Derivation Of Rainstorm Intensity Formula And Analysis On Designing Rainstorm Rainfall Pattern In The City Of Baoji

In recent years, the rainfall characteristics are greatly changing due to global warming, the current rainstorm intensity formula of each City has a greater error with the current rainfall data. Department of Housing and the China Meteorological Administration jointly issued "on efforts to amend the rainstorm intensity formula work notice", calling on all localities to calculate new rainstorm intensity formula according to the latest rainfall data. Therefore, according to the current statement of Baoji, derivation of rainstorm intensity formula and analysis on designing rainstorm rainfall pattern have a great theoretical significance and application value.The study reviews progress and achievements on the derivating methods of rainstorm intensity formula at home and abroad, using mathematical statistics to analyze the rainfall data in 31 years(1983-2013) in Baoji Weather Stations. Using annual maximum value method and annual multi-samples method to do sampling; choosing Pearson-Ⅲ type, Gumbel and Exponential function to fit the theoretical frequency curve; based on the i-P-t table from above step, obtaining A, C, b, n values of rainstorm intensity formula with the least squares and Gauss – Newton method.Analyzing the error of each formula, the results show: Only in annual multi-samples method & exponential curve & least squares and annual maximum value method & exponential curve & least squares, the rainstorm intensity formulas meet "outdoor drainage design specifications" in 2014 edition for accuracy, and the difference between the two errors is relatively small, but the latter has much independence between years, so it is more scientific and reliable.According to Baoji rain rainstorm sample to extract parameters, counting and classifying the actual process of rainfall, establishing distribution of rainstorm pattern design of 5-minute units of time, on short duration, long duration rainstorm rainfall pattern analysis,the results show: In short duration,a single peak rainfall pattern accounts for more than 60% of the total sample, designing rainstorm rainfall pattern belongs to Chicago rain third type, which is unimodal and pre-peak; In long duration,a single peak rainfall pattern and two peaks rainfall pattern account for 71% of the total sample, designing rainstorm rainfall pattern belongs to Chicago rain third type, which is unimodal and pre-peak, and Chicago rain sixth type, which are doublet, the peak and pre-peak.