Temporal and Spatial Change Characteristics of Precipitation Concentration Degree(PCD) and Precipitation-Concentration Period(PCP) over North China in Rainy Reason

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.