Air‐Sea Interaction in the Western Tropical Pacific and its Impact on Asymmetry of the Ningaloo Niño/Niña

Abstract

Ningaloo Niño/Niña is the dominant interannual sea surface temperature (SST) variability off Western Australia with the former typically stronger than the latter. Although a recent study suggested that oceanic teleconnections from the Pacific partly contribute to the amplitude asymmetry, this seems counterintuitive as La Niña, which often induces the Ningaloo Niño, is generally weaker than El Niño. Here, mechanisms of the amplitude asymmetry in the oceanic teleconnection are investigated by analyzing reanalysis data and conducting ocean model simulations. Sensitivity experiments using a linear continuously stratified model reveal that stronger easterly wind anomalies in the western equatorial Pacific contribute to the stronger oceanic teleconnection during the Ningaloo Niño. Furthermore, a mixed layer heat budget analysis with a regional ocean model shows that negatively skewed SST anomalies in the central equatorial Pacific related to the skewed wind anomalies in the western equatorial Pacific, are mainly induced by vertical advection/diffusion and entrainment.

Asymmetric Impacts of ENSO on Boreal Winter Southern Subtropical Cell in the Indian Ocean

“…Statistics have shown that El Niño events significantly affect summer monsoon rainfall, zonal wind anomalies and the following summer SST anomaly (SSTA) over the IO, but La Niña events do not (Ihara et al, 2007;Wu et al, 2021). Kusunoki et al (2020Kusunoki et al ( , 2021 reported that the impact of La Niña on Ningaloo Niño-related SSTA off western Australia is stronger than that of El Niño due to the stronger oceanic teleconnections from the Pacific. Several studies have also provided insights into the significant modulation of specific segments of the SSTC and their associated meridional heat transport by the ENSO.…”

“…Kusunoki et al. (2020, 2021) reported that the impact of La Niña on Ningaloo Niño‐related SSTA off western Australia is stronger than that of El Niño due to the stronger oceanic teleconnections from the Pacific. Several studies have also provided insights into the significant modulation of specific segments of the SSTC and their associated meridional heat transport by the ENSO.…”