Seasonal Dependence of the Pacific–North American Teleconnection Associated with ENSO and Its Interaction with the Annual Cycle

Abstract

The Pacific-North American (PNA) teleconnection pattern is one of the prominent atmospheric circulation modes in the extra-tropical Northern Hemisphere, and its seasonal-to-interannual predictability is suggested to originate from the El Niño–Southern Oscillation (ENSO). Intriguingly, the PNA exhibits variance at near-annual frequencies, which is related to a rapid phase reversal of the PNA during ENSO years, whereas the ENSO sea surface temperature (SST) anomalies in the tropical Pacific are evolving much slower in time. This distinct seasonal feature of the PNA can be explained by an amplitude modulation of the interannual ENSO signal by the annual cycle (i.e., the ENSO Combination Mode). The ENSO-related seasonal phase transition of the PNA is reproduced well in an atmospheric general circulation model when both the background SST annual cycle and ENSO SST anomalies are prescribed. In contrast, this characteristic seasonal evolution of the PNA is absent when the tropical Pacific background SST annual cycle is not considered in the modeling experiments. The background SST annual cycle in the tropical Pacific modulates the ENSO-associated tropical Pacific convection response, leading to a rapid enhancement of convection anomalies in winter. The enhanced convection results in a fast establishment of the large-scale PNA teleconnection during ENSO years. The dynamics of this ENSO-annual cycle interaction fills an important gap in our understanding of the seasonally modulated PNA teleconnection pattern during ENSO years.

Concurrent modes of climate variability linked to spatially compounding wind and precipitation extremes in the Northern Hemisphere

“…ENSO exhibits a strong teleconnection to the North Pacific and the PNA (Wallace and Gutzler, 1981b;Garfinkel and Hartmann, 2008;Hu et al, 2023), leading to ENSO+ and PNA+ to occur at high frequency. Such a PNA+ENSO+ combination (Figs.…”

The climate variability trio: stochastic fluctuations, El Niño, and the seasonal cycle

“…Indeed, it has been shown that the spectrum at the combination tone frequencies shows a large amplitude range when subsampling a long climate model control simulation in shorter sections (that have by chance varying ENSO variance) with a data length comparable to typical reanalysis products [see Fig. 3b Beyond this wind pattern, the Combination Mode is ubiquitous in many of ENSO's global impacts, including but not limited to extreme latitudinal swings of the South Pacific Convergence Zone (Stuecker et al 2013), extreme sea level events in the tropical Pacific (Widlansky et al 2014), the Pacific Meridional Mode (Stuecker 2018), climate impacts over East Asia (Zhang et al 2016b;Zheng et al 2020) including extreme Yangtze river flooding events (Zhang et al 2016a), precipitation in the Niño3.4 region (Fukuda et al 2021;Rodgers et al 2021), the Pacific North-American (PNA) teleconnection pattern (Hu et al 2023), and synchronized spatial shifts of the Hadley and Walker circulations (Yun et al 2021b). The ENSO Combination Mode is also detectable in eigenmodes of Indo-Pacific SSTs obtained via nonlinear Laplacian spectral analysis (Slawinska and Giannakis 2017;Giannakis and Slawinska 2018) and transfer/Koopman operator analysis (Froyland et al 2021).…”

Strengthened ENSO Amplitude Contributed to Regime Shift in the Hadley Circulation

“…However, significant interdecadal variations are reported in the relationships between the ENSO and its related climatic variabilities. For example, interdecadal shifts are observed in the associations between the ENSO and North Atlantic Oscillation (S. Hu et al., 2023; Zhang et al., 2021), precipitation over the USA (Gutzler et al., 2002; Higgins et al., 2000), sea surface temperature (SST) over the tropical Indian Ocean (Terray & Dominiak, 2005; Wang & An, 2001), and the Indian summer monsoon (Krishnamurthy & Goswami, 2000; K. K. Kumar et al., 1999). These interdecadal variations in the ENSO‐related connections are partly because the ENSO itself exhibited an interdecadal change (McPhaden et al., 2011; Zhang et al., 2019).…”