Changes Of Precipitation Extremes In China's Large Cities

In this study, characteristics of precipitation extremes, and their differences between the large cities with a population over one million and the other stations with a population below 500 thousand, was investigated based on 753 stations'daily precipitation data of China from 1951 to 2005. Generalized distribution method was used to calculate the extreme precipitation of the large cities. Then, the GLM method was used to analyse the relationship between total precipitation and extreme precipitation days for the large cites. Finally, the impact of ENSO on the extreme precipitation days was studied.Results revealed that the exsted methods used in extreme studies all have their advantage and disadvantage. For precipitation extremes, GEV and GPD are more suitable.Changes of precipitation extremes in large cities display a similar regional features. Moreover, the large cities also have their own characteristic of change. There were more than a half of the large cities experienced a more obvious change of the extreme precipitation than the small city stations. On the whole, if the large cities which extreme precipitation indices from 1951 to 2005 were increased, the trend of it was more obvious than the small stations around. Most of such large cities are in northern China, especially in North China. Different from the decrease trends in North China, mean extreme precipitation intensity in the larget cites in southern North China has increased obviously. The decreased trend of extreme precipitation indices are more obviously than the surrounding small cities stationsThe relation between total precipitation and extreme precipitation days for the large cites is further conducted. The relationship for the large cites is greater in northern China, especially in the western part. The relationship is less in the low reach and south of the Changjiang River.For China as a whole, ENSO plays an important part in number of extreme precipitation days in large cities. When SST of Nino3.4 is cool during summer half year (April to September), or warm in winter, extreme precipitation events are more frequency in summer half year. The impact of abnormal SST during summer half year on extreme precipitation days are more obviously than that in winter. The impact of ENSO on extreme precipitation days in Beijing is more obviously. If abnormal cold SST in winter continues in summer, there will be more extreme precipitation days in Beijing's summer time.