中文摘要：

利用中国国家气候中心站点降水资料、NOAA全球逐日OLR资料和NCEP／NCAR再分析数据集，分析了江淮地区旱涝年及旱涝并存年夏季降水和对流的低频振荡统计特征。结果表明：江淮地区旱涝年及旱涝并存年夏季降水具有不同的振荡周期，旱年以8～16d的准双周振荡为主，涝年8-16d的准双周振荡与16-32d的周期振荡同时存在。旱涝并存年与旱涝均匀年均存在16-32d的振荡，同时还有较弱的8-16d振荡，并且旱涝并存年8-16d的振荡比旱涝均匀年更加突出，8～16d的准双周振荡可能是造成夏季降水异常的主要因子；对流的振荡周期与降水有较好的对应关系；典型旱、涝年，对流的传播特征不同，旱年准双周的低频对流以经向南传为主，涝年则主要是16～32d低频信号在纬向上的向西传播。

英文摘要：

Based on the monthly precipitation data of 160 stations and daily rainfall data of 753 stations provided by the National Climate Center of china, the daily global OLR（ outgoing long-wave radiation） data from National Oceanic and Atmospheric Administration, and the NCEP/NCAR reanalysis data, this paper studies the characteristics of low frequency oscillation of summer precipitation and convection o- ver the Yangtze-Huaihe basin during the drought/flood and drought-flood-coexistence （DFC） years. Results show that summer rainfall over the Yangtze-Huaihe basin has multi-scale periods, which are re- markably different in drought/flood and DFC years. The 8--16 d quasi-biweekly oscillation（QBWO） plays an important role in drought years,while the 16--32 d period and QBWO are found to coexist in flood years. The 16--32 d oscillation also occurs in DFC and common years, accompanied with com- paratively weak QBWO, which seems more significant in DFC. Thus, QBWO may be regarded as a vi- tal factor for summer rainfall variation. On the other hand, the oscillation period of OLR is highly corre- lated with that of summer rainfall. As regard to the propagation of low frequency convection, it is found that the 8--16 d（ 16--32 d） low frequency convection mostly propagates in the southward（westward）direction in the typical drought（flood） years.