Temporal and Spatial Distribution Characteristics of Short-Time Heavy Rainfall in Zhejiang Province

Utilizing the hourly precipitation from reference meteorological stations and automatic meteorological stations during 2010–2019, temporal and spatial distribution characteristics of short-time heavy rainfall in Zhejiang Province were analyzed. Results show the following: 1) During 2010–2019, the cumulative frequency of short-time heavy rainfall in Zhejiang was 72601, which decayed exponentially with the increase of intensity. 2) The spatial distribution of short-time heavy rainfall is uneven. The frequency of occurrence decreased from coastal to inland, and the highest frequency occurred in the southwest of Wenzhou. As the influence system changes over time in summer, the spatial distribution of short-time heavy rainfall also changes. Short-time heavy rainfall frequently occurred in western Zhejiang from May to June, which were scattered throughout the province without obvious regional concentration characteristics in July and mainly occurred in coastal areas from August to October. 3) The diurnal variation of short-time heavy rainfall exhibited a peak of 1700 LST. The high-intensity precipitation tended to occur more in the afternoon or at dusk. In summer and autumn, short-time heavy rainfall mostly occurred in the afternoon or at dusk with a peak of 1700 LST–1800 LST. This was related to the strong subtropical high and the good heat and unstable conditions, which could easily trigger strong convective weather. In spring, except in the afternoon and at dusk, short-time heavy rainfall also frequently occurred at night and early in the morning, which may be related to the strengthening of low-level jets. The monthly variation presented a bimodal distribution, with August being the most active (26.0%) (mainly contributed to typhoon precipitation), which was followed by June and July. Moreover, there were obvious differences in the monthly variation characteristics of short-time heavy rainfall in different intensities. The interannual distribution of short-time heavy rainfall was uneven, and the interannual variability increased after 2015. The highest frequency of short-time heavy rainfall was 8728 in 2016, while the lowest frequency was only 5581 in 2017.