Abstract:

Based on the hourly precipitation data from 1115 automatic weather stations and and terrain height data in the central and southern regions of Hebei province from June to August of the years 2013-2020, we statistically analyzed the distribution of occurrence frequency, duration, and precipitation intensity during hourly heavy rainfall (HHR) events and rainstorm days in summer. The results show that in summer over the central and southern regions of Hebei province, the contribution rate of HHR with an occurrence frequency of 2.2 to 3.0 times per year was greater than 35%. There were six high-frequency areas for HHR, which were mainly distributed along the eastern coast of Cangzhou in a patchy pattern and in the western mountainous areas in a spot pattern. The diurnal variation in occurrence numbers of HHR less than 60 mm·h^-1 at all stations was characterized by the unimodal pattern. The occurrence numbers of HHR above 60 mm·h^-1 at all stations decreased with the increase of precipitation intensity and did not exhibit an obvious diurnal variation. In terms of precipitation properties, the convective precipitation due to cumulus was dominant at the high-HHR-frequency regions over the western mountainous areas of the central and southern Hebei province, which mostly occurred from 12:00 to 18:00. The eastern coast of Cangzhou was mostly affected by typhoons and shear lines, and HHR belonged to mixed precipitation due to stratiform clouds and cumulus clouds, usually with intense heavy precipitation.

Key words: Short-term heavy rainfall events, Precipitation contribution, Rainstorm days, Precipitation intensity