1959~2019年宣汉降水变化特征分析

选取1959~2019年宣汉气象站逐日降水数据，应用数理统计方法，分析了该地区的降水变化特征。结果表明:（1）1959年以来，宣汉年降水量呈增加趋势，气候倾向率为12.678mm/10a。（2）宣汉年均暴雨频次为4.7次/a，空间分布较为均匀，气候倾向率为0.1次/10a，集中出现在6~9月，其中7月最多，约占30%；年均大暴雨频次为0.5次/a，空间分布不均，近年频次增加，7月占比最大；伴有短时强降水的暴雨事件中，短时强降水主要出现在凌晨到上午，0~12时约占73.8%，其中又以8~10时最多。（3）宣汉年降水存在23~30a、12~20a及4~10a的周期变化特征，其中23~30a尺度代表性好，出现了3个较为完整的振荡周期。（4）宣汉暴雨频次存在25~32a、13~20a及4~10a的周期变化特征，其中13~20a尺度表现较好，出现了6.5个完整的振荡周期。 

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.