South American Summer Monsoon Index (SASMI)

The South American summer monsoon index (SASMI) is defined as an area-averaged seasonally (DJFM) dynamical normalized seasonality (DNS)  at 925 hPa within the South American monsoon domain (17.5°-10°S, 50°-62.5°W) (Li and Zeng, 2002, 2003, 2005). 

The South American Summer Monsoon Index (SASMI)

The normalized time series of SASMI (1948-2022).

The summer here is DJFM. The thick solid lines indicate 9-year Gaussian-type filtered values.

Correlation between precipitation and the SASMI (shading) and regression of 850-mb winds against the monsoon index (vectors) for December, January, February and March from 1979 to 2006, respectively. The shaded areas and vectors 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)