关键词: 自贡市, 历时, 年最大降水量, 变化特征

Abstract: Based on minutely precipitation data from 1963 to 2017 in Zigong of Sichuan Province, 12 annual maximum precipitation series with different duration from 5 min to 24 h were constructed and analyzed statistically. The results are as follows: (1) The annual maximum precipitation with different duration mainly occurred in summer (from June to August), which accounted for 88% of the total number of times. The peak time of annual maximum precipitation with different duration was mainly concentrated during nighttime (from 20:00 to next 08:00), which accounted for 74% of the total number of times, it presented obvious characteristics of night rain. (2) With the extension of precipitation duration, the standard deviation, variation coefficient, skewness coefficient, kurtosis coefficient increased, that is to say, the degree of dispersion of annual maximum precipitation gradually increased, and the slope of the “peak” became  steeper and steeper. The probability distribution of annual maximum precipitation of each duration mostly presented a positive skewness. Given the significant level of α = 0.05, the annual maximum precipitation for 10, 20, 30 min and 1 hour duration approximately presented the normal distribution. (3) The threshold value of extreme heavy rainfall of annual maximum precipitation for 1 h duration could reach 85.4 mm, which was far higher than the standard (more than 20 mm for 1 hour duration) of short-term strong precipitation set by China Meteorological Administration. Although the threshold value of weak precipitation of annual maximum precipitation with duration of 24 hours reached 70.4 mm. (4) In the past 55 years, the annual maximum precipitation with different duration had an obvious interdecadal variation characteristics. The annual maximum precipitation for 2-24 h duration  in the 1960s  and that for each duration in the 2000s were the smallest, but those for 2-24 h in the 1980s and for each duration in the 1990s were the largest. The interdecadal variations of annual maximum precipitation for 5-30 min, 1-4 hours duration in the 1990s and for 4 h in the 2000s were the most significant. (5) Since the beginning of the 2000s, the annual maximum precipitation for 1-24 hours duration  began to decrease, and it existed mutation phenomenon, but the mutation was not significant.

Key words: Zigong, duration, annual maximum precipitation, variation characteristics