A Bogus Typhoon Scheme and Its Application to a Movable Nested Mesh Model

ＡＢｏｇｕｓＴｙｐｈｏｏｎＳｃｈｅｍｅａｎｄＩｔｓＡｐｐｌｉｃａｔｉｏｎｔｏａＭｏｖａｂｌｅＮｅｓｔｅｄＭｅｓｈＭｏｄｅｌＷａｎｇＧｕｏｍｉｎ（王国民）（ＤｅｐａｒｔｍｅｎｔｏｆＡｔｍｏｓｐｈｅｒｉｃＳｃｉｅｎｃｅｓ，ＮａｍｉｎｇＵｎｉｖｅｒｓｉｔｙ...     

The East Asian Monsoon Simulation with IAP AGCMs-A Composite Study

Ｔｈｅ　Ｅａｓｔ　Ａｓｉａｎ　Ｍｏｎｓｏｏｎ　Ｓｉｍｕｌａｔｉｏｎ　ｗｉｔｈ　ＩＡＰ　ＡＧＣＭｓ－Ａ　Ｃｏｍｐｏｓｉｔｅ　ＳｔｕｄｙＷａｎｇＨｕｉｊｕｎａｎｄＢｉＸｕｎｑｉａｎｇ（ＩｎｓｔｉｔｕｔｅｏｆＡｔｍｏｓｐｈｅｒｉｃＰｈｙｓｉｃｓ（ＩＡＰ），...     

Behaviour of Coupled Modes in a Simple Nonlinear Air-Sea Interaction Model

Ｂｅｈａｖｉｏｕｒ　ｏｆ　Ｃｏｕｐｌｅｄ　Ｍｏｄｅｓ　ｉｎ　ａ　Ｓｉｍｐｌｅ　Ｎｏｎｌｉｎｅａｒ　Ａｉｒ－Ｓｅａ　Ｉｎｔｅｒａｃｔｉｏｎ　ＭｏｄｅｌＬｉＣｈｏｎｇｙｉｎａｎｄＬｉａｏＱｉｎｇｈａｉ（ＬＡＳＧ，ＩｎｓｔｉｔｕｔｅｏｆＡｔｍｏｓｐｈｅｒｉ...     

Impacts of Land Surface on Climate of July and On set of Summer Monsoon:A Study with an AGCM plus SSiB

ＩｍｐａｃｔｓｏｆＬａｎｄＳｕｒｆａｃｅｏｎＣｌｉｍａｔｅｏｆＪｕｌｙａｎｄＯｎｓｅｔｏｆＳｕｍｍｅｒＭｏｎｓｏｏｎ：ＡＳｔｕｄｙｗｉｔｈａｎＡＧＣＭｐｌｕｓＳＳｉＢ①ＬｉｕＨｕｉ（刘辉）ａｎｄＷｕＧｕｏｘｉｏｎｇ（吴国雄）ＳｔａｔｅＫｅｙＬａｂｏｒ...     

Monsoons over China

ＭｏｎｓｏｏｎｓｏｖｅｒＣｈｉｎａ￥ｂｙＤｉｎｇＹｉｈｕｉ（ＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＭｅｔｅｏｒｏｌｏｇｉｃａｌＳｃｉｅｎｃｅｓ，Ｂｅｉｇｕｇ，Ｃｈｉｎａ）ＡＴＭＯＳＰＨＥＲＩＣＳＣＩＥＮＣＥＳＬＩＢＲＡＲＹ，１６Ｔｈｅｍｏｎｓｏｏｎｏｖｅｒ...     

Estimation of Vertical Wind Field from Single-Doppler Radar RHI Observations

ＥＳＴＩＭＡＴＩＯＮＯＦＶＥＲＴＩＣＡＬＷＩＮＤＦＩＥＬＤＦＲＯＭＳＩＮＧＬＥ－ＤＯＰＰＬＥＲＲＡＤＡＲＲＨＩＯＢＳＥＲＶＡＴＩＯＮＳＰｅｎｇＨｏｎｇ（彭红）ａｎｄＧｅＲｕｎｓｈｅｎｇ（葛润生）ＩｎｓｔｉｔｕｔｅｏｆＭｅｓｏｓｃａｌｅＭｅｔｅｏｒｏｌ...     

Some Aspects of the Characteristics of Monsoon Disturbances Using a Combined Barotropic－Baroclinic Model

ＳｏｍｅＡｓｐｅｃｔｓｏｆｔｈｅＣｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆＭｏｎｓｏｏｎＤｉｓｔｕｒｂａｎｃｅｓＵｓｉｎｇａＣｏｍｂｉｎｅｄＢａｒｏｔｒｏｐｉｃ－ＢａｒｏｃｌｉｎｉｃＭｏｄｅｌ￥Ｎ．Ｒ．ＰａｒｉｊａａｎｄＳ．Ｋ．Ｄａｓｈ（ＣｅｎｔｒｅｆｏｒＡ...     

Multispectrum Method and the Computation of Vapor Equation

ＭｕｌｔｉｓｐｅｃｔｒｕｍＭｅｔｈｏｄａｎｄｔｈｅＣｏｍｐｕｔａｔｉｏｎｏｆＶａｐｏｒＥｑｕａｔｉｏｎ①ＪｉＺｈｏｎｇｚｈｅｎ（季仲贞）ａｎｄＷａｎｇＢｉｎ（王斌）ＬＡＳＧ，ＩｎｓｔｉｔｕｔｅｏｆＡｔｍｏｓｐｈｅｒｉｃＰｈｙｓｉｃｓ，ＣｈｉｎｅｓｅＡ...     

Some Features of a New Generation of Upper-Air Observation System

ＳＯＭＥＦＥＡＴＵＲＥＳＯＦＡＮＥＷＧＥＮＥＲＡＴＩＯＮＯＦＵＰＰＥＲ－ＡＩＲＯＢＳＥＲＶＡＴＩＯＮＳＹＳＴＥＭＨｕａｎｇＢｉｎｇｘｕｎ（黄炳勋）ＩｎｓｔｉｔｕｔｅｏｆＡｔｍｏｓｐｈｅｒｉｃＳｏｕｎｄｉｎｇＡＢＳＴＲＡＣＴＳｏｍｅｆｅａｔｕｒｅｓｏｆ...     

PROGRESSONTIBETANPLATEAUFIELDEXPERIMENT（TIPEX）ANDITSRESEARCHPROGRAMME

ＰＲＯＧＲＥＳＳＯＮＴＩＢＥＴＡＮＰＬＡＴＥＡＵＦＩＥＬＤＥＸＰＥＲＩＭＥＮＴ（ＴＩＰＥＸ）ＡＮＤＩＴＳＲＥＳＥＡＲＣＨＰＲＯＧＲＡＭＭＥ￥ＣｈｅｎＬｉａｎｓｈｏｕ（陈联寿）ａｎｄＸｕＸｉａｎｇｄｅ（徐祥德）ＰＲＯＧＲＥＳＳＯＮＴＩＢＥＴＡＮＰＬＡＴ...     

Midlatitude unstable air-sea interaction with atmospheric transient eddy dynamical forcing in an analytical coupled model

While recent observational studies have shown the critical role of atmospheric transient eddy (TE) activities in midlatitude unstable air-sea interaction, there is still a lack of a theoretical framework characterizing such an interaction. In this study, an analytical coupled air-sea model with inclusion of the TE dynamical forcing is developed to investigate the role of such a forcing in midlatitude unstable air-sea interaction. In this model, the atmosphere is governed by a barotropic quasi-geostrophic potential vorticity equation forced by surface diabatic heating and TE vorticity forcing. The ocean is governed by a baroclinic Rossby wave equation driven by wind stress. Sea surface temperature (SST) is determined by mixing layer physics. Based on detailed observational analyses, a parameterized linear relationship between TE vorticity forcing and meridional second-order derivative of SST is proposed to close the equations. Analytical solutions of the coupled model show that the midlatitude air-sea interaction with atmospheric TE dynamical forcing can destabilize the oceanic Rossby wave within a wide range of wavelengths. For the most unstable growing mode, characteristic atmospheric streamfunction anomalies are nearly in phase with their oceanic counterparts and both have a northeastward phase shift relative to SST anomalies, as the observed. Although both surface diabatic heating and TE vorticity forcing can lead to unstable air-sea interaction, the latter has a dominant contribution to the unstable growth. Sensitivity analyses further show that the growth rate of the unstable coupled mode is also influenced by the background zonal wind and the air–sea coupling strength. Such an unstable air-sea interaction provides a key positive feedback mechanism for midlatitude coupled climate variabilities.

     

用自由模对1998年夏季阻塞形势的诊断分析

签于大气自由模和阻塞高压的重要性 ,首先简要介绍阻塞高压与中国夏季降水的关系及 1998年夏季 5 0 0hPa异常环流场 ;然后利用 2 1波菱形截断的谱方法求出无粘性、无强迫正压涡度方程的自由解 ,即和实际大气流场十分接近的大气自由模 ,并讨论其特征 ;最后利用大气自由模的特征诊断分析了实际大气的环流特征 ,并重点用其分析了 1998年夏季的大气环流异常形势。结果表明大气自由模能很好地反映大气环流大尺度特征 ,而略去了中、小尺度涡旋 ;大气自由模的流场和绝对涡度场之间的散点图反映了 (q ,Ψ )的函数关系是分段线性或非线性的 ,尽管实际流场与绝对涡度场之间的点阵图反映两者之间成不同斜率的线性函数关系 ,但点阵比较发散 ,不能突出某些重要系统 ;1998年夏季实际大气自由模态突出了大气环流的重要特征 ,例如 ,越赤道气流、西风急流、副热带高压、阻塞高压及两极的边界效应等 ;通过自由模态的特征可以识别出纬向流及阻塞高压的持续异常 ,利用自由模的稳定性判断阻塞高压的稳定性 ,不稳定模态可以维持一段较长的时间 ,且由于这些不稳定的模存在 ,才使 1998年 6月中旬到下旬的中高纬阻塞高压稳定维持。     

Dynamical and Thermal Problems in Vortex Development and Movement. Part II: Generalized Slantwise Vorticity Development

The development of vertical vorticity under adiabatic condition is investigated by virtue of the view of potential vorticity and potential temperature (PV-θ) and from a Lagrangian perspective. A new concept of generalized slantwise vorticity development (GSVD) is introduced for adiabatic condition. The GSVD is a coordinate independent framework of vorticity development (VD), which includes slantwise vorticity development (SVD) when a particle is sliding down the concave slope or up the convex slope of a sharply tilting isentropic surface under stable or unstable condition. The SVD is a special VD for studying the severe weather systems with rapid development of vertical vorticity. In addition, the GSVD clarifies VD and SVD. The criteria for VD and SVD demonstrate that the demand for SVD is much more restricted than the demand for VD. When an air parcel is moving down the concave slope or up the convex slope of a sharply tilting isentropic surface in a stable stratified atmosphere with its stability decreasing, or in an unstable atmosphere with its stability increasing, i.e., its stability θ z approaches zero, its vertical vorticity can develop rapidly if its C D is decreasing. The theoretical results are employed to analyze a Tibetan Plateau (TP) vortex (TPV), which appeared over the TP, then slid down and moved eastward in late July 2008, resulting in heavy rainfall in Sichuan Province and along the middle and lower reaches of the Yangtze River. The change of PV 2 contributed to the intensification of the TPV from 0000 to 0600 UTC 22 July 2008 when it slid upward on the upslope of the northeastern edge of the Sichuan basin, since the changes in both horizontal vorticity η s and baroclinity θ s have positive effects on the development of vertical vorticity. At 0600 UTC 22 July 2008, the criterion for SVD at 300 K isentropic surface is satisfied, meaning that SVD occurred and contributed significantly to the development of vertical vorticity. The appearance of the stronger signals concerning the VD and SVD surrounding the vortex indicates that the GSVD concept can serve as a useful tool for diagnosing the development of weather systems.     

CONSERVATION OF MOIST POTENTIAL VORTICITY AND DOWN-SLIDING SLANTWISE VORTICITY DEVELOPMENT*

An accurate form of the moist potential vorticity(MPV) equation was deduced from a complete set of primitive equations.It was shown that motion in a saturated atmosphere without diabatic heating and friction conserves moist potential vorticity.This property was then used to investigate the development of vertical vorticity in moist baroclinic processes.Results show that in the framework of moist isentropic coordinate,vorticity development can result from reduction of convective stability,or convergence,or latent heat release at isentropic surfaces.However,the application of the usual analysis of moist isentropic potential vorticity is limited due to the declination of moist isentropic surfaces.and a theory of development based on z-coordinate and p-coordinate was then proposed.According to this theory,whether the atmosphere is moist-symmetrically stable or unstable,on convective stable or unstable,the reduction of convective stability,the increase of the vertical shear of horizontal wind or moist baroclinity may result in the increase of vertical vorticity,so long as the moist isentropic surface is slantwise.The larger the declination of the moist isentropic surface,the more vigorous the development of vertical vorticity.In a region with a monsoon front to the north and the warm and moist air to the south,or by the north of the front,the moist isentropes are very steep.The is the region most favorable for development of vorticities and formation of torrential rain.For a case of persistent torrential rain occurring in the middle and lower reaches of the Changjiang and Huaihe Rivers in June 11-15,1991,moist potential vorticity analysis,especially the isobaric analysis of its vertical and horizontal components,i.e.MPV1 and MPV2,respectively,is effective for identifying synoptic systems not only in middle and high latitudes,but also in low latitudes and in the lower troposphere.It can serve as a powerful tool for the diagnosis and prediction of torrential rain.     

Caribbean hurricanes: case study of interacting easterly and westerly waves

This observational study considers Caribbean cyclogenesis in the period 2003?C2009. Numerous events are identified from maximum of low-level relative vorticity and rain rate, and a case study is analyzed. Although fast moving tropical cyclones (TC) pose dangers to Caribbean Islands, it is the slower moving TC that inflict flood damage. The Atlantic warm pool enlarges through October as steering winds slacken. African easterly waves move over the warm pool and draw moist unstable air, while near-equatorial Kelvin waves from the Pacific surge into the Caribbean. The westerly flow accelerates around the northern Andes and is drawn into TC Omar 13?C15 October 2008. A combination of warm pool air and cyclonic vorticity provided by transient zonal waves sets off the process of cyclogenesis.     

正压涡度方程中考虑粘性项与平滑过程的一些意见

本文首先讨论了如何依据空间步长来选取平滑系数。其次考虑在涡度方程中加上粘性项后对微分方程解的影响,讨论如何选取适当的粘性系数。第三讨论涡度方程加粘性项后对差分格式计算稳定性的影响,证明了在常用时间中心差分格式中应把粘性项取在第(n-1)时间层,这样计算才是稳定的。反之,如把粘性项取在第n时间层,则差分格式计算不稳定。并且时间向前差的格式在加上粘性项后也可以稳定,但要求的粘性系数过大。最后讨论了用涡度方程作数值预告时加上平滑过程与加上粘性项之间的关系,从计算上看,二者并不等价。但可以把平滑过程与扩散方程类比,以确定适当的平滑系数。     

Vertical vorticity development owing to down-sliding at slantwise isentropic surface

Based upon the conservation of Ertel potential vorticity and moist potential vorticity, a ‘parcel dynamic’ approach is used to investigate the development of vertical vorticity of a parcel which is sliding down a slantwise isentropic surface. An accurate form of the tendency equation of vertical vorticity is deduced to interpret such slantwise vorticity development (SVD). In addition to those dynamic terms in the traditional vertical vorticity equation, the newly developed accurate form includes several thermal terms associated with the changes in stability, vertical wind shear and baroclinity. It is proved that the combinative impacts of these thermal terms on the development of vertical vorticity can be expressed by a succinct theory of SVD. According to this theory, when the horizontal component of potential vorticity and stability possess opposite signs, and the slantwise isentropic surfaces are very steep, the vorticity development of the down-sliding flow at such isentropes can be dramatic. It is also shown that in a convectively unstable and saturated atmosphere, such vorticity development must be accompanied by the development of a low-level jet. Study of a torrential rain process shows that moist potential vorticity analysis is a powerful tool in the study of torrential rain occurrence. Results from the present study are in agreement with the contentions of earlier workers that moist symmetric instability is the cause of some heavy rainbands.     

湿位涡和倾斜涡度发展

从完整的原始方程出发，在导出精确形式的湿位涡方程的基础上，证得绝热无摩擦的饱和湿空气具有湿位涡守恒的特性。并由此去研究湿斜压过程中涡旋垂直涡度的发展。结果表明，在湿等熵坐标中，涡旋的发展与对流稳定度的减少，等熵面上的辐合和潜热的释放有关。由于等熵位涡分析的应用受等熵面倾斜的限制，又进而发展了Ｚ坐标及Ｐ坐标中的倾斜涡度发展理论。指出无论是湿对称不稳定或对流不稳定大气，还是湿对称稳定或对流稳定大气，除对流稳定度的影响外，风的垂直切变的增加或水平湿斜压的增加均能因湿等熵面的倾斜而引起垂直涡度的增长。湿等熵面的倾斜越大，这种由干湿斜压性加强所引起的涡旋发展更激烈。在梅雨锋附近及其南侧暖湿区的北端，湿等熵面十分陡立，是涡旋发展及暴雨发生的重要地区。对１９９１年６月１２—１５日江淮流域暴雨过程的湿位涡分析表明，湿位涡分析，尤其是等压面上湿位涡量ＭＰＶ１和ＭＰＶ２的分析不仅在中高纬有效，在低纬度及低对流层也十分有效，是暴雨诊断和预报的有力工具。     

ON THE BAROTROPIC INSTABILITY OF LARGE SCALE VORTICES*

By using the linearized barotropic vorticity equation in polar coordinates the stability of perturbations on a large scale circular basic flow is transformed into a generalized eigenvalue problem,yielding the relationship between the growth rate of the amplitude of perturbations and the azimuthal wave number. Then, numerical experiments whose integration time is 60 model hours are performed in terms of a quasi-geostrophic barotropic model in Cartesian coordinates using the perturbation stream function field of unstable mode superimposed on a strong and weak circular basic flows as the initial fields. The experimental results reveal that the amplitudes of the initial perturbations in the model atmosphere grow with time. The amplitude of the perturbations superimposedon the strong circular basic flow grows quicker and forms a spiral-band-like structure.     

Nonlinear stability analysis of the zonal flows at middle and high latitudes

An attempt has been made to apply Arnol’d type nonlinear stability criteria to the diagnostic study of the persistence (stability) or breakdown (instability) of the atmospheric flows. In the case of the blocking high, the cut-off low and the zonal flow, the relationships of the geostrophic stream function versus the po-tential vorticity of the observed atmosphere are analyzed, which indicates that Arnol'd second type nonlinear stability theorem is more relevant to the observed atmosphere than the first one. For both the sta-ble and unstable zonal flows, Arnol’d second type nonlinear stability criteria are applied to the diagnosis. The primary results show that our analyses correspond well to the evolution of the atmospheric motions. The synoptically stable zonal flows satisfy Arnol'd second type nonlinear stability criteria; while the synoptically unstable ones violate the nonlinear stability criteria.