中文摘要：

用时空滤波和Morlet小波方法,分析了1958-2000年夏季东亚（20°-45°N,110°-135°E）不同纬带（由南到北分为4个区域）的降水分别与太平洋同一纬带上大气30-60 d振荡（ISO）沿纬圈传播的关系及其成因机制.发现太平洋上经向风ISO向西传播的强或弱,是东亚夏季风区降水偏多或偏少的必要条件.对逐年夏季的分析表明,无论当年东亚夏季风强与否,在所划分的几个东亚季风区所有涝的年份里,太平洋同一纬带上大气ISO向西传播都明显较强,而在这些区域绝大多数旱的年份里,相应的ISO向西传播明显较弱.进一步分析发现,经向风ISO的纬向传播对应着大气经向型环流系统的移动,向西传影响东亚夏季风区降水的ISO有来自低纬中东太平洋东风流中的低频气旋（如副热带东风带中ISO的演变）;也有来自中高纬度阿拉斯加湾及鄂霍次克海一带低频低压（如洋中槽）和高压（如阻塞高压和东北太平洋高压）的向南向西频散.因此东亚夏季旱涝不但与热带季风有关,而且与中东太平洋副热带东风系统中ISO的向西传播、中高纬度长波调整时低频扰动向西南经北太平洋副热带的传播密切相关.

英文摘要：

The relationships between the precipitation over Eastern Asia （20° - 45°N, 110° - 135°E） and the 30 - 60 day intraseasonal oscillations （ISO） over the boreal Pacific during the summer are studied. The daily wind and height fields of NCEP/NCAR reanalysis data and the 24 h precipitation data of China 687 stations during 1958 - 2000, and the pentad precipitation of CMAP/NOAA from 1979 to 2002, are all analyzed by the Space-time filter analysis. The analysis results, from every drought and flood summer for 4 different regions of East Asia respectively during 1958- 2000, showed that the precipitation amount in the East Asian summer monsoon region is well correlated to the westward propagation of 30 - 60 day ISO via the north central-eastern Pacific, and depends little on the intensity changes of the East Asian summer monsoon. And the westward ISO is usually the low-frequency low and high pressure systems from the Bay of Alaska in northeastern Pacific and the Okhotsk in the northwestern Pacific of mid-high latitudes, and the ISO evolving in subtropical easterlies. In mid-high latitude the phenomena are related to the westward propagating mid-ocean trough and block high backing off. Therefore the westward propagating ISO from the north central-eastern Pacific to East Asia is indispensable to sufficient rainfall occurring for East Asia in summer, which is resulted from long-wave adjustment process in the mid-high latitudes and ISO evolving in tropical easterlies.