中文摘要：

本文利用1981～2008年我国南方地区200站逐日降水量、NCEP再分析资料和NCEP气候预报系统（CFS）的模式回算数据,针对降水低频信号,分析了江淮地区夏季降水的延伸期可预报性,并选取对江淮持续性强降水有显著影响的东亚环流指数作为预报因子,以降水20～50天低频分量作为预报量,进行了针对江淮地区夏季持续性强降水过程的延伸期预报试验。结果表明,江淮地区夏季降水具有明显的20～50天周期的低频振荡特征。降水的20～50天低频振荡,尤其是峰谷值位相的变化与实际降水集中期和中断期的交替有较好的关系,研究20～50天降水低频分量的延伸预报,对于江淮地区夏季持续性强降水过程的延伸预报有一定的指示意义。本文尝试提出一种基于大气环流低频信号和数值模式预报产品的动力与统计相结合的预报方法,以期为江淮地区夏季持续性降水过程的延伸期预报提供参考。

英文摘要：

Based on the daily precipitation datasets at 200 stations in the south of China and the corresponding NCEP/NCAR daily reanalysis data from 1981 to 2008, Analysis By Synthesis （ABS） and Butterworth band-pass filter are adopted to diagnose the Low-Frequency Oscillation （LFO） characteristics of the summer rainfall over the Yangtze-Huaihe River Valley （YHRV）. And then an experiment for the Extended-Range Forecast （ERF） of persistent heavy rainfall over YHRV is made. The major conclusions are as follows： summer precipitation over YHRV has an obvious characteristic of LFO with 20-50 days period, and for climate average, the 20-50-day low-frequency components account for nearly 20%, and there are significant annual variations for the intensity of LFO signal. There is a good relationship between the 20-50-day components and actual precipitation, especially the phase changes in peak values correspond to alternation of precipitation concentrated period and break period. Therefore the 20-50-day low-frequency components of precipitation which is taken as the predictand for the ERF experiment and the persistent heavy rainfall process over YHRV are closely linked. Meanwhile based on the links between LFO of large scale circulation in East Asia and summer persistent heavy rainfall over YHRV, 10 indexes of circulation critical systems are built, which can correctly reflect the intensity and tendency of the 20-50-day low-frequency components of precipitation, and are used as predictors for the ERF experiment. Combining with the NCEP Climate Forecast System （NCEP/CFS） output the forecast model based on the LFO signal has some reference value for ERF of persistent heavy rainfall over YHRV.