Study On The Feedbacks Relationship Between Water-energy Balance Dynamics And Underlying Surface Factors

Under the background of changing environment,the dynamic change of water-energy balance is very complex,and the feedback mechanism between the water-energy balance and underlying surface factors has not been solved.Therefore,it is important to study the dynamic change of water-energy balance and its mutual feed relationship with underlying surface factors.Based on the analysis of the spatiotemporal evolution of hydrological and meteorological elements in the Wei River Basin,this paper studied the dynamic change of water-energy balance and its driving force.The Granger causality between the parameter n and the underlying surface factors was tested.The Copula function condition probability was introduced into the study of mutual feed for the first time,and the complex mutual feed relationship between the dynamic change of water-energy balance and underlying surface factor was analyzed under the changing environment.The main research results are as follows:(1)The spatiotemporal evolution of hydrometeorological elements in Wei River Basin was revealed by the method of hydrologic statistics.The results showed that the average precipitation of Wei River Basin was not evenly distributed in space and gradually decreased from southeast to northwest.The potential evapotranspiration gradually increased from upstream to midstream to downstream.The drying index value increased from southeast to northwest,indicating that the drainage basin became drier from southeast to northwest.(2)The latest Budyko formula(Wang-Tang formula)was used,the parameter n of Budyko was fitted by the method of moving average and least square.Based on the Mann Kendall test,it was found that the Budyko parameter n in the Wei River Basin and Beiluo River Basin were not significant downward trend,while that in the Jing River Basin was significant upward trend,and the trend had the certain continuity.The results showed that the variation points of n in the Wei River Basin,Jing River Basin,and Beiluo River Basin are 1968,2003 and 1970 respectively.(3)The driving force of the dynamic change of Budyko parameter n was studied by using the cross-wavelet method.It is clarified that the influencing factors SM,NDVI,BF and EIA of the Wei River Basin had strong correlation with n.However,the relationship between the Beiluo River Basin and Jing River Basin was relatively weak.Moreover,the years with significant correlation between underlying surface factors and n were similar in the three basins,that is,the time period when underlying surface factors have significant impact on water-energy in the three basins were similar.(4)The Granger causality test was used to analyze the causality between the water-energy balance and the underlying surface factors.The results showed that in the Wei River Basin,SM and BF were one-way Granger reason of n,and the change of n to NDVI was unidirectional.In the Jing River Basin,n and NDVI were mutually fed.In the Beiluo River Basin,n and SM,n and BF all affected each other,the change of n to NDVI was unidirectional,the change of EIA to n was unidirectional(5)In view of the limitations of Granger causality test,a new mutual feed method was proposed based on the conditional probability of Copula function.The mutual feed relationship between the water-energy balance parameter n and underlying surface factor under the changing environment was revealed.The results showed that the parameters n and NDVI were mutually feed in the three basins,and the Beiluo River Basin was the strongest.And in the Beiluo River Basin and Wei River Basin,when n and NDVI took the 20th percentile,their mutual feed relationship was the strongest.The n and SM,n and BF were mutually fed in Wei River Basin and Beiluo River Basin(6)The new method based on Copula conditional probability can better describe the correlation between variables because it is coupled with the linear and non-linear characteristics between factors.It has the advantages of visualization and visualization.In addition,this method can quantitatively analyze the mutual feed relationship between parameters n and underlying surface factors under different scenarios in different basins,which provides a new way to study the mutual feed relationship of land air coupling under changing environment...