Features And Mechanism Of Summer Continuous Heavy Rainfall In Northern China

Use212stations data in North China, analyzed spatial and temporal characteristics of precipitation in North China, defined the summer persistent heavy rainfall events from1961to2012in North China in summer and analyzed the variations, utilization ncep reanalysis data reasearch leading cause of abnormal precipitation of the northern China summer, draw meaningful conclusions:(1) summer and July and August precipitation trends are consistent with the decrease, in June on the opposite. Northern summer and the monthly precipitation have six year returns as the same, and the summer and July and August with a period of about16years of existence on the decadal. rainfall anomaly percentage was negative distribution of north-south in1960s, eastern Hebei province, Shandong, northeast Bohai Sea region are high value center; precipitation in North China began to reduce in the1980s, precipitation anomaly percentage of Henan and Shandong province are negative. In the1990s, the rain belt position significantly southward, showing North South is negative. The overall performance of summer precipitation from west to east in North China, rainfall gradually increasing,which Less precipitation center is located in western Hebei and Shanxi and mainly rain central located in southern Henan, Shandong Peninsula, east of Beijing and Tianjin area. Rainfall center in North China are mainly located in central and southern Hebei, Beijing and Tianjin eastern regions in June. Precipitation in July increased significantly compared with June, showing an increase from west to east distribution characteristics; precipitation in August is stronger than in June, but weaker than in July, and its distribution characteristics entirely consistent with July.(2) There were287times of persistent regional heavy rainfall events in summer of north China from1961to2012, the most frequently occurring in July, followed by August, June least, there are more than60percent during a duration of4to6days. Time changes in total precipitation and the number of times of the processes, continuous precipitation process of the total days of decreasing, which lasts for days and total precipitation decreased significantly. The number of days of Persistent heavy rainfall above normal stage in the1960s and1990s.In the late1990s and in recent years, with persistent heavy rainfall days less than normal phase. Persistent heavy rainfall on summer precipitation trends in the leading role, but the region’s continued strong precipitation process on the contribution of summer precipitation interannual differences exist. Persistent heavy rainfall during the daily average number of heavy rainfall mainly concentrated in the20stations to60stations, the average annual rainfall concentrated in4～12mm, lasting longer than10days during the daily average number of stations significantly more intense precipitation, day average annual rainfall is also generally larger.(3) When the summer precipitation too much in North China, in the high latitudes there were Propagation of wave in the middle high latitudes over Eurasia, the North Atlantic and the North Pacific Ocean, respectively, the existence of the distribution characteristics of NAO and NPO, August rain is typically the East-West High-low distribution characteristics. June Rainfall in North China, the activities of Northeast Cold Vortex more significant, mainly from the low-level moisture Lake Baikal.7-8months the area east of Lake Baikal and the trough District of precipitation in North China provides cold air, moisture mainly from the Bay of Bengal. From June to August the position of the subtropical westerly jet continued north west, where rapids on the impact of precipitation in North China in June and July is most evident in the jet exit, partial years are cyclonic circulation in July cyclonic circulation strongest August weakest.