北太平洋涛动区500 hPa高度场季节变化特征及其对中国东北区降水的影响

利用国家气候中心1960~2000年500 hPa高度场10°×5°经纬度月平均资料，采用EOF、SVD方法，分析了北太平洋涛动区（25°~70°N，140°E~150°W）500 hPa高度场季节变化特征和中国东北区80个测站降水场相关。结果表明:（1）北太平洋涛动区500 hPa高度场冬季EOF第1载荷向量场呈由北向南的“-，+”波列分布，这种北南分布相反型，占总体方差贡献的40%，可以表现为北低南高，类似地面气压场涛动 (NPO) 的正位相阶段，反映了40年北太平洋中高纬度上空以东亚大槽为定常波的大气环流基本模态，亦是NPO呈正位相阶段的主要成因，反之，类似地面气压场涛动（NPO）的负位相阶段，第2载荷向量场呈整体“+”值分布，占方差贡献28%，该模态则表现为东亚大槽被长波脊替代的与气候基本模态呈相反分布的异常环流型；夏季第1载荷向量场基本模态则为全区的正值分布，占总体方差贡献的30%，第3载荷向量呈北“+”南“-”的分布，占方差贡献的13%，表明夏季500 hPa高度场NPO不是主要模态；春秋两季均呈现出较为明显的NPO模态；（2）北太平洋涛动区500 hPa高度冬季平均场与东北区夏季降水场呈由北向南的“+，-”相关波列，存在显著的相关性（α＞0.01）, 第1对SVD奇异向量占总方差贡献的49%，当NPO区前冬500 hPa高度场呈负位相阶段时，东北区夏季降水偏多，反之，东北区夏季干旱少雨，其它季节亦有类似隔季相关关系。

Seasonal Variation Features of 500 hPa Height in North Pacific Oscillation Region and Its Effect on Precipitation in Northeast China

By using of the China National Climate Center (CNCC) 500 hPa monthly mean height data (10°×5°) from 1960 to 2000 and EOF, SVD methods, the 500 hPa seasonal variation characteristics of the 500 hPa height field in the North Pacific Oscillation (NPO) region (25° to 70° N, 140° E to 150° W) region and its relation with precipitation in 80 stations over Northeast China are analyzed. The results show that: (1) In winter, the spatial structure of the first loading vector of the 500 hPa height field in NPO, similar to the positive phase of the surface pressure oscillation, is of a "﹣, +" wave distribution from north to south with the variance contribution ratio being 40%. This is a basic general circulation mode in the mid-high latitudes of North Pacific in 40 years with the East Asia Trough being a stationary wave, and it is also the main cause that NPO is mostly in positive phase. Otherwise, it is similar to the negative phase of the surface pressure oscillation. The second loading vector is of a whole "+" value distribution with the variance contribution ratio being 28%. This mode is an abnormal pattern opposite to the climatic basic mode, a long-wave ridge as a substitute for the East Asia trough. In summer, the first loading vector is of a whole "+" value distribution with the variance contribution ratio being 30%; the third is of a "+, ﹣" wave train from north to south with the variance contribution ratio being 13%. This indicates that the summer 500 hPa height NPO is not the main mode. There is a clear NPO mode in both spring and autumn. (2) There is significant correlation between the 500 hPa mean winter height field in the NPO region and summer precipitation over Northeast China (>0.01) with a "+, ﹣" wave train from north to south. The first SVD singular vector has a variance contribution ratio of 49%. The summer precipitation over Northeast is above the normal when the 500 hPa height field in the NPO region in the previous winter is in negative phase, but it is dry when the 500 hPa height is in positive phase. There is similar relationship in other seasons.