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- Title
Air‐Sea Interaction in the Western Tropical Pacific and its Impact on Asymmetry of the Ningaloo Niño/Niña.
- Authors
Kusunoki, Hidehiro; Kido, Shoichiro; Tozuka, Tomoki
- 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. Plain Language Summary: Ningaloo Niño is a phenomenon with anomalously warm sea surface temperature off the Western Australia coast in austral summer, while Ningaloo Niña is associated with anomalously cool sea surface temperature. These anomalous events are known to affect the marine ecosystems and Australian precipitation. It has been pointed out that the Ningaloo Niño is generally stronger than the Ningaloo Niña. A recent study showed that the oceanic teleconnection from the tropical Pacific partly contributes to this asymmetric nature. Based on numerical simulations using a simplified ocean model, it is shown that stronger easterly wind stress anomalies in the western equatorial Pacific contribute to the stronger oceanic teleconnection during the Ningaloo Niño. A heat budget analysis for the upper ocean using outputs from a more realistic regional ocean model reveals that sea surface temperature anomalies in the central‐western tropical Pacific related to this asymmetric wind stress variability are partly caused by asymmetry in oceanic vertical processes. Key Points: Ningaloo Niño/Niña show amplitude asymmetry in sea surface temperature (SST) anomalies due partly to oceanic teleconnection from the PacificStronger easterly wind anomalies in the western equatorial Pacific contribute to amplitude asymmetry in the oceanic teleconnectionThe skewed zonal wind anomalies are related to larger negative SST anomalies in the central equatorial Pacific induced by vertical processes
- Subjects
WESTERN Australia; TELECONNECTIONS (Climatology); OCEAN-atmosphere interaction; OCEAN temperature; LA Nina; ZONAL winds; MIXING height (Atmospheric chemistry)
- Publication
Geophysical Research Letters, 2021, Vol 48, Issue 13, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2021GL093370