The Featuresof Summer Precipitation And The Influence Of Design Storm In Beijing Area

Based on the influence of climate warming, the original global water cycle regularity is destroyed, and the atmospheric circulation movement is changed, the frequency and intensity are increased which caused by storms, floods and other extreme weather events. Frequent rainstorm disasters made so many inconveniences for people’s production and life; also put forward severe challenges to the urban drainage planning. During the accelerating urbanization, the water logging water problem that caused by storms serious have threaten the economic development and citizen’s personal security. Design storm including analysis of rainfall in the rain, the calculation of rainfall intensity, which is the important of urban waterlogging prevention and drainage design standards. Then, it’s really practically and necessity that focus on the study at rainfall space-time change law, analysis of characteristics in the urban rain type, calculation of rainfall intensity, improve the design storm related theory.This study used 20 benchmark of Beijing weather stations rainfall data analysis and the characteristics of space-time distribution of precipitation. The result showed that:Beijing’s rainfall concentrated in six to eight months, peaked in July, rainfall accounts for 31.84% of the total rainfall; Precipitation is characterized by the daily change between 10 am and 15 for the minimum period of time, when 18 at seven in the morning for high value, accounting for 77.6% of the total precipitation, Rainfall lasted for 1 hour to 4 hours on the largest contribution to the total annual precipitation, precipitation time has the characteristic of sudden, the high rainfall intensity. The space distribution research shows that:due to the complex terrain of Beijing area, there is a big difference in different areas on the rainfall; the short duration of strong local rainfall characteristics is obvious, usually happened in central city and the northern piedmont windward.Based on the complexity of Beijing area rainfall, the urban drainage design standards need put forward higher requirements. We select the appropriate matches to using Pilgrim & Cordery method to compute the Beijing short duration design storm pattern..Results showed that the types distribution shape are consistent for schemes of 60 min and 120 min, the rain are unimodal type, the peak position, urban drainage pipeline, but on the proportional distribution of rainfall, two kinds of schemes are different. For the rainfall intensity calculation, comparing two sampling methods under the rainstorm intensity formula of accuracy, we can know that the best results calculated by the maximum sampling gumbel distribution of storm intensity formula. Combined with the actual rainfall characteristics, the intensities of rainfall between the urban station and the suburbs station, and the rainfall intensity of the single station calculation does not apply to the city throughout the whole city, so the division of rainfall in Beijing, calculated each area rainfall intensity, divide the different drainage design standards.The results of this paper can provide reliable design parameters for Beijing drainage design and provide theory support for the municipal drainage system planning.