts in Niño Neutral conditions and droughts during Neutral and LN. To account for ENSO flavours variability, the wavelet coherence between PC‐JA and the two ENSO uncorrelated indices E and C from Takahashi et al. was studied. Interestingly, we show that PDO warm phase influences the relation of Eastern Pacific related E index with PC‐JA from 2 to 8 years periods, and that the orthogonal Central Pacific related C index is not affected. These results raise questions about the validity of ENSO indices for contrasting PDO phases.

Hydroclimate of the Andes Part II: Hydroclimate Variability and Sub-Continental Patterns

“…The AMO affects hydroclimate in this region through alterations of the SALLJ, with active SALLJ days during negative AMO phases in association with negative precipitation anomalies over the Andes-Amazon transition region and the Atlantic ITCZ (Jones and Carvalho, 2018). More recently, Campozano et al (2020) highlight that PDO modulates the ENSO influence on precipitation in the eastern Ecuadorian Andes, where the PDO warm phase enhances (reduces) precipitation when in phase with El Niño (La Niña). Furthermore, the PDO warm phase influences the connection between ENSO Canonical events and precipitation in the eastern Ecuadorian Andes while this link is not affected for the ENSO Modoki events (Campozano et al, 2020).…”

Determination of climatic conditions related to precipitation anomalies in the Tropical Andes by means of the random forest algorithm and novel climate indices

“…However, a strong influence of the oceanic indices was found (Table 5), and actually it is the highest accumulated importance of the oceanic indices among the 10 clusters. The influence that Tropical Pacific SST anomalies (mainly related to ENSO) have on precipitation in this area is well-known (Rossel and Cadier, 2009;Bendix et al, 2011;Sulca et al, 2018;Tobar and Wyseure, 2018;Zambrano Mera et al, 2018;Campozano et al, 2020) and has been confirmed by novel approaches such as the one in Landshuter et al (2020) in this region. In fact, among the oceanic indices shown in Table 4 for cluster 5, only one (TSA) is not related to ENSO.…”

“…However, one significant limitation is that these types of data are available only since 1979. These relatively short‐term measurements hinder the appropriate characterization and identification of decadal and interdecadal climatic processes (Hartigan et al ., 2020), such as the PDO and the AMO that have been found to play a role in precipitation in the region (Arias et al ., 2015b; Campozano et al ., 2020). To overcome this obstacle, alternative datasets with longer time series should be considered.…”

“…In fact, the most prominent source of temporal variability on interannual timescales is the El Niño Southern Oscillation (ENSO), that has global‐wide implications and drives widespread precipitation anomalies in South America (Aceituno, 1988; Boulanger et al ., 2005; Dijkstra, 2006; Sulca et al ., 2018). There are also other oceanic oscillations acting in decadal or longer timescales that modulate climate and precipitation in Tropical South America; the most important ones are the Pacific decadal oscillation (PDO) (Campozano et al ., 2020) and the Atlantic meridional oscillation (AMO) (Arias et al ., 2015b). Further factors that drive precipitation variability in shorter timescales in the Tropical Andes are: The Hadley Cell and the Walker Cell (Arias et al ., 2015a; Andreoli et al ., 2017), the Madden–Julian oscillation (Carvalho et al ., 2004), the low‐level jets (LLJ) (Poveda et al ., 2014), the South American Monsoon System (Liebmann and Mechoso, 2011), among others.…”

Fires in Amazonian Blackwater Floodplain Forests: Causes, Human Dimension, and Implications for Conservation

“…The PDO covers the Northern and Equatorial Pacific, while the IPO has a tripole pattern also covering the Southern Pacific, however, both oscillations are directly correlated (Henley, 2017). Several studies indicate that teleconnections between El Niño and precipitation in South America are strengthened during the warm phase of the IPO (PDO) (Andreoli and Kayano, 2005;Wang and Liu, 2016;Campozano et al, 2020;Nguyen et al, 2021).…”