Australia: The Land Where Time Began

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Austral Summer Teleconnections of Indo-Pacific Variability - Nonlinearity and Impacts of the Climate of Australia

According to the authors1 during the austral summer ENSO covaries with the Indian Ocean Basin Mode (IOBM) and the Southern Annular Mode (SAM). In this article the authors1 studied the modulation of the impact of ENSO on Australia of IOBM and SAM, showing that the modulation effect of SAM is limited, particularly in that the ENSO teleconnection pattern is not modified by the SAM. ENSO-induced convection anomalies are extended westwards over northern Australia and over the eastern Indian Ocean by the IOBM, therefore 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 by the wave train and the Pacific South American pattern, which shifts the PSA pattern anomaly centre to within a closer proximity to Australia. The IOBM modulating effect has a strong asymmetry. During the negative phase of the IOBM, that usually coincides with La Niņa events, the increase in rainfall is much greater than the reduction of rainfall during a positive phase of the IOBM, which tends to coincide with El Niņo events. An asymmetry in the ENSO-rainfall teleconnection over Australia, when the La Niņa-rainfall teleconnection is stronger than the El Niņo-rainfall teleconnection, is consistent with this modulation asymmetry. A higher coherence of northern Australia convective anomalies with La Niņa or with a negative IOBM phase is ensured by this asymmetric ENSO-rainfall teleconnection, with the result that there is a greater modification of the PSA pattern, which underpins that modulation role of the IOBM.


Sources & Further reading

  1. 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: 02/04/2013
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