Two ensemble experiments were conducted using a general atmospheric circulation model. These experiments were used to investigate the impacts of initial snow anomalies over the Tibetan Plateau(TP) on China precipitati...Two ensemble experiments were conducted using a general atmospheric circulation model. These experiments were used to investigate the impacts of initial snow anomalies over the Tibetan Plateau(TP) on China precipitation prediction. In one of the experiments, the initial snow conditions over the TP were climatological values; while in the other experiment, the initial snow anomalies were snow depth estimates derived from the passive microwave remote-sensing data. In the current study, the difference between these two experiments was assessed to evaluate the impact of initial snow anomalies over the TP on simulated precipitation. The results indicated that the model simulation for precipitation over eastern China had certain improvements while applying a more realistic initial snow anomaly, especially for spring precipitation over Northeast China and North China and for summer precipitation over North China and Southeast China. The results suggest that seasonal prediction could be enhanced by using more realistic initial snow conditions over TP, and microwave remote-sensing snow data could be used to initialize climate models and improve the simulation of eastern China precipitation during spring and summer. Further analyses showed that higher snow anomalies over TP cooled the surface, resulting in lower near- surface air temperature over the TP in spring and summer. The surface cooling over TP weakened the Asian summer monsoon and brought more precipitation in South China in spring and more precipitation to Southeast China during summer.展开更多
Stability tests of three plate girders laterally unbraced on both ends, which were scale models of real plate girders in heavy plants for tower-type boilers, are presented and investigated. The applicability of code p...Stability tests of three plate girders laterally unbraced on both ends, which were scale models of real plate girders in heavy plants for tower-type boilers, are presented and investigated. The applicability of code provisions in ANSI/AISC 360-10 about such members is discussed. A nonlinear finite element analysis was carried out, considering the combined effects of plasticity, residual stress and geometrical imperfections, to simulate the stability behavior of the specimens. The reliability of the numerical model was validated by comparisons with experimental results. The results show that stability behavior of plate girders with laterally unbraced ends is widely different from that of typical simply supported thin-walled beams. The structural response is also sensitive to initial geometrical imperfections of this objects. The model is used to improve the mechanical design of transverse stiffeners over the supports. The positive effect and offsetting influence of imperfections of thicker and additional transverse stiffeners on overall stability behavior are highlighted. A few suggestions for design process are also given.展开更多
基金supported by the National Basic Research Program of China (Grant No. 2009CB421407)the Special Fund for Public Welfare (Meteorology) (Grant No. GYHY200906018)+1 种基金"Strategic Priority Research Program-Climate Change: Carbon Budget and Related Issues" of the Chinese Academy of Sciences (Grant No. XDA05110201)the National Key Technologies R&D Program of China (Grant No. 2007BAC29B03)
文摘Two ensemble experiments were conducted using a general atmospheric circulation model. These experiments were used to investigate the impacts of initial snow anomalies over the Tibetan Plateau(TP) on China precipitation prediction. In one of the experiments, the initial snow conditions over the TP were climatological values; while in the other experiment, the initial snow anomalies were snow depth estimates derived from the passive microwave remote-sensing data. In the current study, the difference between these two experiments was assessed to evaluate the impact of initial snow anomalies over the TP on simulated precipitation. The results indicated that the model simulation for precipitation over eastern China had certain improvements while applying a more realistic initial snow anomaly, especially for spring precipitation over Northeast China and North China and for summer precipitation over North China and Southeast China. The results suggest that seasonal prediction could be enhanced by using more realistic initial snow conditions over TP, and microwave remote-sensing snow data could be used to initialize climate models and improve the simulation of eastern China precipitation during spring and summer. Further analyses showed that higher snow anomalies over TP cooled the surface, resulting in lower near- surface air temperature over the TP in spring and summer. The surface cooling over TP weakened the Asian summer monsoon and brought more precipitation in South China in spring and more precipitation to Southeast China during summer.
基金The authors gratefully acknowledge sponsors of this research： National Science Foundation of China （No. 51278296）.
文摘Stability tests of three plate girders laterally unbraced on both ends, which were scale models of real plate girders in heavy plants for tower-type boilers, are presented and investigated. The applicability of code provisions in ANSI/AISC 360-10 about such members is discussed. A nonlinear finite element analysis was carried out, considering the combined effects of plasticity, residual stress and geometrical imperfections, to simulate the stability behavior of the specimens. The reliability of the numerical model was validated by comparisons with experimental results. The results show that stability behavior of plate girders with laterally unbraced ends is widely different from that of typical simply supported thin-walled beams. The structural response is also sensitive to initial geometrical imperfections of this objects. The model is used to improve the mechanical design of transverse stiffeners over the supports. The positive effect and offsetting influence of imperfections of thicker and additional transverse stiffeners on overall stability behavior are highlighted. A few suggestions for design process are also given.
