The modulating influence of Indian Ocean sea surface temperatures on Australian region seasonal tropical cyclone counts

Ramsay, H; Richman, MB; Leslie, LM

The modulating influence of Indian Ocean sea surface temperatures on Australian region seasonal tropical cyclone counts

Ramsay, H Richman, MB Leslie, LM

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Publication Type:: Journal Article
Citation:: Journal of Climate, 2017, 30 (13), pp. 4843 - 4856
Issue Date:: 2017-07-01

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Field	Value	Language
dc.contributor.author	Ramsay, H	en_US
dc.contributor.author	Richman, MB	en_US
dc.contributor.author	Leslie, LM https://orcid.org/0000-0001-5616-2330	en_US
dc.date.issued	2017-07-01	en_US
dc.identifier.citation	Journal of Climate, 2017, 30 (13), pp. 4843 - 4856	en_US
dc.identifier.issn	0894-8755	en_US
dc.identifier.uri	http://hdl.handle.net/10453/125953
dc.description.abstract	© 2017 American Meteorological Society. The Australian region seasonal tropical cyclone count (TCC) maintained a robust statistical relationship with El Niño-Southern Oscillation (ENSO), with skillful forecasts of above (below) average TCC during La Niña (El Niño) years from 1969 until about 1998, weakening thereafter. The current study identifies an additional climate driver that mitigates the loss of predictive skill for Australian TCC after about 1998. It is found that the seasonal Australian TCC is strongly modulated by a southwest-to-northeast-oriented dipole in Indian Ocean sea surface temperature anomalies (SSTAs), referred to here as the transverse Indian Ocean dipole (TIOD). The TIOD emerges as the leading mode of detrended Indian Ocean SSTAs in the Southern Hemisphere during late winter and spring. Active (inactive) TC seasons are linked to positive (negative) TIOD phases, most notably during August-October immediately preceding the TC season, when SSTAs northwest of Australia, in the northeast pole of the TIOD, are positive (negative). To provide a physical interpretation of the TIOD-TCC relationship, 850-hPa zonal winds, 850-hPa relative vorticity, and 600-hPa relative humidity are composited for positive and negative TIOD phases, providing results consistent with observed TCC modulation. Correlations between ENSO and TCC weaken from 1998 onward, becoming statistically insignificant, whereas the TIOD-TCC correlation remains statistically significant until 2003. Overall, TIOD outperforms Niño-4 SSTA as a TCC predictor (46% skill increase since about 1998), when used individually or with Niño-4. The combination of TIOD and Niño 4 provide a skill increase (up to 33%) over climatology, demonstrating reliably accurate seasonal predictions of Australian region TCC.	en_US
dc.relation.ispartof	Journal of Climate	en_US
dc.relation.isbasedon	10.1175/JCLI-D-16-0631.1	en_US
dc.subject.classification	Meteorology & Atmospheric Sciences	en_US
dc.title	The modulating influence of Indian Ocean sea surface temperatures on Australian region seasonal tropical cyclone counts	en_US
dc.type	Journal Article
utslib.citation.volume	13	en_US
utslib.citation.volume	30	en_US
utslib.for	0401 Atmospheric Sciences	en_US
utslib.for	0405 Oceanography	en_US
utslib.for	0909 Geomatic Engineering	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Faculty of Science/School of Mathematical and Physical Sciences
utslib.copyright.status	open_access
pubs.issue	13	en_US
pubs.publication-status	Published	en_US
pubs.volume	30	en_US

Abstract:

© 2017 American Meteorological Society. The Australian region seasonal tropical cyclone count (TCC) maintained a robust statistical relationship with El Niño-Southern Oscillation (ENSO), with skillful forecasts of above (below) average TCC during La Niña (El Niño) years from 1969 until about 1998, weakening thereafter. The current study identifies an additional climate driver that mitigates the loss of predictive skill for Australian TCC after about 1998. It is found that the seasonal Australian TCC is strongly modulated by a southwest-to-northeast-oriented dipole in Indian Ocean sea surface temperature anomalies (SSTAs), referred to here as the transverse Indian Ocean dipole (TIOD). The TIOD emerges as the leading mode of detrended Indian Ocean SSTAs in the Southern Hemisphere during late winter and spring. Active (inactive) TC seasons are linked to positive (negative) TIOD phases, most notably during August-October immediately preceding the TC season, when SSTAs northwest of Australia, in the northeast pole of the TIOD, are positive (negative). To provide a physical interpretation of the TIOD-TCC relationship, 850-hPa zonal winds, 850-hPa relative vorticity, and 600-hPa relative humidity are composited for positive and negative TIOD phases, providing results consistent with observed TCC modulation. Correlations between ENSO and TCC weaken from 1998 onward, becoming statistically insignificant, whereas the TIOD-TCC correlation remains statistically significant until 2003. Overall, TIOD outperforms Niño-4 SSTA as a TCC predictor (46% skill increase since about 1998), when used individually or with Niño-4. The combination of TIOD and Niño 4 provide a skill increase (up to 33%) over climatology, demonstrating reliably accurate seasonal predictions of Australian region TCC.

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http://hdl.handle.net/10453/125953