川西高原甘孜州汛期短时强降水的时空分布特征

Temporal and Spatial Distribution Characteristics of Short-Duration Heavy Rainfall in Ganzi Prefecture

利用2012—2021年4—10月甘孜州18个基准(基本)气象站和489个区域气象站逐小时降水观测资料,分析川西高原甘孜州汛期短时强降水的时空分布特征。结果表明:(1)2012—2021年甘孜州汛期短时强降水总频次为1906站次,平均每年190.6站次,且频次随量级增大呈指数衰减,15~25 mm/h短时强降水占84%以上。(2)短时强降水易发生在午后到上半夜,其日变化特征为双峰型,峰值出现在20—22时(北京时),峰值最高和次高分别为22时和20时;月变化呈单峰型,7月最多发(占30.16%),6月和8月次之;年际变化不均,2012年短时强降水发生频次最少,仅38站次,而2020年短时强降水发生频次最多,达336站次。(3)短时强降水空间分布不均,呈东多西少、南多北少的特征。发生频次最高地区位于泸定县南部,次高地区为九龙县南部。(4)受复杂地形与区域环流的共同影响,甘孜州短时强降水与海拔高度有密切关系,主要出现在1100~<3900 m海拔高度,尤其在1100~<1900 m海拔高度最易发生,其雨强最大峰值(63.3 mm/h)出现在1100~<1300 m高度范围内。

Using hourly precipitation observation data from 18 benchmark(basic)meteorological stations and 489 regional meteorological stations in Ganzi Prefecture from April to October in 2012—2021,the spatial and temporal distribution characteristics of short-term heavy precipitation in Ganzi Prefecture on the western Sichuan Plateau were statistically analyzed.The results showed that:(1)The total frequency of short-duration heavy rainfall during the flood season in Ganzi Prefecture from 2012 to 2021 was 1906 times,with an average of 190.6 times per year,and the frequency decreased exponentially with increasing magnitude,with 15~25 mm/h short-term heavy precipitation accounting for more than 84%.(2)The diurnal variation of short-duration heavy rainfall showed a bimodal pattern,with the peak occurring from 20:00 to 22:00(Beijing time),the highest and second highest peaks occurring at 22 o'clock and 20 o'clock,respectively.Short-duration heavy rainfall was more likely to occur from the afternoon to the first half of the night.The monthly variation showed a unimodal pattern,with the most occurrences in July(30.16%),followed by June and August.The interannual variation was uneven,with an average total frequency of 190 occurrences per year.The frequency of short-duration heavy rainfall in 2012 was the least,with only 38 occurrences,while in 2020,it was the highest,with 336 occurrences.(3)The frequency of short-duration heavy rainfall was higher in the southern and eastern regions than that in the northern and western regions,indicating an uneven spatial distribution.The highest frequency occurred in the southern part of Luding County,followed by the southern part of Jiulong County,which were the high-incidence areas of short-duration heavy rainfall in the entire prefecture.(4)Short-duration heavy rainfall in Ganzi Prefecture was closely related to altitude,which was the result of the interaction between complex terrain and regional circulation.Short-duration heavy rainfall mainly occurred at an altitude of 1100~3900 m,with the most occurrences at an altitude of 1100~1900 m,and the maximum peak rainfall intensity of 63.3 mm/h occurred in the altitude range of 1100~1300 m.