2019年山东夏季降水异常特征及成因分析

Analysis on characteristics and causes of summer precipitation anomalies in Shandong in 2019

2019年夏季山东平均降水量为414.6 mm,较常年偏多3.0%。降水过程较少,时空分布不均,降水偏多主要是由台风“利奇马”影响所致,如果去除台风降水,夏季平均降水量较常年偏少41.8%。夏季西太平洋副热带高压持续偏强、偏西、偏南,配合欧亚中高纬的“两槽一脊”环流型,是去除台风影响后造成山东夏季降水明显偏少的直接原因;2018年9月至2019年6月的厄尔尼诺事件和热带印度洋海面温度的持续偏高对西太平洋副热带高压偏强、偏西、偏南起到重要作用;北大西洋海面温度三极子持续的正位相与贝加尔湖高压脊偏强有着密切联系。

In 2019,the average summer precipitation in Shandong was 414.6 mm,which is 3.0%more than that in normal years.The number of precipitation processes is less,the spatial and temporal distribution of precipitation is uneven,and the more precipitation is mainly caused by Typhoon LEKIMA.If the typhoon precipitation is removed,the summer precipitation in Shandong would be 41.8%less than that in normal years.In summer,the western Pacific subtropical high continued to be strong and lay westward and southward,accompanied with the circulation pattern of“two troughs and one ridge”in the mid-high latitude of Eurasia,which is the direct reason for the obviously less summer precipitation in Shandong as the impact of typhoon is removed.The El Nio events from September 2018 to June 2019 and the persistent high sea surface temperature in the tropical Indian Ocean play an important role for the strong,westward,and southward western Pacific subtropical high.The persistent positive phase of the North Atlantic sea surface temperature tripole is closely related to the stronger ridge over Lake Baikal.