【摘要】 用全国35年以上资料的672个站,讨论了华北和西北夏季降水关系及其环流特征,结果表明:(1)华北和西北夏季降水存在跷跷板式的偶极子关系,当华北夏季降水偏多时,西北降水偏少,反之亦然。华北夏季降水指数与西北夏季降水指数之间的相关系数为-0.28,超过了0.05显著性水平检验。这两条曲线的10年滑动平均的相关系数达到-0.61;而滤去年代际振荡后,它们的相关系数为-0.23,显著性水平接近0.05。这表明华北与西北夏季降水的偶极子关系主要是由年代际振荡引起的,但年际变化也是一个不可忽略的因素。(2)环流分析表明:华北与西北地区夏季降水的偶极子关系与贝加尔湖南部地区(45°~55°N,80°~110°E之间的8个格点)和西部巴尔喀什湖地区(35°~40°N,70°~90°E之间的5个格点)500 hPa高度距平符号相反有关,由它们之差(G-D)组成的华北和西北夏季降水的偶极子关系的环流指数,能很好地解释华北和西北夏季降水的偶极子关系。更多还原

【Abstract】 Based on the precipitation data of 672 stations in excess of 35 years,the relationship between the summer precipitation over Northwest and North China and its circulation features have been analyzed and discussed.The main conclusions are as follows:(1) There is a dipole relation like a seesaw structure between the summer precipitations over Northwest and North China,that is,the more precipitation in summer over North China and the less precipitation over Northwest China and vice versa.The correlation coefficient is 0.28 between the summer precipitation indexes of North and Northwest China.It has passed the confidence level of 0.05.If the time series of the indexes are processed by means of 10-year running means,their correlation coefficient is up to 0.61.After the oscillation from decade to decade is filtered from the index series,the correlation coefficient is 0.23,having close to confidence level of 0.05.These facts indicate that the dipole relation between the summer precipitations over North and Northwest China is mainly caused by the interdecadal oscillation of climate,but then the interannual change is not also a negligible factor.(2) The results elicited from circulation analysis show that the dipole relation between the summer precipitation over North and Northwest China is related to a couple of the positive and negative anomalies at 500 hPa levels,in summer,which locates in the southern region(8 grid points between 45°~55°N and 80°~110°E) of Lake Baikal and Lake Balkhash region(5 grid points between 35°~40°N and 70°~90°E).And their difference(G-D) forms a circulation index that denotes the dipole relation between the summer precipitations over North and Northwest China. By using the circulation index,the dipole relation of precipitations occurring in summer can be rationally explained.更多还原