Analysis on the characteristics of temporal and spatial distribution of hourly precipitation in Chongqing during recent 25 years

Based on the hourly precipitation data from 34 automatic stations in Chongqing from 1991 to 2015, the temporal and spatial distribution characteristics have been analyzed from the aspects of precipitation ratio, percentage of heavy precipitation, frequency of heavy precipitation, heavy precipitation event, maximum heavy precipitation and threshold of extreme heavy precipitation. The results are as follows. (1) The spatial distribution of precipitation ratio, percentage of heavy precipitation, frequency of heavy precipitation, heavy precipitation events, maximum heavy precipitation and threshold of extreme heavy precipitation are consistent with each other. The high value areas are mainly distributed in the southeast and west, while the low value areas are mainly located in the northeast and central areas. (2) The annual changes of precipitation ratio, percentage of heavy precipitation, frequency of heavy precipitation and maximum precipitation have shown fluctuations, while the change in precipitation rate is relatively small, and the latter three show the change characteristic of the same phase. On the monthly changes, the precipitation ratio is characterized by a "double peak", while the latter three are consistently characterized by a "single peak". In terms of daily changes, the high frequency of heavy precipitation mainly occurs from 03:00 BT to 05:00 BT in the morning, while the low frequency times are mainly from 13:00 BT to 15:00 BT in the afternoon. (3) In the continuity of heavy rainfall events, the duration of heavy precipitation events is consistent with the spatial distribution of the time from the beginning of precipitation to the time of the heaviest precipitation. The high value areas are mainly concentrated in the northeast and southeast, while the low value areas are mainly distributed in the central and western areas. In general, the longer the duration, the more delayed the time to produce the strongest precipitation, and the long-lasting heavy precipitation event occurred mainly at 23:00 p.m. to 04:00 a.m. in the next day. (4) The 99th, 99.5th, 99.9th percentile thresholds and 5, 10, 20, 50, and 100-year return period thresholds of the generalized extreme value (GEV) distribution functions and the maximum observed values are all consistent with heavy precipitation in spatial distribution.