Meiyu In Middle And Low Reaches Of Yangtze River, Its Relationship With General Atomspheric Circulation And Forecast Experiments On Meiyu

Meiyu is analyzed in Middle and Low Reaches of Yangtze River and Anhui Province by using data of Meiyu and rainfall records from 160 stations in China and NCEP reanalysis data in recent 50 years. It is discussed that the relationship between Meiyu and atmospheric general circulation, and between Meiyu and events of El Nino. Forecast experiments on Meiyu are done. The results show that there exist great interannual variation, quasi-periodic oscillations of 3,7,14 years and the main catastrophe in 1966 by using wavelet analysis and moving t-test; 4 types (8 patterns) of main rainbands of Meiyu by using EOF Method; remarkable influences on Meiyu by subtropical high of western Pacific Ocean, especially its ridge line with correlation analysis and composite analysis. Meiyu is strong when height fields at SOOhPa present "+-+" anomalous types from low latitude to high latitude in eastern Asia. Otherwise, it is weak. Meiyu is strong when Northern Pacific Oscillation is strong and Southern Oscillation is weak. The results of prediction mark and skill mark indicate that mean generating function model (MGFM), and step-by-step regression method (SRM),or EOF analysis combined with MGFM and SRM have certain forecast ability. Meanwhile, that sea temperature, monsoon and subtropical high possess important position in forecast equation are founded.