In this paper, the possible reason of Tibetan Plateau （TP） temperature increasing was investigated. An increase in T min （minimum temperature） plays a robust role in increased TP temperature, which is strongly rel...In this paper, the possible reason of Tibetan Plateau （TP） temperature increasing was investigated. An increase in T min （minimum temperature） plays a robust role in increased TP temperature, which is strongly related to SST over the warm pool of the western Pacific Ocean, the subtropical westerly jet stream （SWJ）, and the tropical easterly upper jet stream （TEJ）, and the 200hPa zonal wind in East Asia. Composite analysis of the effects of SST, SWJ, and TEJ on pre and postabrupt changes in T a （annual temperature） and T min over the TP shows remarkable differences in SST, SWJ, and TEJ. A lag correlation between T a /T min , SST, and SWJ/TEJ shows that changes in SST occur ahead of changes in T a /T min by approximately one to three seasons. Partial correlations between T a /T min , SST, and SWJ/TEJ show that the effect of SWJ on T a /T min is more significant than the effect of SST. Furthermore, simulations with a community atmospheric model （CAM3.0） were performed, showing a remarkable increase in T a over the TP when the SST increased by 0.5 ？ C. The main increase in T a and T min in the TP can be attributed to changes in SWJ. A possible mechanism is that changes in SST force the TEJ to weaken, move south, and lead to increased SWJ and movement of SWJ northward. Finally, changes in the intensity and location of the SWJ cause an increase in T a /T min . It appears that TP warming is governed primarily by coherent TEJ and SWJ variations that act as the atmospheric bridges to remote SSTs in warmpool forcing.展开更多
By using isothermal double hit compression tests and applying the 2% offset method, a new model was developed to predict the microstructural evolution of Nb-bearing steels at temperatures above and below the start tem...By using isothermal double hit compression tests and applying the 2% offset method, a new model was developed to predict the microstructural evolution of Nb-bearing steels at temperatures above and below the start temperature of strain-induced precipitation （Tp）. The Tp was developed as a function of true strain, initial austenite grain size and the Nb content. The activation energy of static recrystallization （Qrex） was expressed as a function of the content of different alloy elements. It was found that Nb played the most important role in increasing the value of Qrex, The microstructural observations and measurements confirmed the validity of the model developed in the present investigation.展开更多
基金supported by the National Basic Research Program of China (Grant No 2007CB411506)National Natural Science Foundation of China (Grant Nos 4107108 and 40875050)
文摘In this paper, the possible reason of Tibetan Plateau （TP） temperature increasing was investigated. An increase in T min （minimum temperature） plays a robust role in increased TP temperature, which is strongly related to SST over the warm pool of the western Pacific Ocean, the subtropical westerly jet stream （SWJ）, and the tropical easterly upper jet stream （TEJ）, and the 200hPa zonal wind in East Asia. Composite analysis of the effects of SST, SWJ, and TEJ on pre and postabrupt changes in T a （annual temperature） and T min over the TP shows remarkable differences in SST, SWJ, and TEJ. A lag correlation between T a /T min , SST, and SWJ/TEJ shows that changes in SST occur ahead of changes in T a /T min by approximately one to three seasons. Partial correlations between T a /T min , SST, and SWJ/TEJ show that the effect of SWJ on T a /T min is more significant than the effect of SST. Furthermore, simulations with a community atmospheric model （CAM3.0） were performed, showing a remarkable increase in T a over the TP when the SST increased by 0.5 ？ C. The main increase in T a and T min in the TP can be attributed to changes in SWJ. A possible mechanism is that changes in SST force the TEJ to weaken, move south, and lead to increased SWJ and movement of SWJ northward. Finally, changes in the intensity and location of the SWJ cause an increase in T a /T min . It appears that TP warming is governed primarily by coherent TEJ and SWJ variations that act as the atmospheric bridges to remote SSTs in warmpool forcing.
基金This work was supported by the National Natural Science Foundation of China （No. 50474086 and No. 50334010） the Program for New Century Excellent Talents in Universities （NCET-04-0278） of the Ministry of Education of China.
文摘By using isothermal double hit compression tests and applying the 2% offset method, a new model was developed to predict the microstructural evolution of Nb-bearing steels at temperatures above and below the start temperature of strain-induced precipitation （Tp）. The Tp was developed as a function of true strain, initial austenite grain size and the Nb content. The activation energy of static recrystallization （Qrex） was expressed as a function of the content of different alloy elements. It was found that Nb played the most important role in increasing the value of Qrex, The microstructural observations and measurements confirmed the validity of the model developed in the present investigation.
