Spatio-temporal Analysis Of Precipitation Simulation And Study On Precipitation Change Trend In Shiyang River Basin Based On Weather Generator

Based on the WGEN weather generator principle,this paper selects the Shiyang River Basin and its surrounding areas,including Minqin,Yongchang,Wuwei,Menyuan,Wushaoling,Jingtai,Jingyuan and Xining stations.And the spatio-temporal analysis of the precipitation simulation and the precipitation changes of the basin were completed by using the eight sites' daily precipitation data of the rainy season from 1968 to 2017.In terms of spatio-temporal analysis of precipitation simulation,The weather generator model in this article is implemented by Python programming.Based on the daily precipitation data of the rainy season of each site from 1968 to 1997,an algorithm designed in the case of improving the American empirical formula to meet the precipitation characteristics of the Shiyang River Basin was used to calculate the transition probabilities P(W|D)and P(W|W)basing on the daily precipitation data of the rainy season of each site from 1968 to 1997.And the maximum likelihood method was used to estimate the precipitation simulation parameters alpha and beta of each site for each month in each rainy season.The regional suitability test of the model was then carried out by Kolmogorov-Smirnov test(KS test)and Q-Q diagram.The results show that in addition to the extreme precipitation value,the two-parameter GAMMA distribution can better simulate the daily precipitation of the Shiyang River Basin.Finally,under the conditions of designated dry and wet days,the four statistics of monthly average precipitation days,daily average precipitation,average precipitation of rainy days and monthly maximum precipitation are used as the elements of the evaluation simulation results.The root mean square error(RMSE),mean absolute percentage error(MAPE)and mean absolute error(MAE)of the four evaluation factors about the simulated value and the actual observed value were calculated respectively in terms of time to verify the simulation effect and analyze the precipitation situation in the basin.In addition,through the spline function and natural neighborhood interpolation methods,the spatial visualization target of monthly average precipitation in each month of the rainy season is realized.At the same time,it is found that the actual precipitation in the basin and the simulated precipitation show a decreasing trend from southwest to northeast.In the analysis of the basin's precipitation change,the change was weakened by calculating the average precipitation and precipitation day of the rainy season,the average transition probability P(W|D)and P(W|W),the precipitation simulation shape parameter alpha,and the ten-year sliding average of the scale parameter beta.Then using Python to draw the anomaly map of the research elements of each site and analyze its phase change.Finally,through the climate tendency rate and Mann-Kendal non-parametric test,the overall trend analysis of each research element in each site of Shiyang River Basin was carried out.