The characteristic analysis of the short-duration rainstorm extremes in four cities of Hebei province based on the Chicago method

Using the minute resolution rainfall data at Tangshan, Qinhuangdao, Baoding and Xingtai meteorological stations in Hebei province from 1961 to 2014, the annual maximum rainfall on 120 min duration is statistically analyzed, and the classification of rainfall pattern is performed with fuzzy identification method. The rainstorm pattern for 120 min duration of 2 years return period is determined at 4 meteorological stations by the Chicago method. The results show that (1) there is much difference of trend about annual maximum rainfall on 120 min duration. The fluctuation at Tangshan and Baoding is gentle, but at Xingtai is obviously rising with a climate tendency of 3.66 mm/10a. The number of the ten maximum precipitation extremes is more in 1981-2014 than in 1961-1980. (2) The dominant temporal patterns of 120 min duration rainfall process at 4 observatories are single peak, and type Ⅰ storm occurs most frequently, in which rainfall concentrated early in the storm, followed by type Ⅲ. Bimodal and uniform process occurred less frequently. (3) All the rainstorm pattern on 120 min in the 4 observatories as revealed by the Chicago method presents a single-peak pattern. The distribution characteristics of rainfall process present an increase early in the storm, then a decrease, and rainfall concentrates during its peak moment. Baoding's peak moment appears early, and Qinhuangdao's peak is late. The rainfall peak of rainstorm pattern by the Chicago method on 120 min is located before 1/3 over the whole rainfall period in Baoding and Tangshan, while those for Qinhuangdao and Xingtai are lagging.