Extreme Cold Events from East Asia to North America in Winter 2020/21: Comparisons,Causes, and Future Implications     

Xiangdong ZHANG  Yunfei FU  Zhe HAN  James E.OVERLAND  Annette RINKE  Han TANG  Timo VIHMA  Muyin WANG 《大气科学进展》2022,39(4):553-565

Three striking and impactful extreme cold weather events successively occurred across East Asia and North America during the mid-winter of 2020/21.These events open a new window to detect possible underlying physical processes.The analysis here indicates that the occurrences of the three events resulted from integrated effects of a concurrence of anomalous thermal conditions in three oceans and interactive Arctic-lower latitude atmospheric circulation processes,which were linked and influenced by one major sudden stratospheric warming(SSW).The North Atlantic warm blob initiated an increased poleward transient eddy heat flux,reducing the Barents-Kara seas sea ice over a warmed ocean and disrupting the stratospheric polar vortex(SPV)to induce the major SSW.The Rossby wave trains excited by the North Atlantic warm blob and the tropical Pacific La Nina interacted with the Arctic tropospheric circulation anomalies or the tropospheric polar vortex to provide dynamic settings,steering cold polar air outbreaks.The long memory of the retreated sea ice with the underlying warm ocean and the amplified tropospheric blocking highs from the midlatitudes to the Arctic intermittently fueled the increased transient eddy heat flux to sustain the SSW over a long time period.The displaced or split SPV centers associated with the SSW played crucial roles in substantially intensifying the tropospheric circulation anomalies and moving the jet stream to the far south to cause cold air outbreaks to a rarely observed extreme state.The results have significant implications for increasing prediction skill and improving policy decision making to enhance resilience in“One Health,One Future”.  相似文献   

20世纪90年代华北大暴雨过程特征的分析研究   总被引：44，自引：6，他引：38  

孙建华  张小玲  卫捷  赵思雄 《气候与环境研究》2005,10(3):492-506

首先对1960～1999年的华北夏季暴雨过程进行了统计分析,之后,又进一步对1990～1999年造成夏季特大暴雨过程的天气形势进行了分型研究.结果表明,从20世纪60年代到90年代夏季每10年发生的暴雨和大暴雨次数基本相当,40年中山西和河北的北部暴雨发生次数在20次以上,沿海地区暴雨发生次数为60～100次.1990～1999年的6～8月华北地区发生大暴雨共39天,大体可分为5型:1型为台风与低槽(低涡)远距离相互作用;2型为低涡(登陆台风)与西风槽相互作用;3型为登陆台风北上受高压阻挡停滞;4型为低涡暴雨;5型为暖切变暴雨.其中,台风和低涡是主要影响系统.最后,对北京夏季的暴雨过程也进行了统计和分型研究.40年中有7年未发生暴雨,而最多的年份发生了5次,存在很明显的年变化.研究表明,尽管北京暴雨具有华北暴雨的共同特征,但也有北京地区的特点,如以暴雨频次而言,最多的是低涡暴雨,其次是台风与低槽(低涡)相互作用型.另外,低槽冷锋暴雨也是一类值得关注的系统.  相似文献   

2009年7月20-22日牡丹江强降雨分析     

宋涛  路平平  龙妍妍 《黑龙江气象》2012,29(1):10-12,36

利用地面、高空观测资料,分析了2009年7月20-22日牡丹江地区的强降雨天气形成原因。此次强降雨主要由东北冷涡配合低空急流共同作用产生,东北冷涡使大气低层辐合、高层辐散,其产生的抽气机效应使上升运动加强;低空急流为降雨提供了充沛的水汽输送。此次强降水,日本数值预报产品预报出了降水中心,与实况比较吻合。研究结果对提高东北冷涡影响下的牡丹江地区强降水预报具有一定指导作用。  相似文献   

THE TOPOGRAPHIC PARAMETER SENSITIVITY TO VORTICITY PROPAGATION AND TYPHOON TANGENTIAL VELOCITY CHANGES     

余锦华 《热带气象学报(英文版)》2005,11(1):31-41

1 INTRODUCTION Being one of the important factors that govern the track and intensity change of the tropical cyclone (TC) [1, 2], topographic features are closely related with topographic parameters and the speed of latitudinal flows. As shown in a statistical study by Brand et al., with its passage through the islands of the Philippines, the TC begins to decrease the mean maximum surface wind speed from 47 m/s to 45 m/s 4 hours before reaching the Philippines. They also find that when …  相似文献   

青岛区域性低涡暴雨的气候特征及预报   总被引：1，自引：0，他引：1  

凌艺  黄明政  李斌  刘秀珍 《气象》2005,31(5):66-69

对青岛1961～2002年的区域性暴雨个例(3个以上基本测站出现≥50mm降水)进行了分析,指出西南涡、西北涡以及切变涡是造成青岛区域性暴雨最主要的影响系统,其路径不同,所产生暴雨的区域及范围不同,急流的位置及动向和切变线位置是判断暴雨落区的重要因素。  相似文献   

北京西山水峪复合型旋扭构造研究   总被引：1，自引：0，他引：1  

杜子图  李东旭  高德臻 《地质力学学报》1995,1(3):65-71

以北京西山水峪为中心有3条弧形断裂,总体呈涡轮状,且都具有压扭性特征,外旋呈逆时针扭动。组成这个旋扭构造的结构面产状不规则,力学性质较复杂,不易辩认。通过构造复合系统分析,查明该旋扭构造的旋回面大都是追踪早期不同系统、不同性质结构面归并复合的结果,为燕山期新华夏系SN向对扭构造应力场的派生产物。   相似文献   

Dynamic loads on submerged bodies in a viscous numerical wave tank at small KC numbers     

V. Armenio 《Ocean Engineering》1998,25(10):881-905

In this paper, an improved version of the MAC method (SIMAC), recently developed at the University of Trieste, is employed for the study of the wave generation and propagation into a numerical wave tank and for the evaluation of dynamic loads over submerged fixed bodies.In the first part of the work, a numerical wave tank was developed. A pneumatic wave-maker at the left-hand side of the tank was implemented by the use of a pressure perturbation at the free surface. The pressure varies in time with a sinusoidal law. Grid sensitivity tests, checks on mass conservation and the Fourier analysis of the waves which propagate in the tank showed the effectiveness of SIMAC in treating such problems. The wave-maker was then calibrated.In the second part of the work, the dynamic loads over submerged square and rectangular cylinders were evaluated. The time records of the horizontal and vertical forces which act over the body were then treated using the Morison equation in order to derive the inertial and damping coefficients. The analysis was carried out for KC numbers ranging between 0.447 and 3.58. Numerical results satisfactorily tallied with experimental data. The analysis of the velocity field near the body evidenced the influence of vortex generation and vortex shedding on the coefficients of inertial forces.  相似文献   

一次初春东北冷涡的结构特征及其降水成因          下载免费PDF全文

刘丹玲  王黎娟 《大气科学学报》2022,45(3):456-468

利用ERA-Interim逐日再分析资料及中国753站逐日降水资料,对2008年3月23—28日的东北冷涡天气过程进行诊断分析,并探讨了冷涡降水的主要影响因子。结果表明：1）与夏季冷涡过程不同,此次初春冷涡过程高层环流场由经向环流向纬向环流转变;冷涡发展初期,经向环流的建立使得冷涡向南移动,而成熟阶段冷涡后部的低槽引导冷空气向冷涡输送,导致了冷涡环流的维持。2）亚欧大陆上空强阻塞形势的发展是初春东北冷涡形成的关键因子;乌拉尔山和鄂霍次克海阻塞高压分别受到前期北大西洋和热带太平洋海温异常的调控,为冷涡向南发展维持提供了有利的环流背景,并影响了高低空急流的配置,有利于冷涡降水的形成。3）涡度场和温度场的高低空配置使得东北冷涡发展成深厚的环流系统,干侵入对冷涡的形成和维持同样有重要作用。冷涡环流的发展为东北地区降水提供了有利的水汽和垂直运动条件,冷暖平流交汇引起的锋面过程则促进大范围降水的形成。  相似文献   

青藏高原低涡研究的回顾与展望   总被引：7，自引：0，他引：7  

刘晓冉  李国平 《干旱气象》2006,24(1):60-66

青藏高原低涡是青藏高原地区特有的产物,是夏季高原上的主要降水系统,而东移出高原的低涡,又往往引发青藏高原下游地区一次大范围的灾害性天气过程。全面回顾了20世纪70年代后期以来,青藏高原气象学研究领域中有关高原低涡的研究进展,按天气学、动力学和数值模拟3方面对有关研究进行了分类,简要总结了各类研究涉及的重要问题及主要成果。在此基础上分析了存在的主要问题,展望了今后高原低涡研究的重要方向和基本趋势。  相似文献   

VORTEX MOTIONS IN THE ATMOSPHERIC CONVECTIVE BOUNDARY LAYER     

桑建国  张治坤 《Acta Meteorologica Sinica》1999,(3)

Large vortices with scales ranging from hundreds meters to tens of kilometers are generallyfound in the atmospheric convective boundary layer(CBL).These vortices play important roles in the vertical transport of momentum,heat,water vaporand other tracers in the boundary layer.On the basis of the view of interaction between theconvection in CBL and the gravity waves in the upper stable layer the authors developed aconvection-wave theory on the formation of large vortices.According to the theory thewavenumber spectrum of the large vortices mainly depends on the atmospheric conditions in bothof the upper and lower layers,such as wind speed,wind direction shear,stratification as well astemperature jump.In the present paper satellite image and weather data in a case of cold air outbreak over warmocean are analyzed to study every stage of the convective processes,such as cloud street,convective cell as well as their transformation.According to the theory the wavenumbercompositions for cloud street and convective cell are calculated,respectively,on the basis of theatmospheric conditions at every stage.The distributions of vertical motions,convergent band anddisturbed interface are obtained and compared with the cloud patterns in the convective processes.Thus the study seems to offer a likely explanation for the origin of large vortices in CBL.  相似文献