El Niño is frequently followed by La Niña, but the opposite case rarely happens. Here we explore a mechanism for such an asymmetrical transition and its future changes. Internally, the asymmetrical response of upper ocean waves against surface wind stress anomaly exerts a primary cause of El Niño–Southern Oscillation (ENSO) transition asymmetry. Externally, the asymmetrical capacitor effects of both Indian and Atlantic Oceans play some roles in driving the ENSO transition asymmetry via the interbasin interactions. The historical runs of Coupled Model Intercomparison Project Phase 5 show that the intermodel transition asymmetry is significantly correlated with the intermodel asymmetry in ocean wave response to surface wind forcing but not with that in the interbasin interactions. In addition, the El Niño-to-La Niña transition tendency was weaker in moderate global warming scenario runs (Representative Concentration Pathway 4.5) while slightly enhanced in strong warming scenario runs (Representative Concentration Pathway 8.5). Similar changes also appeared in the asymmetrical response of ocean waves against the surface wind forcing.
Bibliographical noteFunding Information:
The authors appreciate F.-F. Jin for his helpful comments. This research was supported by Basic Science Research Program through National Research Foundation of Korea (NRF- 2017K1A3A7A03087790). The authors are grateful to all data providers. Data can be located at the following addresses: ERSSTv5 at http://www.esrl. noaa.gov/psd/data/gridded/data.noaa. ersst.v5.html, SODAv2.2.4 at http:// sodaserver.tamu.edu/assim/SODA_ 2.2.4/, and NCEP/NCAR R1 at http:// www.esrl.noaa.gov/psd/data/gridded/ data.ncep.reanalysis.html.
All Science Journal Classification (ASJC) codes
- Earth and Planetary Sciences(all)