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本文利用中国西北五省（区）９０个测站，１９６０～１９９０历年６～８月降水量资料，采用ＥＯＦ、ＲＥＯＦ、波谱分析及大气环流模式，对夏季降水量的空间异常特征、时间变化规律以及降水异常的主要成因进行了诊断研究和数值试验。结果表明：未旋转的前３个载荷向量场可以较好地反映西北夏季降水整体异常结构，即全区一致的多雨或少雨型；东西相反变化的东多（少）西少（多）型；南北相反变化的南多（少）北少（多）型。旋转后的前６个载荷向量可较好地代表西北夏季降水的６个主要异常敏感区：青藏高原东侧区、渭水流域区、青海高原区、北疆区、沙漠盆地区和河西走廊区。旋转主分量和代表站资料反映出近３０～６０年中，西北地区最干旱的时段在６０至７０年代。８０年代至９０年代初，除沙漠盆地外，各区程度不同地呈现出降水增加趋势。当初夏（６月）青藏高原下垫面感热异常偏强时，有利于同期西北大部地区降水偏多，而使７～８月西北西部、北部降水偏少；东部、南部降水偏多。利用ＩＡＰ２－ＬＡＧＣＭ数值试验表明，在夏季青藏高原下垫面感热大面积异常增强时，由于西太平洋副热带高压脊明显西伸，江淮处于副高西伸脊控制下，冷暖气流在长江和黄河上游交绥，有利于中国西北东南部降水偏多，多雨区?
In this paper, 90 stations in five provinces (regions) of China and precipitation data from June to August in 1960 ~ 1990 calendar year are used to analyze the characteristics of spatial anomalies and time variation of summer rainfall using EOF, REOF, spectral analysis and atmospheric circulation model And the main causes of precipitation anomalies were diagnosed and numerically tested. The results show that the unrotated first three load vector fields can well reflect the overall anomaly of summer precipitation in Northwest China, that is, the same rainy or no rainy pattern in the whole area, the eastward (less) westward (more) North and South opposite changes in the South (less) north less (more) type. The first six load vectors after rotation can well represent the six main anomalies sensitive to summer precipitation in Northwest China: the eastern side of the Qinghai-Tibet Plateau, the Weihe River Basin, the Qinghai Plateau, the Northern Territory, the Desert Basin and the Hexi Corridor. The principal component of rotation and representative station data reflect that in the last 30 to 60 years, the driest period in the northwest was between the 1960s and the 1970s. From the 1980s to the early 1990s, with the exception of the desert basin, the degree of precipitation in different districts showed a trend of increasing precipitation. At the beginning of summer (June), the sensible heat of the underlying surface of the Qinghai-Tibet Plateau is anomalously strong, which is in favor of more precipitation in most parts of Northwest China during the same period, leaving less precipitation in the western and northern parts of Northwest China from July to August; more precipitation in the eastern and southern parts. Using IAP2-LAGCM numerical experiments, it is shown that under the control of the subtropical high over the ridge, the JAC is under the control of the subtropical high west as the western Pacific subtropical ridge is obviously westward extended during summer. Sui, is conducive to more precipitation in the southeast of northwest China, rainy areas?