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East Asian Summer Monsoon Index (EASMI)
The East Asian summer monsoon (EASM) index is defined as an area-averaged seasonally (JJA) dynamical normalized seasonality (DNS) at 850 hPa within the East Asian monsoon domain (10°-40°N, 110°-140°E) (Li and Zeng, 2002, 2003, 2005). There is an apparent negatively correlation between the EASMI and summer (JJA) rainfall in the middle and lower reaches of the Yangtze River in China, indicating drought years over the valley are associated with the strong EASM and flood years with the weak EASM.
The East Asian Summer Monsoon Index (EASMI)
The normalized time series of EASMI for the period of 1948-2009.
The summer here is JJA. The thick solid lines indicate 9-year Gaussian-type filtered values.
Correlation maps between the EASMI and summer (JJA) rainfall over (a) China (1958-99) and (b) the East Asian (1977-97). The shaded areas indicate significant at the 95% confidence level.
Correlation between precipitation and the EASMI (shading) and regression of 850-mb winds against the monsoon index (vectors) for June, July, and August from 1979 to 2006, respectively. The shaded areas and vectors indicate significant at the 95% confidence level.
Related
References
Li, J. and Q. Zeng, 2005: A new monsoon index, its interannual variability and relation with monsoon precipitation. Climatic and Environmental Research, 10(3): 351-365. Electronic version PDF
Li, J. and Q. Zeng, 2003: A new monsoon index and the geographical distribution of the global monsoons, Adv. Atmos. Sci., 20, 299-302. Electronic version PDF
Li, J. and Q. Zeng, 2002: A unified monsoon index, Geophysical Research Letters, 29(8), 1274, doi:10.1029/2001GL013874. Electronic version PDF
Li, J., and Q. 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. Electronic version PDF
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4 kilobytes |
East Asian Summer Monsoon Index (EASMI) |
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You can download this file from here (right-click then select "Save Target As" or "Save Link As"). |
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File format |
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for year = 1948 to 2009 format (1x, i4, 8f7.3) year, Jun, Jul, Aug, and summer (JJA) raw values, Jun, Jul, Aug, and summer (JJA) normalized values |
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Note: Missing values represented by 99.99. |
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The Daily East Asian Summer Monsoon Index (EASMI) Data will soon be available |
Last updated: 2010-01-15 (Jianping Li: ljp@lasg.iap.ac.cn)