An Index to Characterize the Intensity of the South China Sea Monsoon and Its Relationship with Precipitation in South China
Received:March 20, 2018  
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KeyWord:South China Sea monsoon  Precipitation in South China  Nonlinear relationship  Generalized linear models
Author NameAffiliation
ZHAO Wei Key Laboratory of Meteorological Disaster, Ministry of Education (KLME)/Joint International Research Laboratory of Climate and Environment Change (ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD), Nanjing University of Information Science and Technology, Nanjing 210044 
LU Er Key Laboratory of Meteorological Disaster, Ministry of Education (KLME)/Joint International Research Laboratory of Climate and Environment Change (ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD), Nanjing University of Information Science and Technology, Nanjing 210044 
GONG Liqing Key Laboratory of Meteorological Disaster, Ministry of Education (KLME)/Joint International Research Laboratory of Climate and Environment Change (ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD), Nanjing University of Information Science and Technology, Nanjing 210044 
WANG Huan Key Laboratory of Meteorological Disaster, Ministry of Education (KLME)/Joint International Research Laboratory of Climate and Environment Change (ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD), Nanjing University of Information Science and Technology, Nanjing 210044 
LIU Jia Meteorological Bureau of Shenzhen Municipality, Shenzhen 518040 
FANG Lujun Hangzhou Meteorology Service, Hangzhou 310051 
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Abstract:
      Seasonal change in wind strength and direction is one of the most significant characteristics of meteorological elements in the monsoon region. Lu and Chan (1999) defined an index to characterize the monsoon intensity in the South China Sea (SCS) by using the low-level wind field. For simplicity, only the meridional component was used. The study shows that the index has a good correlation with the summer rainfall in South China (SC). To modify and verify this index, by using the monthly mean NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data and the daily precipitation data of the national reference or basic synoptic stations in SC, the authors analyzed the wind projection in different directions, not the restricted southerly direction, so that the performance of the index can be improved. To quantify the relationship between the monthly mean wind projection component intensity of the SCS in different directions and the monthly precipitation in SC, the generalized linear models and two forms of the probability distribution hypothesis, namely, normal distribution, and gamma distribution, have been used. Results show that the wind projection component intensity of the SCS in the northwest (11.3°) direction has a better correlation with the summer precipitation in SC then original index. Moreover, a significant nonlinear relationship between precipitation in SC and the improved index has been observed. The generalized linear model with gamma distribution hypothesis for precipitation can obtain better realistic regression results than the generalized linear model with normal distribution hypothesis.