The Modulation of ENSO Variability in CCSM3 by Extratropical Rossby Waves
Article
Article Title | The Modulation of ENSO Variability in CCSM3 by Extratropical Rossby Waves |
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ERA Journal ID | 1978 |
Article Category | Article |
Authors | McGregor, Shayne (Author), Gupta, Alex Sen (Author), Holbrook, Neil J. (Author) and Power, Scott B. (Author) |
Journal Title | Journal of Climate |
Journal Citation | 22 (22), pp. 5839-5853 |
Number of Pages | 15 |
Year | 2009 |
Publisher | American Meteorological Society |
Place of Publication | United States |
ISSN | 0894-8755 |
1520-0442 | |
Digital Object Identifier (DOI) | https://doi.org/10.1175/2009JCLI2922.1 |
Web Address (URL) | https://journals.ametsoc.org/view/journals/clim/22/22/2009jcli2922.1.xml |
Abstract | Evidence suggests that the magnitude and frequency of the El Niño-Southern Oscillation (ENSO) changes on interdecadal time scales. This is manifest in a distinct shift in ENSO behavior during the late 1970s. This study investigates mechanisms that may force this interdecadal variability and, in particular, on modulations driven by extratropical Rossby waves. Results from oceanic shallow-water models show that the Rossby wave theory can explain small near-zonal changes in equatorial thermocline depth that can alter the amplitude of simulated ENSO events. However, questions remain over whether the same mechanism operates in more complex coupled general circulation models (CGCMs) and what the magnitude of the resulting change would be. Experiments carried out in a state-of-the-art z-coordinate primitive equation model confirm that the Rossby wave mechanism does indeed operate. The effects of these interactions are further investigated using a partial coupling (PC) technique. This allows for the isolation of the role of wind stress-forced oceanic exchanges between the extratropics and the tropics and the subsequent modulation of ENSO variability. It is found that changes in the background state of the equatorial Pacific thermocline depth, induced by a fixed offequatorial wind stress anomaly, can significantly affect the probability of ENSO events occurring. This confirms the results obtained from simpler models and further validates theories that rely on oceanic wave dynamics to generate Pacific Ocean interdecadal variability. This indicates that an improved predictive capability for seasonal-to-interannual ENSO variability could be achieved through a better understanding of extratropical-to-tropical Pacific Ocean transfers and western boundary processes. Furthermore, such an understanding would provide a physical basis to enhance multiyear probabilistic predictions of ENSO indices. © 2009 American Meteorological Society. |
Keywords | Organic Compounds; Chemical Reactions; Telephone and Other Line Communications; Electro-Optical Communication; Electronic Equipment, Radar, Radio and Television; Inorganic Compounds; Fluid Flow, General; Atmospheric Properties; Strength of Building Materials; Mechanical Properties; Waterways; Buildings and Towers; Seawater, Tides and Waves; Air-sea interaction; Air-sea interaction; MIXING AND SEPARATION; COASTAL AND OCEAN ENGINEERING; Coupled general circulation models; ENSO events; Equatorial Pacific; Extra-tropical Rossby waves; Extratropical; Extratropics; Inter-decadal variability; Interannual; Interdecadal; Oceanic waves; Pacific ocean; Predictive capabilities; Primitive equations; Probabilistic prediction; Rossby wave; Rossby wave mechanisms; Shallow-water models; Southern Oscillation; Thermocline depth; Time-scales; Tropical Pacific ocean; Western boundary; |
ANZSRC Field of Research 2020 | 370202. Climatology |
Byline Affiliations | Macquarie University |
University of New South Wales | |
University of Tasmania | |
Australian Bureau of Meteorology | |
Institution of Origin | University of Southern Queensland |
https://research.usq.edu.au/item/q66zv/the-modulation-of-enso-variability-in-ccsm3-by-extratropical-rossby-waves
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