Analysis on characteristics and causes of summer precipitation anomalies in Shandong in 2023

CHEN Junzhi; BO Zhongkai; XU Weiping; WANG Na

doi:10.19513/j.cnki.hyqxxb.20240725001

Abstract：In 2023,the average summer precipitation in Shandong was 414.4 mm,1.0％less than that in normal years.The precipitation processes were less,and the precipitation was mainly caused by Typhoon Doksuri.If the typhoon precipitation was removed,the summer precipitation in Shandong would be 15.9％less than that in normal years.Based on the daily precipitation observation data of 122 national meteorological stations in Shandong from 1961 to 2023 and ERA5 monthly reanalysis data,this study analyzes the characteristics of summer precipitation in Shandong in 2023 and explores the circulation patterns during the early-onset El Nino years.The results are as follows.In summer,the western section of the western Pacific subtropical high lies southward and the conditions for transfer of water vapor are poor,accompanied with positive geopotential height anomalies over Lake Baikal and weaker cold air affecting Shandong,which directly cause the less summer precipitation.The year 2023 featured an early-onset El Niño event.During such early-onset El Niño years,anomalously cold sea surface temperatures in the western Pacific trigger anomalous Walker circulation,consequently inducing a weakened and southward-displaced Hadley cell,while concurrently intensifying the Ferrel cell.Consequently,the western Pacific subtropical high shifts southward,and with subsiding airflow prevailing particularly over Shandong and insufficient moisture transport,the summer precipitation is suppressed.