关键词: 内蒙古河套地区, 极端降水特征, 极端降水事件, 极端降水过程, 环流背景场

Abstract: Based on  daily rainfall  from 34 national  meteorological observation stations in the Hetao area , Inner Mongolia during 1961-2018, extreme precipitation events and extreme precipitation processes were analyzed in the past 58 years. Atmospheric circulation features of typical extreme precipitation processes were aslo analyzed. The main results are as follows: (1) Average annual precipitation decreased from southeast to  northwest, and precipitation was rich from July to August. The precipitation decreased significantly in August and increased significantly in May, June and December. (2) The thresholds of extreme precipitation became lower from southeast to  northwest, the historical maximum extremum occurred in Wushenzhao  of Ordos,  the historical minimum extremum occurred in Hailisu of Bayannur. The frequency of extreme precipitation events was more than five times in most areas, the intensity became weaker from southeast to northwest. (3) The extreme precipitation events was most from July to August, and its intensity was strongest in August. The frequency of extreme precipitation events and the intensity increased significantly in September. (4) The annual average extreme precipitation process intensity decreased significantly, the process precipitation was concentrated in Tumote Zuo Banner, Ejin Horo Banner and the city of Huhhot. (5) The extreme precipitation processes were influenced by the southwest flow at the front of trough, and the plentiful vapor and exceptionally strong updraft flow could easily cause extreme precipitation events.

Key words: Hetao area of Inner Mongolia, characteristics of extreme precipitation, extreme precipitation events, extreme precipitation process, circulation background field