运用新定义的降水集中度和集中期,讨论了我国华北地区雨季降水在时间上和空间上的分布特征和变化规律。结果表明,华北东部地区的降水较西部更为集中;集中期较晚,华北地区雨季降水集中期空间分布有较好的整体一致性;从长期趋势上看,集中度、集中期和雨季降水量都呈显著的下降趋势,但三者在空间上则表现出较大的区域差异,发生突变的时间都集中在20世纪70年代末至80年代初。集中度和集中期周期振荡不一致,但二者和雨季降水量在一定时间内存在相同周期;华北地区的降水量与集中度和集中期存在一致的正相关性,采用合成分析方法,华北地区多水年和少水年降水集中度的空间分布有明显的不同。青藏高原北部到蒙古高原的低压可能是影响华北降水集中度的最重要因子。华北地区雨季集中期和雨季降水量与东亚夏季风具有较好的正相关关系,华北北部地区为集中期与东亚夏季风的显著相关区。

Based on the precipitation-concentration degree(PCD) and precipitation-concentration period(PCP),the characteristics of spatial and temporal distributions and variations of precipitation over North China in the rainy season are analyzed.The result shows that the precipitation over eastern region of North China is more concentrative than western;PCP is later and spatial distribution of PCP exhibits the common features.From the long-term change,PCD,PCP and precipitation display obvious decreasing trend,but they have obvious regional difference in spatial distribution.The time of sudden change of them focus on the end of 1970's or the beginning of 1980's.The period oscillations of PCD and PCP are not consistent,but they all have the same period with precipitation in certain time.There is a positive relationship between the PCD,the PCP and precipitation over North China.Using the synthetic analysis method,it is found that the spatial distribution of PCD in the year with more precipitation is obvious different from the less one.Low pressure from north of Qinghai-Tibet Plateau to Mongolian Plateau plays an important role in PCD.There is a good positive relationship between the PCP and East-Asian summer monsoon,and the northern region of North China is more obvious region.