Analysis on the Characteristics of Precipitation Changes in Xuanhan from 1959 to 2019

Using the precipitation data of Xuanhan National General Meteorological Station from 1959 to 2019, the characteristics of precipitation changes in Xuanhan was analyzed with mathematical statistics. The results show that: (1) Since 1959, the annual precipitation in Xuanhan has shown an increasing trend, and the climate trend tendency rate is 12.678mm/10a. (2) The average annual frequency of heavy rains is 4.7times/a, and the distribution is relatively even. The climate tendency rate is 0.1times/10a, which is concentrated in the period from Jun to September, and the largest proportion is in July, nearly 30%. The average frequency of heavy rainstorms is 0.5times/a, and the distribution is uneven. The frequency has increased in recent years, with the largest proportion in July. Heavy rains accompanied by short-term heavy precipitation in various precipitation periods, short-term heavy precipitation mainly occurs from early morning to morning, accounting for about 73.8% from 0:00 to 12:00, among which the most occurs from 8:00 to 10:00. (3) The annual precipitation has obvious periodic changes at the three scales of 23~30a, 12~20 a, and 4~10a. Among them, the 23~30a scale is representative, and there are three relatively complete oscillation cycles. (4) The frequency of torrential rains changes significantly in the three-scale cycles of 25~32a, 13-20a, and 4~10a. Among them, the 13~20a scale performs better, with 6.5 complete shock cycles.