Owing to the complexity of droughts,detailed assessments of drought events have become a key issue in water resource management and planning.In this study,three-dimensional copula models at Standard Precipitation Evap...Owing to the complexity of droughts,detailed assessments of drought events have become a key issue in water resource management and planning.In this study,three-dimensional copula models at Standard Precipitation Evapotranspiration Index(SPEI)-1,SPEI-3,SPEI-6,and SPEI-12 were used to assess drought risks in the Haihe River Basin(HRB)of China from 1961–2020.Drought duration,severity,and peak,as indicated by SPEI,were extracted based on run theory and fitted with suitable marginal distributions.The difference between the joint return period(Tor)and the co-occurrence return period(Tand)could explain the intrinsic correlation between drought characteristics.The smaller the difference,the stronger the correlation.The results showed that droughts in the north-western region of the HRB were characterized by high peak,intense severity,and long duration.In contrast,the eastern region exhibited a higher frequency of drought occurrence.Furthermore,the decreasing trend in precipitation dominated droughts,and topography of the northwest region creates the features of low annual precipitation with more days of precipitation.The drought events in the HRB were influenced by the phase shift between El Niño and La Niña.There was a strong negative phase coupling between SPEI-12 and Niño3.4(R^(2)≥0.77).The transition from La Niña to El Niño was responsible for severe droughts in the HRB.The El Niño-Southern Oscillation could predict droughts with lag times of 0.15–4.35 mon in mountainous areas.展开更多
A three-dimensional （3D） predictor-corrector finite difference method for standing wave is developed. It is applied to solve the 3D nonlinear potential flow equa- tions with a free surface. The 3D irregular tank is ...A three-dimensional （3D） predictor-corrector finite difference method for standing wave is developed. It is applied to solve the 3D nonlinear potential flow equa- tions with a free surface. The 3D irregular tank is mapped onto a fixed cubic tank through the proper coordinate transform schemes. The cubic tank is distributed by the staggered meshgrid, and the staggered meshgrid is used to denote the variables of the flow field. The predictor-corrector finite difference method is given to develop the difference equa- tions of the dynamic boundary equation and kinematic boundary equation. Experimental results show that, using the finite difference method of the predictor-corrector scheme, the numerical solutions agree well with the published results. The wave profiles of the standing wave with different amplitudes and wave lengths are studied. The numerical solutions are also analyzed and presented graphically.展开更多
基金Under the auspices of the Shandong Provincial Natural Science Foundation(No.ZR2024ME171,ZR2024QD207)the National Natural Science Foundation of China(No.41471160,42377077)。
文摘Owing to the complexity of droughts,detailed assessments of drought events have become a key issue in water resource management and planning.In this study,three-dimensional copula models at Standard Precipitation Evapotranspiration Index(SPEI)-1,SPEI-3,SPEI-6,and SPEI-12 were used to assess drought risks in the Haihe River Basin(HRB)of China from 1961–2020.Drought duration,severity,and peak,as indicated by SPEI,were extracted based on run theory and fitted with suitable marginal distributions.The difference between the joint return period(Tor)and the co-occurrence return period(Tand)could explain the intrinsic correlation between drought characteristics.The smaller the difference,the stronger the correlation.The results showed that droughts in the north-western region of the HRB were characterized by high peak,intense severity,and long duration.In contrast,the eastern region exhibited a higher frequency of drought occurrence.Furthermore,the decreasing trend in precipitation dominated droughts,and topography of the northwest region creates the features of low annual precipitation with more days of precipitation.The drought events in the HRB were influenced by the phase shift between El Niño and La Niña.There was a strong negative phase coupling between SPEI-12 and Niño3.4(R^(2)≥0.77).The transition from La Niña to El Niño was responsible for severe droughts in the HRB.The El Niño-Southern Oscillation could predict droughts with lag times of 0.15–4.35 mon in mountainous areas.
基金supported by the Yunnan Provincial Applied Basic Research Program of China(No. KKSY201207019)
文摘A three-dimensional （3D） predictor-corrector finite difference method for standing wave is developed. It is applied to solve the 3D nonlinear potential flow equa- tions with a free surface. The 3D irregular tank is mapped onto a fixed cubic tank through the proper coordinate transform schemes. The cubic tank is distributed by the staggered meshgrid, and the staggered meshgrid is used to denote the variables of the flow field. The predictor-corrector finite difference method is given to develop the difference equa- tions of the dynamic boundary equation and kinematic boundary equation. Experimental results show that, using the finite difference method of the predictor-corrector scheme, the numerical solutions agree well with the published results. The wave profiles of the standing wave with different amplitudes and wave lengths are studied. The numerical solutions are also analyzed and presented graphically.
