Observational and theoretical studies of the moist baroclinic atmosphere

In this paper, the main scientific conclusions of a national wide project of heavy summer rainstorms are presented. The active role of the moisture in the large scale motion of the atmosphere is stressed when the water vapour is saturated. The concept of moist baroclinity is introduced, and moist baroclinic processes are studied. Theoretical results, i. e., moist solenoid, moist available potential energy, moist jet, moist baroclinic instability, etc. are presented. Some observational and numerically experimental results are also shown.     

Adjoint sensitivity study on idealized explosive cyclogenesis

The adjoint sensitivity related to explosive cyclogenesis in a conditionally unstable atmosphere is investigated in this study.The PSU/NCAR limited-area,nonhydrostatic primitive equation numerical model MM5 and its adjoint system are employed for numerical simulation and adjoint computation,respectively.To ensure the explosive development of a baroclinic wave,the forecast model is initialized with an idealized condition including an idealized two-dimensional baroclinic jet with a balanced three-dimensional moderateamplitude disturbance,derived from a potential vorticity inversion technique.Firstly,the validity period of the tangent linear model for this idealized baroclinic wave case is discussed,considering different initial moisture distributions and a dry condition.Secondly,the 48-h forecast surface pressure center and the vertical component of the relative vorticity of the cyclone are selected as the response functions for adjoint computation in a dry and moist environment,respectively.The preliminary results show that the validity of the tangent linear assumption for this idealized baroclinic wave case can extend to 48 h with intense moist convection,and the validity period can last even longer in the dry adjoint integration.Adjoint sensitivity analysis indicates that the rapid development of the idealized baroclinic wave is sensitive to the initial wind and temperature perturbations around the steering level in the upstream.Moreover,the moist adjoint sensitivity can capture a secondary high sensitivity center in the upper troposphere,which cannot be depicted in the dry adjoint run.     

MOIST POTENTIAL VORTICITY DIAGNOSIS OF A MEIYU FRONTAL HEAVY RAIN PROCESS SIMULATION DURING SUMMER, 1991

In this paper,the heavy rain process from June 30 to July 2,1991,has been simulated by MM4.and three-dimensional moist potential vorticity distribution of the simulation results has been calculated.It is shown that moist potential vorticity is an important physical variable to reveal heavy rain structure and dynamic mechanisms.Negative moist potential vorticity corresponds to the Meiyu front-wind shear line system and the negative center corresponds to the heavy rain center.Negative moist potential vorticity mainly attributes to the effects of meridional baroclinic term and convective unstable term.The former is favourable to the maintenance of zonal precipitation and the latter is the mechanism of the heavy rain center propagating along the rain belt.The heavy rain is contributed by the cooperative effects of conditional convective instability,baroclinic instability and upper air inertial instability.     

MOIST POTENTIAL VORTICITY DIAGNOSIS OF A MEIYU FRONTAL HEAVY RAIN PROCESS SIMULATION DURING SUMMER,1991

In this paper,the heavy rain process from June 30 to July 2,1991,has been simulated by MM4.and three-dimensional moist potential vorticity distribution of the simulation results has beencalculated.It is shown that moist potential vorticity is an important physical variable to reveal heavyrain structure and dynamic mechanisms.Negative moist potential vorticity corresponds to the Meiyufront-wind shear line system and the negative center corresponds to the heavy rain center.Negativemoist potential vorticity mainly attributes to the effects of meridional baroclinic term and convectiveunstable term.The former is favourable to the maintenance of zonal precipitation and the latter is themechanism of the heavy rain center propagating along the rain belt.The heavy rain is contributed bythe cooperative effects of conditional convective instability,baroclinic instability and upper air inertialinstability.     

华东地区强对流降水过程湿斜压涡度的诊断分析

湿斜压涡度(Moist Baroclinic Vorticity,MBV)、湿热力斜压涡度(Moist Thermodynamic Baroclinic Vorticity,MTBV)及湿位涡(Moist Potential Vorticity,MPV)是能够完整表征涡度三维信息的物理量,其中MBV代表切变风对湿比容的平流输送作用,MTBV反映了垂直气压梯度、对流稳定度、风垂直切变与湿比容水平梯度之间的耦合效应。本文利用这些物理量对2009年8月17日发生在华东地区的一次强对流降水过程进行了诊断分析。该过程是在高空急流、中层浅槽和低空切变线的密切配合下产生的,共经历了"团状结构—带状结构—团状结构"三个发展阶段。诊断结果表明,MPV、MBV和MTBV的异常值区与降水落区有较好的对应关系;随着强对流降水的发展演变,MPV、MBV和MTBV都产生了相应的变化,MPV、MBV和MTBV对降水和对流系统有追踪指示意义。相对而言,在反映降水强度变化方面,MBV和MTBV比MPV更具优势。     

稳定的和不稳定的斜压行星波

本文采用两层模式,初步地应用“时空同化”的自然观,引进空间不稳定性观点,把空间不稳定性和时间不稳定性结合起来,研究振幅随纬度变化的斜压行星波的存在范围和其稳定性;得出了稳定的和不稳定的斜压行星波及其空间不稳定判据,并对传统的斜压行星波不稳定理论和判据作出鉴定,重新提出了斜压行星波时间不稳定判据,并讨论其物理含义;还得出了高层和低层斜压行星波相互强迫振动的机制以及不同纬度间扰动振幅的关系。     

影响山东的台风暴雨天气的湿位涡诊断分析

应用湿位涡理论 ,对发生在山东境内由台风和台风减弱的低压引发的两场大暴雨过程进行诊断。结果表明 :这两场暴雨都产生在θe 陡立密集区附近 ,θe 陡立密集区附近易导致湿斜压涡度发展 ;对流层中低层MPV1 <0 ,850hPa上MPV2 >0 ,综合反映了暴雨区对流不稳定和斜压不稳定的发展 ;对流层高层高值湿位涡下传 ,有利于位势不稳定能量的储存和释放 ,使降水增幅。     

一次北方春季罕见暴雨天气的湿位涡分析

应用湿位涡理论 ,对 2 0 0 3年 4月发生在山东境内的一次暴雨天气进行诊断。结果表明 :暴雨产生在θe 线陡立密集区附近 ,θe 线陡立密集区附近对流稳定度较小 ,有利于湿斜压涡度发展 ;湿位涡在 70 0hPa上具有MPV1 <0 ,MPV2 >0的特征 ,对流层高层高值湿位涡下传有利于位势不稳定能量的储存和释放 ,也是低涡东移发展为气旋的重要机制。     

湿位涡在广西冰雹大风天气过程诊断分析中的应用

应用湿位涡理论,对2006年4月发生在广西的3次冰雹大风强对流天气过程进行了详细地诊断分析.结果表明:θsc线陡立密集区附近对流稳定度很小,冷空气从高层沿等熵面下滑的过程中绝对涡度增加,导致气旋性涡度的发展加强,为冰雹、大风天气的易发地;强对流天气发生前对流层高层有湿位涡高值中心向下传播,强对流易在正压湿位涡等值线相对密集零线附近和925 hPa上斜压湿位涡负中心附近出现.     

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。     

A MESO-α-SCALE STUDY OF MEIYU FRONT HEAVY RAIN－PART II: THE DYNAMICAL ANALYSIS OF RAIN-BAND DISTURBANCE

The alternating change of the two meiyu front rain-bands caused by the alternating change between the moist potential vorticities is discussed. The main factors of the change of moist potential vorticity are the vertical and horizontal divergence of moist potential vorticity flux as well as the vertical transport caused by the cumulus mass flux. Also discussed is the possibility that the WAVE-CISK conditional symmetric instability in the baroclinic moist atmosphere leads to the forming of the double rain-bands and their roller-shaped circulation features. Theoretical analyses show that the latitudinal disturbance scale-selection by the primitive moisture model of the latent heat release in cumulus convection depends on the stratification instability parameter (Ri number) and viscous coefficient of eddy.     

气旋冷暖区暴雨对比分析

利用常规资料及MM5的模拟分析结果，对山东两次气旋影响产生不同暴雨落区的天气过程进行了对比分析。研究了气旋冷区和暖区暴雨的高低空系统配置、相当位温的水平及垂直分布、垂直运动及散度的垂直分布。结果表明：冷区暴雨具有明显后倾结构和较强斜压锋区，暴雨出现在850hPa θe暖湿舌后部密集区，其垂直运动沿锋面大范围抬升，动力条件更强；而暖区暴雨高低空系统重合，暴雨出现在850hPa θe暖湿舌里。这些特征可为暴雨落区预报提供参考。     

湿位涡分析在河北东北部暴雨预报中的应用

应用湿位涡理论,对2008年6月25日发生在河北省东北部的1次局地暴雨天气进行了诊断分析。结果表明,暴雨产生在θse线陡立密集区附近,θse线陡立密集区附近对流稳定度较小,有利于湿斜压涡度发展,MPVI“高层正值区低层负值区垂直迭加”的配置是暴雨发生、发展的有利形势,暴雨区位于850hPa上MPVI零线附近,湿位涡在850hPa上具有MPV1〈0,MPV2〉0的特征,在夏季可以作为河北省北部预报暴雨的一个有效辅助工具。     

热力强迫对湿斜压大气中南亚高压平衡态的影响

本文基于Lorenz的湿模式,引入地形效应并进行适当简化,在低谱近似下得到了描述大气运动的非线性耗散系统。讨论了在热力强迫与大气环流的非线性相互作用下,湿、斜压大气在参数空间的平衡态与南亚高压的流型分布及其东西摆动。结果表明:南亚高压典型的平衡态流型是西部型、东部型和带状高压,而且东西部流型的转换并非高压中心的连续位移,而是表现为一个高压中心消失后经过流场上的调整重新建立新的高压中心的过程。     

The Role of diabatic heating, torques and stabilities in forcing the radial- vertical circulation within cyclones part iii: case study of lee-side cyclones

１．ＩｎｔｒｏｄｕｃｔｉｏｎＡｎａｇｒｅｅｍｅｎｔｂｅｔｗｅｅｎｔｈｅｓｉｍｕｌａｔｅｄａｎｄ“ｏｂｓｅｒｖｅｄ”ａｚｉｍｕｔｈａｌｙ－ａｖｅｒａｇｅｄｍａｓ－ｗｅｉｇｈｔｅｄｒａｄｉａｌｍｏｔｉｏｎｓｈａｓｂｅｎｅｓｔａｂｌｉｓｈｅｄｆｏｒｔｈｅＯ...     

湿急流的结构及形成过程

利用比较稠密的无线电探空和气球测风观测网,通过对华北夏季一次暴雨过程的三维流场和湿度场的分析,揭示了湿急流的结构和形成过程。湿急流是指低层空气在湿不稳定大气的上升过程中,不断加速形成一支斜穿整个对流层的自下而上的急流。在湿急流附近,凝结饱和区的分布和发展过程,似乎表明水汽在急流形成过程中起了一种主动作用。湿急流在对流层顶附近和副热带急流合併,并使副热带急流的动能增加。这似乎启示,湿斜压过程可能是大气环流中的基本过程之一。     

一次江淮暴雨的数值模拟及暴雨落区的诊断分析

利用MM5模式对2003年7月一次江淮暴雨过程进行了数值模拟,结果表明：MM5对本次暴雨落区的模拟较为成功。应用模拟结果对假相当位温、水汽通量散度、z-螺旋度及湿位涡等几个综合性物理量进行了诊断,得出的主要结论为：本次暴雨发生在高能舌的前部、能量锋区南缘和低空急流左前方三者叠加的区域;水汽通量散度比较好地反映本次暴雨的强度和落区;z-螺旋度不仅能反映降水系统,对降水系统的移动也有预报指示意义;本次暴雨过程中湿斜压性和涡度垂直分量与热力不稳定对湿位涡有同等大小的贡献。     

一个内陆台风的湿有效能量分析

该文利用新给出的公式计算了1981年第8号台风各个时段的湿有效能量(MAE)及其三个分量。结果发现:台风系统是一个高能体，温带气旋阶段系统的MAE比热带台风阶段的MAE大。MAE的变化主要是由于它的正压分量和斜压分量变化引起；在系统降水的不同阶段表现出不同的能量特征。台风暴雨的形成主要靠消耗MAE的斜压分量和对流层下层的层结分量能量。     

梅雨期间次天气尺度扰动的动能平衡

计算了梅雨期间产生暴雨的次天气尺度扰动的动能分布及其乎衡。结果表明:1)在动能计算中不能略去风的散度部分;2)暴雨期间,扰动向周围大气输送动能;3)旋转风的动能产生率为负值,散度风在对流层下层和上层产生动能,两者之和仍是消耗动能。这样,次网格尺度对流在动能平衡中起着重要的作用。即在条件性不稳定的大气中,发展起来的温对流是湿斜压大气中重要的一种过程。上述结果有助于了解扰动的机制和改进数值模式的设计。     

湿大气中低涡暴雨系统发展东移的初步分析

七十年代,谢义炳教授指出:湿大气动力学和干大气动力学特征有明显差异。结合我们的天气实践,注意到经常造成鄂北强降水的西南低涡处于对流层低层,在这一层次内不仅流场辐合明显,而且水汽丰沛,空气为强烈的对流性不稳定,这些因子对低涡的生消移动必然有较大的影响。本文的目的是,引入水汽因子后,通过简化涡度方程在湿斜压大气中的应用,并考虑湿静力稳定度σ_m既为P的函