Australia: The Land Where Time Began

A biography of the Australian continent 

Teleconnections of Austral Summer in Variability in the Indo-Pacific - Nonlinearity and Impacts on the Australian Climate

El Niņo-Southern Oscillation (ENSO) covaries with the Indian Ocean Ocean Basin Mode and the (IOBM) and the Southern Annular Mode (SAM) in the Southern Hemisphere summer. In this study the authors1 investigate how the impact on Australia of ENSO is modulated by the IOBM and the SAM. They found that the SAM has a limited modulating effect, the not modulating the teleconnection pattern of ENSO. The authors1 also found that convection anomalies induced by the ENSO were extended to the west over northern Australia and the eastern Indian Ocean by the IOBM, thereby extending the ENSO tropical teleconnection to the northwest of Australia. An equivalent-barotropic Rossby wave train is generated by the IOBM through convection anomalies over northern Australia. An anomaly centre over the Tasman Sea latitudes is shared between the wave train and the Pacific-South American Pattern (PSA), shifting the PSA anomaly centre pattern closer to Australia. The IOBM modulating effect has a strong asymmetry. The increase in rainfall during a negative phase of the IOBM, that has a tendency to coincide with La Niña events, is far greater than the rainfall reduction during a positive phase of the IOBM, which has a tendency to coincide with El Niņo events. This asymmetry of modulation is consistent with the ENSO-rainfall teleconnection  asymmetry over Australia, with the La Niña rainfall-teleconnection being stronger than the El Niņo-rainfall teleconnection. A higher coherence of convective anomalies with La Niña over northern Australia is ensured by this asymmetry of the ENSO-rainfall teleconnection or with a negative phase of the IOBM, therefore a greater modification of the PSA pattern, that underpins the asymmetric modulation role of the IOBM.

Sources & Further reading

Cai, Wenju, and Peter van Rensch. "Austral Summer Teleconnections of Indo-Pacific Variability: Their Nonlinearity and Impacts on Australian Climate." Journal of Climate (2012).

Author: M. H. Monroe
Last updated 21/10/2016
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