华北地区夏季降水变化特征和极端降水多、少年环流异常特征分析

根据1961—2004年6—8月的逐日降水资料,用Morlet小波分析和滑动平均等方法,分析了近44 a来华北地区夏季降水的年际和年代际变化特征,不同量级降水事件的发生频率和强度,极端降水时间多年和少年的大气环流差异.结果表明,华北夏季降水量总体呈下降趋势,但极端降水天气发生的次数并没有减少,强度也呈增加趋势.华北地区夏季极端降水多年,印度季风强度较强且能够伸展到我国东北地区,副热带高压强度也较强且位置偏北,在我国内蒙古北部和贝加尔湖南部有气旋性环流存在,造成极端降水量偏多;极端降水少年,印度季风强度较弱,水汽仅输送到较低纬度,从而导致北纬30°以北地区水汽大量减少,副热带高压强度较极端降水多年弱且位置偏南,造成极端降水量偏少.

Characteristics of Summer Rainfall variety in North China and signature analysis on circulation anomaly in years of extreme precipitation

Using the daily precipitation data in June-August of 1961-2004, and some methods such as Morlet wavelet analysis and moving average method, it is analyzed that the summer rainfall＇s characteristics of interannual and interdecadal variations for nearly 44 years in North China, as well as the frequency and intensity of extreme precipitation events, and the differences of the atmospheric circulation in years of extreme precipitation in North China. The results show that summer precipitation is downtrend in North of China, but the frequency of the extreme weather is not reducing, and the intensity is increasing. Extreme rainfall exists for years, the intensity of Indian monsoon is strong to extend to northeast of China, the subtropical high is strong and it＇s location is northerly, and there is a cyclonic circulation between Inner Mongolia of northern China to southern of Baikal, so it is rich of extreme precipitation; in years of poor precipitation, the strength of Indian monsoon wind is infirm, water vapor can only be transported to the lower latitude, so water vapor is much less in north of 30 °N region, the subtropical high intensity is weak and it＇s location is more southern, so it is poor of extreme precipitation.