中国物理B ›› 2005, Vol. 14 ›› Issue (4): 844-849.doi: 10.1088/1009-1963/14/4/037

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An improved south Asian summer monsoon index with Monte Carlo test

易燕明1, 林振敏2, 施能3, 顾骏强4   

  1. (1)Guangzhou Institute of Tropical and Oceanic Meteorology,Guangzhou,510080, China; (2)Meteorological Bureau of Guangxi Province, Nanning, 530022}, China; (3)Nanjing University of Information Science and Technology,Nanjing,210044, China;Guangzhou Institute of Tropical and Oceanic Meteorology,Guangzhou,510080, China; (4)Zhejiang Meteorological Science Research Institute,Hangzhou,310017, China
  • 收稿日期:2004-10-14 修回日期:2004-11-10 出版日期:2005-04-20 发布日期:2005-03-28
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos 40275031 and 40275028).

An improved south Asian summer monsoon index with Monte Carlo test

Shi Neng (施能)ab, Gu Jun-Qiang (顾骏强)c, Yi Yan-Ming (易燕明)b, Lin Zhen-Min (林振敏)d   

  1. a Nanjing University of Information Science and Technology, Nanjing 210044, China; b Guangzhou Institute of Tropical and Oceanic Meteorology, Guangzhou 510080, China; Zhejiang Meteorological Science Research Institute, Hangzhou 310017, China; d Meteorological Bureau of Guangxi Province, Nanning 530022, China
  • Received:2004-10-14 Revised:2004-11-10 Online:2005-04-20 Published:2005-03-28
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos 40275031 and 40275028).

摘要: The Indian monsoon intensity index suggested by Webster and Yang (WY index) is optimized and improved in this paper. At first, the area (40$^{\circ}$E--110$^{\circ}$E, 0$^{\circ}$--20$^{\circ}$N) for calculating the zonal wind-shear between 850hPa and 200hPa in the WY index is optimized and adjusted according to the significance test of differences of wind fields. Then the regionally averaged zonal wind is computed over the optimized area. Finally, the optimal linear combination of the zonal winds at the two levels is performed using the regression method, thus defining a new broad-scale circulation index for the interannual variability of the south Asian summer monsoon, i.e. the improved south Asian summer monsoon index. Results indicate that the improved south Asian summer monsoon index has two advantages: its correlation with the All Indian Summer Monsoon Rainfall index is higher than that of WY index, and its computational domain of circulation is also larger than that of WY index. The computational results based on the 1948--98 NCAR/NCEP wind data indicate that the correlation of the improved SASM index with the All Indian Summer Monsoon Rainfall index is higher than that of WY index by 0.27.

关键词: Indian summer monsoon, zonal wind-shear between 850hPa and 200hPa, south Asian summer monsoon index, Monte Carlo test

Abstract: The Indian monsoon intensity index suggested by Webster and Yang (WY index) is optimized and improved in this paper. At first, the area (40$^{\circ}$E--110$^{\circ}$E, 0$^{\circ}$--20$^{\circ}$N) for calculating the zonal wind-shear between 850hPa and 200hPa in the WY index is optimized and adjusted according to the significance test of differences of wind fields. Then the regionally averaged zonal wind is computed over the optimized area. Finally, the optimal linear combination of the zonal winds at the two levels is performed using the regression method, thus defining a new broad-scale circulation index for the interannual variability of the south Asian summer monsoon, i.e. the improved south Asian summer monsoon index. Results indicate that the improved south Asian summer monsoon index has two advantages: its correlation with the All Indian Summer Monsoon Rainfall index is higher than that of WY index, and its computational domain of circulation is also larger than that of WY index. The computational results based on the 1948--98 NCAR/NCEP wind data indicate that the correlation of the improved SASM index with the All Indian Summer Monsoon Rainfall index is higher than that of WY index by 0.27.

Key words: Indian summer monsoon, zonal wind-shear between 850hPa and 200hPa, south Asian summer monsoon inde, XMonte Carlo test

中图分类号:  (Winds and their effects)

  • 92.60.Gn
92.60.Jq (Water in the atmosphere) 92.60.Ry (Climatology, climate change and variability) 93.30.Db (Asia)