Asymmetry of Indian Ocean Dipole Part I: Observational Aanalysis.

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Title:	Asymmetry of Indian Ocean Dipole Part I: Observational Aanalysis.
Authors:	洪志誠;Chi-Cherng Hong;Tim Li;LinHo;J.-S. Kug
Contributors:	地球環境暨生物資源學系(含環境教育與資源碩士班)
Keywords:	Indian Ocean;Sea surface temperature;Interannual variability;Heat budget
Date:	2008-09
Issue Date:	2014-01-17 19:30:43 (UTC+8)
Abstract:	The physical mechanism for the amplitude asymmetry of SST anomalies (SSTA) between the positive and negative phases of the Indian Ocean dipole (IOD) is investigated, using the SODA and NCAR/NCEP data. It is found that a strong negative skewness appears in the IOD east pole (IODE) in the mature phase (SON), while the skewness in the IOD west pole is insignificant. Thus, the IOD asymmetry is primarily caused by the negative skewness in IODE. A mixed layer heat budget analysis indicates that the following two air-sea feedback processes are responsible for the negative skewness. The first is attributed to the asymmetry of the wind stress-ocean advection-SST feedback. During the IOD developing stage (JJAS), the ocean linear advection tends to enhance the mixed layer temperature tendency, while nonlinear advection tends to cool the ocean in both the positive and negative events, thus contributing to the negative skewness in IODE. The second process is attributed to the asymmetry of the SST-cloud-radiation (SCR) feedback. For a positive IODE, the negative SCR feedback continues with theincrease of warm SSTA. For a negative IODE, the same negative SCR feedback works when the amplitude of SSTA is small. After reaching a critical value, the cold SSTA may completely suppress the mean convection and lead to cloud-free; a further drop of the cold SSTA does not lead to additional thermal damping so that the cold SSTA may grow faster. A wind-evaporation-SST feedback may further amplify the asymmetry induced by the aforementioned nonlinear advection and SCR feedback processes.
Relation:	Journal of Climate，Vol. 21, Issue 18，Pages 4834-4848
Appears in Collections:	[Department of Earth and Life Science] Periodical Articles

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