Monsoon-like Southwest Australian Circulation Index (SWACI)

The monsoon-like southwest Australian circulation (SWAC) index is defined as an area-averaged dynamical normalized seasonality (DNS) at 850 hPa within the southwest Austrailan circulation domain (35°-25°S, 100°-145°E) (Li and Zeng, 2002; Feng et al., 2010). There is an apparent significant correlation between the SWACI and rainfall in the southwest Western Australia (SWWA) in both early and late winter, indicating drought years over the SWWA are associated with the weak SWAC.

The Southwest Australian Circulation Index (SWACI)

The normalized time series of SWACI during the austral winter half year (May to October) for the period of 1948-2023.

Correlation maps between the SWACI and Australian rainfall during (a) early winter (May to July), (b) late winter (August to October), and (c) winter half year (May to October) during 1948-2007. The shaded areas indicate significant at the 95% confidence level.

Related References

• Li, J. P., J. Feng, and Y. Li, 2011: A possible cause of decreasing summer rainfall in northeast Australia. Int. J. Climatol., 31, doi: 10.1002/joc.2328. PDF
• Li, J. P., Z. W. Wu, Z. H. Jiang, and J. H. He, 2010: Can global warming strengthen the East Asian summer monsoon?. J. Climate, 23, 6696-6705. PDF
• Feng, J., J. P. Li, and Y. Li, 2010: A monsoon-like Southwest Australian circulation and its relation with rainfall in Southwest Western Australia. J. Climate, 23: 1334-1353. PDF
• Wang, B., Z. W. Wu, J. P. Li, J. Liu, C. P. Chang, Y. H. Ding, and G. X. Wu, 2008: How to measure the strength of the East Asian summer monsoon. J. Climate, 21, 4449-4462. PDF
• Li, J. P., and Q. C. Zeng, 2005: A new monsoon index, its interannual variability and relation with monsoon precipitation. Climatic and Environmental Research, 10(3): 351-365. PDF　
• Li, J. P., and Q. C. Zeng, 2003: A new monsoon index and the geographical distribution of the global monsoons. Adv. Atmos. Sci., 20, 299-302. PDF 　
• Li, J. P., and Q. C. Zeng, 2002: A unified monsoon index. Geophysical Research Letters, 29(8), 1274, doi:10.1029/2001GL013874. PDF 
• Zeng, Q. C., and J. P. Li, 2002: On the Interaction between Northern and Southern Hemispheric Atmospheres and the Essence of Tropical Monsoon. Chinese Journal of Atmospheric Sciences, 26, 207-226. PDF
• Li, J. P., and Q. C. Zeng, 2000: Significance of the normalized seasonality of wind field and its rationality for characterizing the monsoon. Science in China (D), 43(6): 647-653. PDF 

Subroutine for Dynamical Normalized Seasonality (DNS): seasonality(mx,my,v1,v2,v3,v4,fai0,grdy,suv)