Abstract:

This study analyzes the spatiotemporal changes in four durations of heavy precipitation (1 h, 3 h, 6 h, 12 h) for warm season (May-September) in Shaanxi Province, China during 1981—2020 based on 95 national meteorological observation stations and different statistical methods. The results show that: (1) The short duration heavy precipitation in Shaanxi mainly occurs during July-August. The regions with high frequency of heavy precipitation in four durations are located in the Qinling-Daba Mountains of southern Shaanxi, and with low frequency of that occur in the central Guanzhong Plain and the region along the Great Wall of northern Shaanxi. (2) The spatial differences of precipitation extremes in each duration are large, and the shorter duration with the stronger local distribution of the extreme precipitation. (3) In the past 40 years, the intensity and frequency of the each duration of heavy precipitation are increasing and enchancing, especially for the 3 h duration. (4) The spatial trends in each duration of heavy precipitation is non-uniformity with increased trends along the Yellow River in northern Shaanxi and south-central Shaanxi and decreased that in the south of northern Shaanxi and the central of Guanzhong Plain, and mostly, the shorter duration, the larger extent of increased trends. (5) The diurnal variation of heavy precipitation represent geographical differences in southern and northern Shaanxi. The shorter durations often accompany more obvious diurnal variation, especially for the northern Shaanxi, and the heavy precipitation usually occurs in the evening or at night, which would cause more serious disasters.

Key words: short duration heavy rainfall, change trend, spatial and temporal distribution, Shaanxi Province