Climate extreme events and their changes can generally exert severe impacts on society and ecosystems and cause large economic losses each year. Robust projections of their future changes are thus urgently important f...Climate extreme events and their changes can generally exert severe impacts on society and ecosystems and cause large economic losses each year. Robust projections of their future changes are thus urgently important for policymaking to provide reliable information with respect to climate mitigation and adaptation.展开更多
By using the Betts-Miller-Janji＇c,Grell-Devenyi,and Kain-Fritsch cumulus convective parameterization schemes in the Weather Research and Forecasting（WRF） model,long time simulations from 2000 to 2009 are conducted ...By using the Betts-Miller-Janji＇c,Grell-Devenyi,and Kain-Fritsch cumulus convective parameterization schemes in the Weather Research and Forecasting（WRF） model,long time simulations from 2000 to 2009 are conducted to investigate the impacts of different cumulus convective parameterization schemes on summermonsoon precipitation simulation over China.The results show that all the schemes have the capability to reasonably reproduce the spatial and temporal distributions of summer monsoon precipitation and the corresponding background circulation.The observed north-south shift of monsoon rain belt is also well simulated by the three schemes.Detailed comparison indicates that the Grell-Devenyi scheme gives a better performance than the others.Deficiency in simulated water vapor transport is one possible reason for the precipitation simulation bias.展开更多
This study investigates the relationship between the summer North Atlantic Oscillation （SNAO） and the simultaneous Northern Hemisphere （NH） land surface air temperature （SAT） by using the Climate Research Unit ...This study investigates the relationship between the summer North Atlantic Oscillation （SNAO） and the simultaneous Northern Hemisphere （NH） land surface air temperature （SAT） by using the Climate Research Unit （CRU） data. The results show that the SNAO is related to NH land SAT, but this linkage has varied on decadal timescales over the last 52 years, with a strong connection appearing after the late 1970s, but a weak connection before. The mechanism governing the relationship between the SNAO and NH land SAT is discussed based on the NCEP/NCAR reanalysis data. The results indicate that such a variable relationship may result from changes of the SNAO mode around the late 1970s. The SNAO pattern was centered mainly over the North Atlantic before the late 1970s, and thus had a weak influence on the NH land SAT. But after the late 1970s, the SNAO pattern shifted eastward and its southern center was enhanced in magnitude and extent, which transported the SNAO signal to the North Atlantic surrounding continents and even to central East Asia via an upper level wave train along the Asian jet.展开更多
[目的]评价基于显微CT(Micro-CT)骨内微血管造影进行骨内微血管显影和三维重建在缺血性股骨头坏死(osteonecrosis of femoral head,ONFH)研究中的应用价值,实现在三维空间内同时定量评价骨显微结构及骨矿物量和骨内微血管。[方法]采用...[目的]评价基于显微CT(Micro-CT)骨内微血管造影进行骨内微血管显影和三维重建在缺血性股骨头坏死(osteonecrosis of femoral head,ONFH)研究中的应用价值,实现在三维空间内同时定量评价骨显微结构及骨矿物量和骨内微血管。[方法]采用局部液氮冷冻和射频加热交替的方法建立鸸鹋塌陷性股骨头坏死动物模型,右侧为手术侧,左侧为对照侧。术后定期进行核磁检查,证实造模成功后自鸸鹋腹主动脉注入亚纳米级硫酸钡明胶混悬液进行下肢血管造影,取下肢股骨标本进行Micro-CT扫描,通过软件进行骨内微血管的二维及三维重建,同时结合Micro-CT骨显微结构研究,并将标本常规HE染色进行组织学检查。[结果]在术后12周证实出现股骨头塌陷,至16周16只动物出现股骨头塌陷。Micro-CT图像骨小梁结构及骨内血管显示清晰,与对照侧相比鸸鹋股骨头坏死塌陷后股骨头部的骨小梁厚度、骨体积分数增加,骨矿物量及骨小梁间距减小,血管体积分数减小,且差异均具有统计学意义。[结论]以亚纳米级硫酸钡作为造影剂,Micro-CT骨内微血管造影可以在不破坏骨标本的基础下清晰的显示骨内微血管,不干扰影像及组织学检查,并实现骨内微血管与骨显微结构及矿物量同时定量评价;在股骨头坏死的研究中具有重要价值,可以用于股骨头坏死造模评估、骨坏死和修复机制及治疗评价的研究。展开更多
Elevation-dependent warming(EDW),whereby warming rates are stratified by elevation,may increase the threat to the life-supporting solid water reservoir on the Tibetan Plateau.Previous studies have debated whether EDW ...Elevation-dependent warming(EDW),whereby warming rates are stratified by elevation,may increase the threat to the life-supporting solid water reservoir on the Tibetan Plateau.Previous studies have debated whether EDW exists and how it is driven.Using temperatures at 133 weather stations on the Tibetan Plateau during 17 different periods generated using a 30-year sliding window over 1973-2018,this study finds that the existence of EDW varies as the period moves forward,and critically it has become more severe over time.During the early part of the record with weaker regional warming,there were limited changes in snow depth and no EDW,but as time advances and regional warming intensifies,snow depth declines significantly at higher elevations,causing development of EDW.We conclude that enhanced regional warming has caused decreases in snow depth,largely controlling the pattern of EDW on the Tibetan Plateau.This may explain contrasting conclusions on EDW from previous studies which have used data for different periods,and our findings support enhanced EDW and more severe depletion of the Tibetan Plateau solid water reserves in a warmer future.展开更多
基金This work was jointly supported by the National Natural Science Foundation of China(41991284 and 41922034)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA23090102)the National Key Research and Development Program of China(2016YFA0602401).
文摘Climate extreme events and their changes can generally exert severe impacts on society and ecosystems and cause large economic losses each year. Robust projections of their future changes are thus urgently important for policymaking to provide reliable information with respect to climate mitigation and adaptation.
文摘利用相关分析和经验正交分解方法对过去57aNCEP-NCAR夏季亚洲-北太平洋地区海平面气压场进行了分析,揭示了一种新的遥相关模态,即阿拉伯半岛-北太平洋型遥相关(Arabian Peninsula-North Pacific Oscillation,APNPO).研究表明,APNPO在本质上反映的是对流层低层北太平洋高压和南亚夏季风低压之间的一种共变特征,它的变化与亚洲夏季风的变化之间有着密切的联系.在年际尺度上,APNPO与东亚夏季风(East Asian summer monsoon,EASM)和南亚夏季风(South Asian summer monsoon,SASM)均存在显著的关联;在年代际尺度上,该遥相关与东亚夏季风的关系更为密切:两者均在20世纪60年代中期和70年代末发生了两次明显的年代际突变.通过分析与APNPO相关的环流场,探讨了APNPO与亚洲夏季风联系的物理过程.发现当APNPO偏强时,索马里急流、SASM气流、EASM气流以及南亚高压均得到加强,同时还通过高层的纬向波列在中国东北地区上空形成了一个异常的反气旋性环流.此外,强的APNPO还可加强对亚洲季风区的水汽输送,由此在印度半岛及中国华北地区造成强的水汽辐合.所有的这些大气环流和水汽条件的改变最终导致亚洲夏季风及印度和中国华北地区降水的异常.研究还发现APNPO的变化从春到夏具有较好的持续性,春季的APNPO与亚洲夏季风变化也存在显著的相关关系.从这个意义上讲,春季APNPO变化的超前性对于后期亚洲夏季风降水的预测具有潜在的重要参考价值.
基金Supported by the National Basic Research and Development (973) Program of China (2009CB421406)National Natural Science Foundation of China (40875048 and 40821092)China Meteorological Administration Special Public Welfare Research Fund for Meteorological Profession (GYHY200906018)
文摘By using the Betts-Miller-Janji＇c,Grell-Devenyi,and Kain-Fritsch cumulus convective parameterization schemes in the Weather Research and Forecasting（WRF） model,long time simulations from 2000 to 2009 are conducted to investigate the impacts of different cumulus convective parameterization schemes on summermonsoon precipitation simulation over China.The results show that all the schemes have the capability to reasonably reproduce the spatial and temporal distributions of summer monsoon precipitation and the corresponding background circulation.The observed north-south shift of monsoon rain belt is also well simulated by the three schemes.Detailed comparison indicates that the Grell-Devenyi scheme gives a better performance than the others.Deficiency in simulated water vapor transport is one possible reason for the precipitation simulation bias.
基金supported by Chinese Academy of Sciences(Grant Nos.KZCX2-YW-Q1-02 and KZCX2-YW-217)the National Natural Science Foundation of China(Grant Nos.40905041,40631005,and 90711004)the IAP innovation program(Grant No.IAP07412)
文摘This study investigates the relationship between the summer North Atlantic Oscillation （SNAO） and the simultaneous Northern Hemisphere （NH） land surface air temperature （SAT） by using the Climate Research Unit （CRU） data. The results show that the SNAO is related to NH land SAT, but this linkage has varied on decadal timescales over the last 52 years, with a strong connection appearing after the late 1970s, but a weak connection before. The mechanism governing the relationship between the SNAO and NH land SAT is discussed based on the NCEP/NCAR reanalysis data. The results indicate that such a variable relationship may result from changes of the SNAO mode around the late 1970s. The SNAO pattern was centered mainly over the North Atlantic before the late 1970s, and thus had a weak influence on the NH land SAT. But after the late 1970s, the SNAO pattern shifted eastward and its southern center was enhanced in magnitude and extent, which transported the SNAO signal to the North Atlantic surrounding continents and even to central East Asia via an upper level wave train along the Asian jet.
文摘[目的]评价基于显微CT(Micro-CT)骨内微血管造影进行骨内微血管显影和三维重建在缺血性股骨头坏死(osteonecrosis of femoral head,ONFH)研究中的应用价值,实现在三维空间内同时定量评价骨显微结构及骨矿物量和骨内微血管。[方法]采用局部液氮冷冻和射频加热交替的方法建立鸸鹋塌陷性股骨头坏死动物模型,右侧为手术侧,左侧为对照侧。术后定期进行核磁检查,证实造模成功后自鸸鹋腹主动脉注入亚纳米级硫酸钡明胶混悬液进行下肢血管造影,取下肢股骨标本进行Micro-CT扫描,通过软件进行骨内微血管的二维及三维重建,同时结合Micro-CT骨显微结构研究,并将标本常规HE染色进行组织学检查。[结果]在术后12周证实出现股骨头塌陷,至16周16只动物出现股骨头塌陷。Micro-CT图像骨小梁结构及骨内血管显示清晰,与对照侧相比鸸鹋股骨头坏死塌陷后股骨头部的骨小梁厚度、骨体积分数增加,骨矿物量及骨小梁间距减小,血管体积分数减小,且差异均具有统计学意义。[结论]以亚纳米级硫酸钡作为造影剂,Micro-CT骨内微血管造影可以在不破坏骨标本的基础下清晰的显示骨内微血管,不干扰影像及组织学检查,并实现骨内微血管与骨显微结构及矿物量同时定量评价;在股骨头坏死的研究中具有重要价值,可以用于股骨头坏死造模评估、骨坏死和修复机制及治疗评价的研究。
基金supported by the Second Tibetan Plateau Scientific Expedition and Research(STEP)Program(2019QZKK0102)the National Natural Science Foundation of China(41991281 and 41775076)Youth Innovation Promotion Association of Chinese Academy of Sciences(2018103)。
文摘Elevation-dependent warming(EDW),whereby warming rates are stratified by elevation,may increase the threat to the life-supporting solid water reservoir on the Tibetan Plateau.Previous studies have debated whether EDW exists and how it is driven.Using temperatures at 133 weather stations on the Tibetan Plateau during 17 different periods generated using a 30-year sliding window over 1973-2018,this study finds that the existence of EDW varies as the period moves forward,and critically it has become more severe over time.During the early part of the record with weaker regional warming,there were limited changes in snow depth and no EDW,but as time advances and regional warming intensifies,snow depth declines significantly at higher elevations,causing development of EDW.We conclude that enhanced regional warming has caused decreases in snow depth,largely controlling the pattern of EDW on the Tibetan Plateau.This may explain contrasting conclusions on EDW from previous studies which have used data for different periods,and our findings support enhanced EDW and more severe depletion of the Tibetan Plateau solid water reserves in a warmer future.
