Characterization of large-scale circulation backgrounding diverse hourly heavy rainfalls in Qingdao

SUN Ying; DENG Yunchao; ZHAO Chengcheng

doi:10.13984/j.cnki.cn37-1141.2025.04.016

Abstract：In this study,we analyzed the hourly precipitation observation data collected at 7 national basic ground stations and 144 densely-distributed automatic weather stations in Qingdao region from 2006 to 2017,in combination with the NCEP/NCAR global analysis products(FNL).Our analysis fo-cused on the features of circulation backgrounding the hourly heavy rainfall events.The results showed that Qingdao experiences the hourly heavy rainfall events three times each year in average with the highest number in July and August.The spatial distribution of the hourly heavy rainfall event frequen-cy is closely related to terrain.The large value area located along the windward slope of mountain area,and the small value area located along the coast of Jiaozhou Bay.The main influencing systems on the hourly heavy rainfall events included westerly trough,cold vortex in northeastern China,low-pressure vortex or inverted trough,typhoons and their interactions with small-and medium-scale systems.The range of heavy precipitation produced by different large-scale weather systems varied significantly;local and small-scale hourly heavy rainfall events were mainly caused by the western trough and the low-pressure vortex or inverted trough while regional and large-scale ones were mainly caused by the low-pressure vortex or inverted trough.Multiple systems may interact each other,and"the north though and the south vortex"weather conditions were more likely to cause large-scale hourly heavy rainfall e-vents.Various weather systems provided different large-scale backgrounds against and effects on the hourly heavy rainfall events.The warmed low-pressure vortex or inverted trough increased the ground humidity,decreased the air pressure,and weakened the stability of atmosphere.In case of cold vortex in northeastern China,the upper-level cold air mass added the instability to atmosphere.In case of ty-phoons,there was strong vertical updrafts and convergences of airflow which resulted in significant ver-tical wind and rainfalls.