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1.
CHAO Jiping 《Acta Meteorologica Sinica》2001,15(1):40-48
Some dynamic constrains in the process of the tropical baroclinic geostrophic adjustment are discussed.The dispersion equation of three-dimensional inertia-gravitational wave and the equation of temporal conservation of potential vorticity are given,without considering the gradient of planetary potential vorticity.It indicates that the motions will be horizontal,meaning that Taylor-Proudman theorem is still right for tropics.At the same time,the semi-geostrophic balance is easier to appear in the tropical belt.Therefore the motions are generally horizontal and non-divergent,but still are stratified after the geostrophic balance establishes. 相似文献
2.
热带地转适应运动的动力学基础 总被引：3，自引：1，他引：2
文中讨论了热带斜压大气地转适应过程中的若干动力学约束关系 ,在不考虑行星位势涡度梯度的前提下给出了三维重力惯性波的频散方程、位势涡度时间不变式。在这基础上指出由于 Taylor- Proudman定理成立 ,运动将趋于水平化。同时指出 ,在热带纬圈半地转平衡更易出现。地转适应后的运动 ,一般是水平无辐散的 ,虽然垂直运动趋于零 ,但物理场随高度仍然有变化 ,即是层结的。 相似文献
3.
The mesoscale balance and imbalance and the corresponding potential vorticity inversion from the view of helicity 
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下载免费PDF全文 The static balance and the geostrophic balance are the common balances in meteorology.All the synoptic systems and most of the mesoscale systems satisfy the above two balances.However,due to the strong convection and non-geostrophic feature,many mesoscale systems usually present as static imbalance,and the quasi-geostrophic approximation is no longer attainable.This paper tried to find out a kind of balance that exists for mesoscale convective system.To do this,the concrete mathematics definitions for balance and imbalance equations were defined.Then,it is proposed that the new balance equation should include the divergence,vorticity,and vertical motion simultaneously,and the helicity equation was a good choice for the basis.Finally,the mesoscale balance and imbalance equations were constructed,as well as a new balance model that was based on the helicity,horizontal divergence,vertical vorticity,continuity,and thermal dynamic equations under same approximations.Moreover,the corresponding potential vorticity(PV)inversion technique was introduced.It was pointed out that by using the PV conservation and the potential temperature conservation,the flows of the mesoscale balance model can be deduced,and their comparison with the real fields would give the degree of the imbalance. 相似文献
4.
本文采用多时间尺度方法分析热带大气的大尺度运动,得到了三个阶段的运动性质。结果表明,热带大尺度大气运动与中纬度大尺度大气运动一样,具有双适应现象,即第一阶段由于重力波频散,产生了地转适应;第二阶段由于长波频散,产生了位涡适应。 同时指出,运动的三个阶段的演变过程,可以统一为位势涡度适应过程,这是一种非线性过程,而地转适应是位涡适应的初级阶段。 相似文献
5.
基于螺旋度的中尺度平衡方程及非平衡流诊断方法 总被引：7，自引：5，他引：7
在回顾大尺度准地转平衡理论、各种平衡方程、平衡模式及非平衡流诊断工具的基础上,对平衡方程、非平衡方程给出了具体的定义.并在此基础上,进一步考虑中尺度强对流天气系统的特征,指出中尺度也有平衡运动的存在.但是由于中尺度对流系统中强烈的辐散风效应以及不可忽略的垂直运动的作用,以散度方程为基础的各种近似平衡方程不足以描述中尺度强对流天气系统的平衡运动,进而提出了从能够同时考虑旋转、辐散及垂直运动作用的螺旋度方程出发,寻找中尺度的平衡方程.在所得的平衡方程基础上,给出了相应的平衡模式和非平衡方程.并进一步将非平衡方程分解,用来诊断非平衡过程的平衡破坏和平衡恢复两个阶段,同时将它们与水平螺旋度和垂直螺旋度联系起来. 相似文献
6.
覃皓 《沙漠与绿洲气象(新疆气象)》2024,18(2):68-75
利用常规观测、卫星数据及ERA5再分析数据,从动力和热力角度对引发2020年5月24-25日广西北部暴雨过程的低涡发展维持机制进行了诊断分析。结果表明：低涡在滇黔桂交界一带生成,随后逐渐发展东移,对流云团及降水落区主要分布在低涡东侧及南侧。涡度方程诊断表明,低涡的发展维持主要受涡度平流项和水平散度项影响。水平风场对涡度的输送使得局地涡度减小,而水平风场的辐合效应使得局地涡度增大。将原始风场分解为地转风和非地转风分量后发现,非地转风分量主导了局地涡度的变化,非地转风水平散度项正贡献最大,扭转项次之,两者是造成低涡发展维持的主要原因。在热力作用方面,低涡发展移动过程中对流层中层附近的潜热加热正反馈也有利于低层低涡的发展维持。 相似文献
7.
边界层特征参数对边界层顶垂直速度的影响 总被引：1，自引：1，他引：1
本文从正斜压及有层结时的边界层相似理论及阻力定律出发，由边界层顶垂直速度与地面湍应力的关系求出了层结、粗糙度、它们的水平梯度及地转风的水平梯度、斜压性对w的影响的解析式，可用于模式计算。计算结果表明层结影响可使w差1-２个量级，不稳定时粗糙度影响也使w差几倍。除地转涡度决定w外，地转风、层结稳定度和粗糙度及其水平梯度也起了重要作用，还讨论了斜压性的影响。 相似文献
8.
With the Ekman momentum approximation,the influence of atmospheric baroclinity on the dynamics of boundarylayer is studied.Some new results are obtained.These results show that the atmospheric baroclinity plays an importantrole in altering the horizontal velocity of Ekman boundary layer and its angle with the horizontal wind velocity compo-nent near the surface.There are three different physical factors affecting the nonlinear Ekman suction,the vertical mo-tion at the top of boundary layer:first,barotropic geostrophic relative vorticity at the ground;second,the thermal windvorticity induced by the baroclinity;and third,the nonlinear interaction between the barotropic geostrophic relativevorticity and the baroclinic thermal wind vorticity.These results may provide a better physical basis for theparameterization of boundary layer and the interpretation of the numerical modeling results. 相似文献
9.
The breakdown and foundation of geostrophic balance is one of the important movements inthe mid-and high-latitude atmosphere and oceans.In the tropical area,the value of Coriolis pa-rameter is so small that it is difficult to satisfy the bi-geostrophic equilibrium between the pressureand velocity fields.However,in the tropical area,the zonal velocity of some motions in the atmo-sphere and oceans is large,so the Coriolis force is not small,geostrophic balance can exist in zonaldirection,i.e.semi-geostrophic balance.Furthermore,in the dominant area of Hadley circulationin the atmosphere or the area near the ocean meridional boundary,the meridional velocity is large,so geostrophic balance can also exist in meridional direction.In this paper,the process of the dis-persion of inertial gravity wave and the foundation of semi-geostrophic balance are first discussed.Second,the adjustment process between the velocity and pressure fields after adaptation is alsoviewed,and the scale criterion of the semi-geostrophic adaptation is discussed,i.e.for the motionwith meridional scale greater than the equatorial Rossby radius of deformation,the velocity andpressure fields after adaptation change to fit the initial pressure field;on the contrary,the fieldschange to fit the initial zonal velocity field,and the strength of the fields after adaptation dependson the zonal scale. 相似文献
10.
A uniform,inviscid,incompressible fluid in a two-dimensional plane(x,z)is considered.Three principles:conservation of potential vorticity,conservation of absolute momentum,andconservation of mass are used for this study.If the initial mass field and the initial wind field donot satisfy geostrophic balance,then through geostrophic adjustment under suitable conditions,the frontogenesis will finally occur.Our work points out that the initial density distribution greatlyinfluences the frontal features.If the stratification in cold air is the same as that in warm air,twofrontogeneses will occur at top and bottom boundaries respectively.If the stratification in cold airis larger than that in warm air,the frontogenesis at the bottom boundary still exists,but the otherat the top boundary disappears.This result makes us further understand the mechanism of thefrontogenesis in the real atmosphere. 相似文献
11.
文中利用时间边界层概念研究了大气运动中的快过程,发现:对的大尺度运动,在时间上可以区分为静力适应过程,地转适应过程及水平无辐散适应过程三个快过程,以静力适应过程为最快,地转适应过程次之,水平无辐散适应过程最慢。对L=L_0的大尺度运动,静力适应过程仍为最快,地转适应过程与水平无辐散适应过程在时间上已难以区分。对L相似文献
12.
Summary Generalized hydrostatic and geostrophic equations can be derived from the equations in the terrain-following framework. The generalized hydrostatic equation permits some non-hydrostatic motions (as obtained from a Cartesian framework) to remain when a non-zero slope exists. Correspondingly, the generalized geostrophic wind permits a horizontal divergent component (in addition to divergence caused by the change of Coriolis parameter with latitude) to occur when the slope angle is not zero.With 1 Figure 相似文献
13.
A DIAGNOSTIC STUDY OF AN EXPLOSIVELY DEEPENING OCEANIC CYCLONE OVER THE NORTHWEST PACIFIC 总被引：1，自引：0，他引：1 下载免费PDF全文
下载免费PDF全文 The vertical motions and secondary circulation of an explosively deepening oceanic cyclone,which oc-curred over the Northwest Pacific Ocean and was in conjunction with 200 hPa-level jet stream and hascentral pressure falls of 33.9 hPa/24h,have been computed from seven-level nonlinear balance model and Saw-yer-Eliassen-Shapiro equation for the transverse ageostrophic circulation.The vertical motions are partitionedinto contributions from large-scale latent heat release,effect of cumulus heating,thermal advection,differen-tial vorticity advection,etc.,while the secondary circulation stream function is partitioned into contributionsfrom geostrophic deformation,transfer of momentum and heat in the area of cumulus and diabatic heating.The principal results are the following.Large-scale latent heat release is very crucial to the explosive de-velopment of cyclones.If there is enough transfer of moisture,the positive feedback process between ascentof air and large-scale heating would work.The cumulus heating and the transfer of momentum and heatin the area of cumulus play an important role during the explosively deepening stage.Thermal advection isthe initial triggering condition for large-scale heating and the conditional instability for the convection ofcumulus. 相似文献
14.
K. Haines P. Malanotte-Rizzoli R.E. Young W.R. Holland 《Dynamics of Atmospheres and Oceans》1993,17(2-3)
Two simple methods for assimilating ocean surface pressure data into a three-layer adiabatic primitive equation model are tested and compared using a twin-experiment approach. One of the methods is based on a recently presented direct insertion scheme using a quasi-geostrophic model. The method explicitly avoids making changes to the potential vorticity fields in the lower layers and the vertical current structure after assimilation is determined by this criterion. The modification required for a primitive equation framework are discussed and a comparison is made with the more familiar ‘nudging’ method of assimilation. We use root mean square errors to quantify the response of the model to the assimilation of a single complete surface pressure field and also to repeated or intermittent data available every 20 days for a period of 1 year. The two methods are almost equally effective in the short term, although the direct insertion scheme appears to be more effective in the longer term. It is suggested that this is because insertion maintains a geostrophic balance at all levels and thus avoids the generation of internal gravity waves which are needed when nudging is used to restore geostrophic currents in the deeper layers. 相似文献
15.
A uniform,inviscid,incompressible fluid in a two-dimensional plane(x,z)is considered.Three principles:conservation of potential vorticity,conservation of absolute momentum,and conservation of mass are used for this study.If the initial mass field and the initial wind field do not satisfy geostrophic balance,then through geostrophic adjustment under suitable conditions,the frontogenesis will finally occur.Our work points out that the initial density distribution greatly influences the frontal features.If the stratification in cold air is the same as that in warm air,two frontogeneses will occur at top and bottom boundaries respectively.If the stratification in cold air is larger than that in warm air,the frontogenesis at the bottom boundary still exists,but the other at the top boundary disappears.This result makes us further understand the mechanism of the frontogenesis in the real atmosphere. 相似文献
16.
Interaction of typhoon and mesoscale vortex 总被引：15，自引：1，他引：14
Under two types of initial tropical cyclone structures that are characterized by high and low vorticity zones, four sets of numerical experiments have been performed to investigate the interaction of a tropical cyclone with an adjacent mesoscale vortex (MSV) and its impact on the tropical cyclone intensity change,using a quasi-geostrophic barotropic vorticity equation model with a horizontal resolution of 0.5 km. The results suggest that the interaction of a tropical cyclone characterized by a high vorticity zonal structure and an MSV would result in an intensification of the cyclone. Its central pressure decreases by more than 14 hPa. In the process of tile interaction, the west and middle segments of the high vorticity zone evolve into two peripheral spiral bands of the tropical cyclone, and the merging of the east segment and the inward propagating MSV forms a new vorticity accumulation area, wherein the maximum vorticity is remarkably greater than that in the center of the initial tropical cyclone circulation. It is this process of merging and strengthening that causes a greater pressure decrease in the center of the tropical cyclone. This process is also more complicated than those that have been studied in the past, which indicated that only the inward transfer of vorticity of the MSV can result in the strengthening of the tropical cyclone. 相似文献
17.
Application of Nonlinear Balance Scheme in Three-Dimensional Variational Data Assimilation 总被引：1，自引：1，他引：1 下载免费PDF全文
下载免费PDF全文 The dynamical constrains in three-dimensional variational data assimilation are discussed when consid- ering the impact of stream divergence and convergence on the pressure and wind fields.For the analysis of severe tropical cyclone,frontal structures,and other rapidly changing structures,the geostrophic balance and linear balance cannot properly represent the relationship between wind and pressure fields.However,the nonlinear balance incremental equation takes into account the information of flow-dependent background, and makes response to the flow-dependent background covariance in the 3D-Var system.Results indicate that the application of the nonlinear balance equation to 3D-Var system improves the quality of severe trop- ical cyclone assimilation system,which has some positive effects on intensity prediction of tropical cyclones. 相似文献
18.
1. IntroductionMuch attention has been paid to the role playedby diabatic heating in the genesis and intensificationof tropical cyclone (TC). Based on a two-dimensionalprimitive equation model, Li (1984) proposed that theevolution of TC should be different if the maximumheating appears at different height. Yang et al. (1995)found that abrupt intensification of TC at the mid-latitudes is closely related to the vertical structure ofconvective heating. May and Holland (1998) suggestedthat the… 相似文献
19.
理想基流中大气波动多折射的数值试验 总被引：3，自引：2，他引：1
利用含非绝热加热的准地转正压涡度方程全球谱模式,采用４种热带海表温度异常作为热源和１６种理想基流,进行了理想基流中大气波动多折射的数值试验,积分时间为３０ｄ。得到：热源所激发的扰动通常能产生二支或三支波列,并由第一支波列分支出第二,三支波列,或第二支分支出第三支波列;对于有些基流,第一支波列维持两周或更长时间后消失,而留下其他波列;第二支波列往往最强,对于某些基流,两支流列有汇合聚集的趋势。 相似文献
20.
Using a barotropic, steady and linearized vorticity equation and using 250 hPa observed basic flow and global divergence field from the active summer monsoon phase (00 GMT 26 June－12 GMT 29 June) 1979, the dynamical effects of linear absolute vorticity advection, vorticity generation due to divergence and vorticity dissipation due to frictional damping have been tested to understand their influence on Southern Asiatic High (SAH). The key experimental results are: (1) The SAH, one of the major planetary-scale disturbances, is generated from the upper basic flow by the forcing of the upper tropospheric divergence over southeast Asia during the active summer monsoon phase. (2) Linear absolute vorticity advection and frictional damping of vorticity play an important role in the determination of the location of the SAH. (3) The destruction and recovery of planetary-scale geostrophic balance is an important mechanism for the west-east oscillation of the SAH. 相似文献