A new perspective on increased emergence of Central Pacific ENSO in the recent two decades

Abstract

In this study, we provide a new perspective on the recent increased emergence of the central Pacific type of El Niño and Southern Oscillation (ENSO). Our results indicate that early-spring Aleutian Low (AL) intensity has a remarkable impact on the following winter ENSO especially after the late-1990s. Decrease (increase) in the early-spring AL strength tends to induce an anomalous cyclone (anticyclone) over subtropical North Pacific via wave-mean flow interaction. The anomalous cyclone (anticyclone) leads to sea surface temperature (SST) increase (decrease) in the equatorial Pacific in the following summer via wind-evaporation-SST feedback and trade wind charging mechanism, which further contributes to succeeding central Pacific-like El Niño (La Niña). This remarkable AL’s impact on ENSO is attributable to enhancement of the background trade winds, which is related to changes of both the AMO and NPGO from positive to negative phases around the late-1990s. In contrast, global warming is suggested to have a negative effect on the recent increased connection of the early-spring AL with the following winter ENSO. The results offer the potential to advance our understanding of the factors that explain decrease of the prediction skill of ENSO since the late-1990s.

Interdecadal variations in the interannual relationship between winter tropical Pacific SST and subsequent summer Arctic sea ice in early 2000s

“…Meanwhile, we found that SST anomaly in tropical Pacific can lead to circulation anomaly in the North Pacific, similar to the previous studies that El Niño (La Niña) results in the strengthening (weakening) of the Aleutian Low (Straus & Shukla, 2000). Chen et al (2023aChen et al ( , 2023b found that the decreased (increased) Aleutian Low during spring can lead to anomalous cyclones (anticyclones) over the subtropical, influencing El Niño (La Niña) in the tropical central Pacific. As a result, it is important to find out the changes in the relationship between tropical Pacific SST and North Pacific circulation under the interdecadal variations of tropical Pacific SST.…”

“…In addition, the anomalous Rossby wave train activity originating from the tropical Pacific caused by SST anomaly alters the large-scale circulation patterns in the North Atlantic, leading to the most significant tropospheric warming over northeastern Canada and Greenland, which in turn brings anomalous changes in sea ice in the Arctic (Ding et al, 2014;Wu et al, 1997;Yeh et al, 2018). Additionally, recent studies have indicated that Arctic SIC anomalies could significantly affect tropical climate systems, such as ENSO and tropical cyclone activity (Chen et al, 2020(Chen et al, , 2023a(Chen et al, , 2023b.…”

Evolution of ENSO‐related seasonal precipitation anomalies in East Asia: A robustness revisit

“…3), the changes in the correlations with East Asian precipitation seem minor in the developing phase of ENSO (Figure 4a–c), and the correlations become more appreciable in the mature and decay phases of ENSO (Figure 4d–f). The difference may be related to the interdecadal variations of ENSO and its impacts on seasonal precipitation in East Asia in the recent two decades or so (Chen et al, 2022; Hu et al, 2020a; Wu & Mao, 2016, 2018).…”

“…Following the interdecadal shift of ENSO properties that occurred in 1976/1977, another regime shift happened in 1999/2000 that featured a decrease in the ENSO variability and an increase in the ENSO frequency (Chen et al, 2022; Hu et al, 2020a). The regime shift concurs with an enhanced zonal gradient of the mean state of SST, a westward shift in the atmosphere–ocean coupling in the tropical Pacific, and an increase in the static stability of the troposphere (Hu et al, 2020a).…”

“…Thus, it is necessary to verify the robustness and the possible interdecadal variation of the connection between ENSO and East Asian seasonal precipitation, as well as the distinct impact of EP and CP ENSO with updated longer data as well as model simulations. For ENSO itself, several studies pointed out that ENSO has shown significant interdecadal variation since the late 1990s, including a decrease in variability and an increase in ENSO frequency (Hu et al, 2020a) as well as an increased emergence of CP El Niño events in the recent two decades (Chen et al, 2022). Those changes in the ENSO characteristics may lead to interdecadal variations of the ENSO impact on East Asian precipitation (e.g., Wu & Mao, 2016, 2018; Wu & Wang, 2002).…”