关键词: 小时强降水阈值, 时空变化, 中小尺度天气系统

Abstract: Based on the hourly precipitation data collected at 117 meteorological observation stations from May to September during 1991-2013 in Inner Mongolia, characteristics of spatial-temporal variations of hourly strong precipitation were studied with threshold values of hourly strong precipitation for each station and by Empirical Orthogonal Function (EOF) analysis method. The results showed that spatial distribution of 99% threshold value, strong precipitation frequencies and the maximum values of hourly strong precipitation occurred the same basically. There appeared increasing from the west to the east in Inner Mongolia. The high value areas were located on the windward slopes of the Yinshan Mountains and the Da Hinggan Mountains. The low value areas were located on the west of Inner Mongolia. It is founded that the frequency and intensity of hourly strong precipitation obviously increased in 21th century. Hourly strong precipitation events appeared mainly from the mid July to the early August. Furthermore, the most active period emerged from the afternoon to the evening. The strong precipitation events appeared in the midnight on the east of Inner Mongolia. The strong precipitation events sustained 1-5 hours, and the duration of 2 hours was the largest proportion.The strong precipitation events were usually caused by the mesoscale and microscale weather system and had a close relationship with the West Pacific Subtropical High.

Key words: threshold value of hourly strong precipitation, spatial-temporal variations, mesoscale and microscale weather system