Study On Short-duration Rainstorm Patterns In Weihe River Basin Of Shaanxi Province

Under the dual impact of global climate change and human activities on the transformation of the underlying surface,the urban floods and flash floods caused by the frequent occurrence of heavy rainfall events in a short period of time directly affect the lives and property of the people and the safety of the ecological environment of the river basin.The rainstorm type directly affects the magnitude of the flood peak flow and the flood process.The study of the rainstorm type can provide a scientific basis for the design of the rainstorm type and the design flood,and is of great significance for flood prevention and drainage,and prevention of mountain flood disasters.Based on the self-recorded minute-by-minute rainfall data from 39 meteorological stations in the Weihe River Basin in Shaanxi Province from 1981 to 2017,the thesis selects the short-duration heavy rain and heavy rain events that meet the national standards at each station,and uses fuzzy recognition and K-means cluster analysis to analyze and study The rain-type classification and rain-type zoning of the 6-day heavy rainstorms at each meteorological station in the Weihe River Basin in Shaanxi Province at30 min,60min,90 min,120min,150 min,and 180 min were analyzed and analyzed.Rain type.The main research contents and results are as follows:(1)Single station rain pattern research.The fuzzy recognition method and K-means cluster analysis method were used to classify and summarize the storms with different durations at each station in the study area.The results show that the heavy rain type classification results of fuzzy recognition method show that most of the 39 meteorological stations have the same regularity in the realization of different durations,and the main type is the type ? with a single peak in front.K-means cluster analysis method shows that the rainstorm classification in the study area is mainly divided into five types,the type ? rainstorm is single-peak type,the rain peak is located at the front of the process,and the rainfall difference between each sub-period is not special Heavy;Type ? rainfall is concentrated in the first sub-period,with more than half of the rainfall in this period,which is quite different from other periods of rainfall;Type ? rainfall is distributed more evenly,and the rainfall in the middle of the rainfall process is slightly higher;Type ? rainfall is concentrated in In the last sub-period,more than half of the rainfall in this period is accounted for,and the rainfall in other periods is relatively small;category ? is single-peak type.The rain peak is at the back of the rainfall process,and there is no significant difference in rainfall between each sub-period.The rainstorms of most sites are mainly of type ? with a short duration.As the duration increases,the number of rainstorms of type?and?at each station in the area increases,the rainstorm process tends to be uniform,and the rain peaks move backward.(2)Research on rain type zoning.Ward cluster analysis method is used to analyze the rain classification results of each station fuzzy recognition method and K-means cluster analysis method rainstorm classification results.The results show that: when analyzing with the results of fuzzy recognition method,the types of storms and rain patterns of different durations of each station in the area are mainly type ?.When zoning,the entire study area can be regarded as the same area.The results of K-means clustering analysis were used for zoning.The zoning results of different durations were similar.The main stream of the Weihe River was used as the zoning boundary to divide the whole area into two zonings.With the increase of the duration of the rainstorm,the zoning boundary went northeast Direction of movement.After comparing and analyzing the differences between the two methods for the classification of single rainstorms and the characteristics of the rainstorm-type events at each station in space,the partition results derived from the classification results of the K-means clustering analysis method were selected.(3)Single-site generalized rain pattern research.When using the Pilgrim & Cordery method(P & C method)to calculate the generalized rain patterns of different durations at each station and found that the duration is short(30min,60min),the generalized rain patterns of the stations in the study area are mostly single-peak type.The peaks are mostly located in the second and third periods,and the rain peak position coefficients r are 0.250 and 0.208;with the increase of the duration,the number of rain peaks of the generalized rain type also increases,and there are two or more rain peaks of the generalized rain type The number of sites has also increased.(4)Zoning generalized rain type.When selecting the typical rainstorm process to calculate the generalized rain pattern of the partition,the difference of the generalized rain pattern between the different partitions is more obvious.The generalized rain patterns of the first partition and the second partition are single peak front and single peak After the type,but the difference in the different durations is small;when using the single station generalized rain type results of the P&C method to derive the regionalized generalized rain type,the generalized rain type between different partitions and the generalized rain type between different durations The difference between them is large,which can better reflect the characteristics of the generalized rain pattern between zoning and duration.Therefore,the generalized rain pattern derived from the results of the P&C method is recommended.