Several consecutive extreme cold events impacted China during the first half of winter 2020/21,breaking the low-temperature records in many cities.How to make accurate climate predictions of extreme cold events is sti...Several consecutive extreme cold events impacted China during the first half of winter 2020/21,breaking the low-temperature records in many cities.How to make accurate climate predictions of extreme cold events is still an urgent issue.The synergistic effect of the warm Arctic and cold tropical Pacific has been demonstrated to intensify the intrusions of cold air from polar regions into middle-high latitudes,further influencing the cold conditions in China.However,climate models failed to predict these two ocean environments at expected lead times.Most seasonal climate forecasts only predicted the 2020/21 La Niña after the signal had already become apparent and significantly underestimated the observed Arctic sea ice loss in autumn 2020 with a 1-2 month advancement.In this work,the corresponding physical factors that may help improve the accuracy of seasonal climate predictions are further explored.For the 2020/21 La Niña prediction,through sensitivity experiments involving different atmospheric-oceanic initial conditions,the predominant southeasterly wind anomalies over the equatorial Pacific in spring of 2020 are diagnosed to play an irreplaceable role in triggering this cold event.A reasonable inclusion of atmospheric surface winds into the initialization will help the model predict La Niña development from the early spring of 2020.For predicting the Arctic sea ice loss in autumn 2020,an anomalously cyclonic circulation from the central Arctic Ocean predicted by the model,which swept abnormally hot air over Siberia into the Arctic Ocean,is recognized as an important contributor to successfully predicting the minimum Arctic sea ice extent.展开更多
冷烧结(CSP)工艺是近年来新兴的一种高效、节能的材料方法。本工作采用CSP工艺,制备出致密度不低于97%的(1–x)BNT–x NN电介质陶瓷。研究了CSP工艺和Na Nb O_(3)含量对(1–x)BNT–x NN复相陶瓷的密度、相结构、显微形貌和介电性能的影...冷烧结(CSP)工艺是近年来新兴的一种高效、节能的材料方法。本工作采用CSP工艺,制备出致密度不低于97%的(1–x)BNT–x NN电介质陶瓷。研究了CSP工艺和Na Nb O_(3)含量对(1–x)BNT–x NN复相陶瓷的密度、相结构、显微形貌和介电性能的影响。结果表明:CSP工艺由于烧结温度低、保温时间短,可以显著降低晶粒尺寸,有效抑制Bi、Na等元素挥发,从而提高介电常数,降低介电损耗。随着Na Nb O_(3)含量的增加,(1–x)BNT–x NN复相陶瓷的剩余极化强度显著降低,并且介电常数的温度稳定性显著提升。当x=0.3时,0.7BNT–0.3NN陶瓷样品在25℃至400℃宽温范围内介电常数的变化率小于±6%,介电损耗小于5%,这表明CSP技术制备的(1–x)BNT–x NN陶瓷有望应用于温度稳定性陶瓷电容器。展开更多
基金supported by the Key Research Program of Frontier Sciences,CAS (Grant No. ZDBS-LY-DQC010)the National Natural Science Foundation of China (Grant Nos. 41876012 and 41861144015,42175045)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No.XDB42000000).
文摘Several consecutive extreme cold events impacted China during the first half of winter 2020/21,breaking the low-temperature records in many cities.How to make accurate climate predictions of extreme cold events is still an urgent issue.The synergistic effect of the warm Arctic and cold tropical Pacific has been demonstrated to intensify the intrusions of cold air from polar regions into middle-high latitudes,further influencing the cold conditions in China.However,climate models failed to predict these two ocean environments at expected lead times.Most seasonal climate forecasts only predicted the 2020/21 La Niña after the signal had already become apparent and significantly underestimated the observed Arctic sea ice loss in autumn 2020 with a 1-2 month advancement.In this work,the corresponding physical factors that may help improve the accuracy of seasonal climate predictions are further explored.For the 2020/21 La Niña prediction,through sensitivity experiments involving different atmospheric-oceanic initial conditions,the predominant southeasterly wind anomalies over the equatorial Pacific in spring of 2020 are diagnosed to play an irreplaceable role in triggering this cold event.A reasonable inclusion of atmospheric surface winds into the initialization will help the model predict La Niña development from the early spring of 2020.For predicting the Arctic sea ice loss in autumn 2020,an anomalously cyclonic circulation from the central Arctic Ocean predicted by the model,which swept abnormally hot air over Siberia into the Arctic Ocean,is recognized as an important contributor to successfully predicting the minimum Arctic sea ice extent.
文摘冷烧结(CSP)工艺是近年来新兴的一种高效、节能的材料方法。本工作采用CSP工艺,制备出致密度不低于97%的(1–x)BNT–x NN电介质陶瓷。研究了CSP工艺和Na Nb O_(3)含量对(1–x)BNT–x NN复相陶瓷的密度、相结构、显微形貌和介电性能的影响。结果表明:CSP工艺由于烧结温度低、保温时间短,可以显著降低晶粒尺寸,有效抑制Bi、Na等元素挥发,从而提高介电常数,降低介电损耗。随着Na Nb O_(3)含量的增加,(1–x)BNT–x NN复相陶瓷的剩余极化强度显著降低,并且介电常数的温度稳定性显著提升。当x=0.3时,0.7BNT–0.3NN陶瓷样品在25℃至400℃宽温范围内介电常数的变化率小于±6%,介电损耗小于5%,这表明CSP技术制备的(1–x)BNT–x NN陶瓷有望应用于温度稳定性陶瓷电容器。
