全国各省市气象科技期刊文章摘编（38）

1位涡理论及其应用 《气象》2010年第3期 寿绍文 南京信息工程大学210044 摘要：位涡是近代天气动力学的重要概念之一。本文主要对位涡理论的一些要点,包括位涡的定义、特性、分析方法、位涡思想、位涡反演、湿位涡以及位涡理论的发展和应用等作了介绍。位涡已经成为天气动力学领域中的重要研究方法之一。     

位涡反演理论在台风领域中的应用研究进展

位涡作为一个综合反映流体动力学和热力学性质的物理量,受到气象学者的广泛关注,位涡反演理论逐渐成为台风研究的重要方法之一。在简要回顾近几十年来位涡反演理论研究进展的基础上,综述了位涡反演理论在台风领域中的应用进展情况,讨论了位涡反演理论应用时可能存在的问题,即位涡平均态求取、近地面摩擦作用以及位涡反演平衡条件等都可能影响反演效果,并对位涡反演理论的应用前景作了展望。     

位涡及位涡反演

对位涡概念发展史进行了总结并给出位涡反演原理 ,讨论了不同近似模式的位涡表达式及其拉格朗日守恒形式 ;对位涡特性研究方面的新成果作了总结 ;考察大量应用实例并指出存在的不足 ;最后对应用前景作了展望     

能量位涡在雷雨大风天气诊断分析中的应用

从大气基本运动方程及大气总能量概念出发,提出将大气动力学与能量天气学相结合的物理量——干能量位涡与湿能量位涡,并确定其守恒性.通过分析发现,以静力温度表达的能量位涡数学计算更方便,物理意义更明确.以2007年湖北的一次典型雷雨大风天气为例,对雷雨大风天气用能量位涡进行诊断分析.结果表明:本文提出的干能量位涡与湿能量位涡可以较好地预示雷雨大风天气,高空干能量位涡的增强与向下发展使对流层中下层不稳定能量增大,有利于雷雨大风天气发生;低层湿能量位涡的不稳定能量高值区与斜压系统耦合时预示该区域将有雷雨大风发生.     

位涡诊断在黄土高原强对流风暴预报中的应用

利用位涡理论,对2004年6月15~16日宁夏、内蒙、陕西、山西和河南出现大范围的强对流风暴和局地冰雹天气过程作了诊断分析。个例分析发现,干位涡空间结构表现为:从风暴区下游到风暴区形成随高度向西倾斜的大值正位涡柱,风暴区形成对流层高层大值正位涡中心和对流层中低层伴有位涡梯度增强的位涡等值线密集区的叠置。对流层低层干位涡场特征表现为,风暴区形成干位涡等值线密集区和风场切变的耦合。对流层低层湿位涡场特征表现为,风暴区形成湿位涡正压项小于0对流不稳定舌和湿斜压中心以及湿位涡斜压项等值线密集区的耦合。风暴发生前,对流层中层500hPa河套生成经向位涡等值线密集区,500hPa蒙古地区强偏北气流中同时出现正位涡扰动和指向河套的正位涡平流,对黄土高原大范围强对流风暴的发生有指示意义。     

位涡源汇和位涡环流及其天气气候意义

在扼要回顾地表位涡研究进展的基础上,本文介绍了复杂地形下的位涡及位涡制造的计算及近年来关于位涡源汇和位涡环流(PVC)的研究进展,侧重介绍青藏高原表层位涡的特殊性及其对天气气候的重要影响。阐明对于绝热和无摩擦大气运动,由于位涡本身的结构重组(位涡重构)可以引起垂直涡度的发展,在夏季可以激发高原涡形成,冬季使青藏高原东部成为重要的表面涡源。基于导得的包括非绝热加热作用的、与等熵面的位移相联系的垂直运动(ω_ID)方程,进一步阐明青藏高原制造的正位涡沿西风气流东传会引起下游地区低空气旋性涡度、偏南风、和上升运动发展,导致位涡平流随高度增加,激发极端天气气候事件发生发展。指出青藏高原地表加热和云底的潜热释放的日变化显著地影响着地表层位涡的日变化,导致青藏高原的低涡降水系统多在午后至夜间发生发展。证明与传统的青藏高原感热加热指数相比,青藏高原地表层位涡指数能够更好地刻画关于降水的季节变化,与亚洲夏季风降水相关更密切。本文还简单介绍了PVC的概念。指出由于区域边界面的PVC的辐散辐合的变化直接与区域位涡的变化相关联,为保持北半球位涡总量的相对稳定,跨赤道面上的PVC变化与地表...     

位涡对一次暴雨过程的诊断分析

根据位涡理论分析了1999－06－15～16日江苏和安徽的一次大暴雨过程，结果表明，位涡中的正压位涡项MPV1的正负和暴雨的强弱有较明显的关系，斜压位涡项MPV2的大小也和暴雨有着较好的对应关系。     

一次爆发性气旋的发展与湿位涡关系的研究

通过对一次陆地爆发性气旋的数值模拟与湿位涡的诊断分析发现，气旋的爆发与湿位涡的平流关系密切，气旋的发展并不是在湿位涡中心位于气旋上空时才开始，而是当湿位涡中心位于气旋的后部，并在200hPa对下有明显的倒圆锥形下伸区时，才有利于气旋的发展。当湿位涡中心位于气旋上空时，气旋发展开始减慢。湿位涡局地变化的大小与水平方向位涡梯度的大小有关。湿斜压位涡负值区的上下贯通与气旋发展也有明显的关系。     

关于等熵位涡应用的一点认识

位涡、湿位涡及其守恒开启了(湿)位涡理论的较广泛应用,使(湿)位涡成为天气系统、天气现象演变的重要诊断物理量,能有效解释一些天气系统、天气现象的演变。为合理应用(湿)位涡及等熵位涡思维,简单分析了气象常用坐标中位涡、湿位涡表达式的限制性条件,强调此条件与(湿)等熵坐标成立的条件相同,指出z 坐标(湿)位涡与p、θ(θse)坐标(湿)位涡存在物理差异。在θ(θse)坐标中,气块的水平速度是相对水平面(地面)的移动速度,而非气块沿着等θ(θse)面的移动。在(湿)等熵位涡分析中,(湿)等熵位涡强度的变化,是平流、垂直输送以及非绝热过程的综合作用,不能简单归因为只由高层的(湿)等熵位涡异常向中低层传输、或中低纬的(湿)等熵位涡异常向高纬传送所造成。     

一次西南涡暴雨的位涡分析

利用NCEP提供的FNL再分析资料对2013年5月25—26日发生在我国中东部西南涡暴雨过程的初期阶段进行了位涡分析,结果表明:高原槽附近异常高位涡,促进了低层西南涡前期的发展,这对西南涡前期的预报有很好指导意义;西南涡发展前期,强降雨中心湿位涡正压子项自低层至高层呈现出"负—正"的分布特征,湿位涡斜压子项在中低层有强负值中心,反映出低层对流不稳定和垂直风切变对于对流性降水的促进作用;西南涡发展阶段,湿位涡正压子项正值中心呈现出倾斜漏斗状,斜压子项在降雨中心低层出现了强负值中心;强降水中心与低层扰动湿位涡负值有较好的对应关系,对于强降雨落区的预报提供了一种参考。     

ANALYSIS OF EFFECT OF ENVIRONMENTAL POTENTIAL VORTICITY LOCATED AT SOUTH EDGE OF SOUTH ASIA HIGH ON INTENSIFICATION OF TROPICAL CYCLONES

The NCEP 1°×1°reanalysis of June-to-September dataset between 2002 to 2009 is used in this study to conduct statistical analysis of the relationship between the environmental potential vorticity(PV)on 150 hPa located at the south edge of South Asia High(SAH)and TCs making landfall.The results show that 23 of the TCs are affected by the PV on 150 hPa located at the south edge of SAH between 2002 to2009,and three TCs'center pressure decline after the high-value environmental PV moves to the center of the TCs.These three TCs are Senlaku(0216),Bilis(0604)and Linfa(0903).Through diagnostic analysis from the viewpoint of isolines,we determined the relationship between the intensification of these TCs and the PV anomaly at high levels;the isentropic surface is close to the high level’s PV anomaly under the influence of the 150-hPa PV anomaly,leading to the decline of isentropic surfaces on both sides of the PV anomaly.Then the warm core of the middle and high levels of the TC strengthens and PV increases at the middle level,and both of them are beneficial to the reinforcement of the cyclonic vorticity in the low level.As a result,the center pressure of the TC declines.According to Wu’s theory of Slantwise Vorticity Development(SVD),the incline of the isentropic surfaces leads to the development of vertical vorticity,contributing to the vertical motion and the release of the latent heat.Then the warm core of the TC strengthens and the TC strengthens,too.Otherwise,piecewise PV inversion also shows that the high-level PV influences the mid-level more than the low level.     

ON THE MAINTENANCE OF BLOCKING ANTICYCLONES OF NORTHERN HEMISPHERE—PART I:QUASI-GEOSTROPHIC POTENTIAL VORTICITY ANALYSIS

Four observed blocking anticyclones in different regions of the Northern Hemisphere are in-vestigated.Analyses show that there exist distinct differences in the maintenance of the time-meanquasi-geostrophic potential vorticity(PV)low in 300 hPa within blocking areas.In two Pacificblocking cases,the PV advection by time-mean flow tends to flow the PV low to northwestern partof the blocking highs,and thus is beneficial to the maintenance of the blockings'strength.Thetransfer by transient eddies acts to balance the effect of the time-mean flow.In the Atlantic andAlaska blocking cases,however,the advection of mean flow tends to flow the PV low eastward.The PV transfer by transient eddies acts to flow potential vorticity low to the western part of theblocking ridges and also to balance the time-mean flow's effect.Thus,in the latter two cases,it isthe transfer by the transient eddies that acts to maintain the blockings.     

ON THE MAINTENANCE OF BLOCKING ANTICYCLONES OF NORTHERN HEMISPHERE-PARTⅠ:QUASI-GEOSTROPHIC POTENTIAL VORTICITY ANALYSIS

Four observed blocking anticyclones in different regions of the Northern Hemisphere are investigated.Analyses show that there exist distinct differences in the maintenance of the time-mean quasi-geostrophic potential vorticity(PV) low in 300 hPa within blocking areas.In two Pacific blocking cases,the PV advection by time-mean flow tends to flow the PV low to northwestern part of the blocking highs,and thus is beneficial to the maintenance of the blockings'strength.The transfer by transient eddies acts to balance the effect of the time-mean flow.In the Atlantic and Alaska blocking cases,however,the advection of mean flow tends to flow the PV low eastward.The PV transfer by transient eddies acts to flow potential vorticity low to the western part of the blocking ridges and also to balance the time-mean flow's effect.Thus,in the latter two cases,it is the transfer by the transient eddies that acts to maintain the blockings.     

北半球阻塞高压的维持Ⅰ:准地转和Ertel位涡分析

从北半球不同地区的４个阻塞高压个例，研究了阻塞高压维持机制及其地域性差异。对阻塞高压区域３００ｈＰａ时间平均准地转让涡低值区的维持机制的分析表明，该位涡低值区的维持机制存在显著的地域性差异。其中，在２个太平洋阻高个例中，时间平均流的位涡平流使低位涡向阻高西北部输送，从而有利于位涡低值区经向度的维持；时变扰动的位涡输送则有抵消平均流作用的倾向，从而对位涡低值区的维持起耗散作用。在大西洋和东亚阻高个例中，平均流的位涡平流使低位涡区向东移动，而时变扰动的位涡输送则有抵消平均流位涡平流的作用，从而有利于位涡低值区在原地稳定维持。以上主要是相对涡度输送的差异所致。等熵面Ｅｒｔｅｌ位涡分析表明，阻高区域３３０Ｋ时间平均等熵位涡低值区的维持机制与３００ｈＰａ时间平均准地转位涡低值区的维持机制十分相似，从而表明以上等压面准地转位涡分析可以近似用来代表等熵Ｅｒｔｅｌ位涡分析。     

北半球阻塞高压的维持Ⅱ:瞬变扰动强迫和平均流位涡平流的形成

着重探讨大西洋阻高和东亚阻高个例中瞬变扰动位涡（涡度）输送强迫和太平洋阻高中平均流位涡平流的形成机理。结果表明，扰动在阻高西南部西风分流区因形变而产生的扰动拟能向更小尺度串级过程，并不是扰动位涡输送强迫形成的必要机理。扰－流相互作用在阻高西（北）部非分流气流中也十分显著。数值试验表明，这一相互作用也可能是扰动强迫作用形成的机理。而青藏高原和附近海陆对比的强迫作用则可能是太平洋阻高中平均流的位涡平流形成的重要因素。对比分析表明，阻高维持机制的地域性差别可能与其上游（如青藏高原地区、落基山脉）地形和热源强迫作用不同有关。     

一类高阶位涡反演的算法及其应用

从位涡反演的基本定义和性质出发讨论了它的发展,指出基于非线性平衡(Chamey平衡)来进行位涡反演的局限性,要准确地反演中尺度系统还有待于发展高阶位涡反演算子.文中通过分析位涡反演算子的构造得出,高阶位涡反演算子的存在性问题最终归结为探讨高阶平衡流表达式,即高阶平衡方程的存在性问题.然而,平衡流在运动过程中对惯性重力波...     

A Case Study on a Quasi-Stationary Meiyu Front Bringing About Continuous Rainstorms with Piecewise Potential Vorticity Inversion

A 4-day persistent rainstorm resulting in serious flooding disasters occurred in the north of Fujian Province under the influences of a quasi-stationary Meiyu front during 5-8 June 2006. With 1°× 1° latitude and longitude NCEP reanalysis data and the ground surface rainfall, using the potential vorticity （PV） analysis and PV inversion method, the evolution of main synoptic systems, and the corresponding PV and PV perturbation （or PV anomalies） and their relationship with heavy rainfall along the Meiyu front are analyzed in order to investigate the physical mechanism of the formation, development, and maintenance of the Meiyu front. Furthermore, the PV perturbations related to different physics are separated to investigate their different roles in the formation and development of the Meiyu front. The results show： the formation and persistence of the Meiyu front in a quasi-WE orientation are mainly due to the maintenance of the high-pressure systems in its south/north sides （the West Pacific subtropical high/ the high pressure band extending from the Korean Peninsula to east of North China）. The Meiyu front is closely associated with the PV in the lower troposphere. The location of the positive PV perturbation on the Meiyu front matches well with the main heavy rainfall area along the Meiyu front. The PV inversion reveals that the balanced winds satisfying the nonlinear balanced assumption represent to a large extent the real atmospheric flow and its evolution basically reflects the variation of stream flow associated with the Meiyu front. The unbalanced flow forms the convergence band of the Meiyu front and it mainly comes from the high-pressure system in the north side of the Meiyu front. The positive PV perturbation related to latent heat release in the middle-lower troposphere is one of the main factors influencing the formation and development of the Meiyu front. The positive vorticity band from the total balanced winds is in accordance with the Meiyu front band and the magnitude of the posit     

Impact of Surface Potential Vorticity Density Forcing over the Tibetan Plateau on the South China Extreme Precipitation in January 2008. Part Ⅰ:Data Analysis

The external source/sink of potential vorticity (PV) is the original driving force for the atmospheric circulation. The relationship between surface PV generation and surface PV density forcing is discussed in detail in this paper. Moreover, a case study of the extreme winter freezing rain/snow storm over South China in January 2008 is performed, and the surface PV density forcing over the eastern flank of the Tibetan Plateau (TP) has been found to significantly affect the precipitation over South China in this case. The TP generated PV propagated eastward in the middle troposphere. The associated zonal advection of positive absolute vorticity resulted in the increasing of cyclo-nic relative vorticity in the downstream region of the TP. Ascending air and convergence in the lower troposphere developed, which gave rise to the development of the southerly wind. This favored the increasing of negative meridio-nal absolute vorticity advection in the lower troposphere, which provided a large-scale circulation background conducive to ascending motion such that the absolute vorticity advection increased with height. Consequently, the ascending air further strengthened the southerly wind and the vertical gradient of absolute vorticity advection between the lower and middle troposphere in turn. Under such a situation, the enhanced ascending, together with the moist air transported by the southerly wind, formed the extreme winter precipitation in January 2008 over South China.     

1998年华南大暴雨冷空气活动的位涡场分析

用位涡分析方法讨论了1998年6月18－26日华南特大暴雨期间的冷空气活动特征。结果表明，在持续的东亚阻塞形势下，中高纬冷空气分三次南下，侵入江南至华南地区，造成三次大暴雨过程；南下冷空气在江南一带被来自低纬的西南暖湿气流和东南暖湿气流所切断，形成一高位涡冷空气中心。冷暖空气相互作用的结果使东亚温度场呈现南北暖、中间冷的形式。     

Formation and Replacement Mechanism of the Concentric Eyewall of Super Typhoon Muifa (1109)

Based on high-fidelity numerical simulation by using the Weather Research and Forecast (WRF) model, we analyzed the formation and replacement mechanism of the concentric eyewall of Super Typhoon Muifa (1109) from the aspects of the potential vorticity (PV), dynamic/ thermodynamic structure change, sea surface flux, and water vapor content. Observational data and sensitivity tests were also adopted to verify the results. We found that: (1) The abnormal increase of the PV in the rain zone is mainly due to the condensation latent heat. Sufficient water vapor conditions are beneficial to the formation of the outer eyewall structure, and when the environmental water vapor content is larger, the intensity of the outer eyewall becomes greater. (2) After the formation of the typhoon’s outer eyewall, in the area where the outer eyewall is located, the increase of inertial stability contributes to the decrease of the intensity of the inner eyewall. When the intensity of the outer eyewall is larger, the divergence and subsidence motion in the upper layer of the outer eyewall has a greater weakening effect on the intensity of the inner eyewall. (3) The increase of potential temperature of the outer eyewall is mainly due to the condensation latent heat release and the warming of dry air subsidence motion in the moat area. (4) The increase of sea surface heat flux can prolong the concentric eyewall replacement process.