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1.
西大西洋锋面气旋过程的数值模拟和等熵分析 总被引：15，自引：4，他引：15
文中使用PSU/NCARMM 5非静力数值模式对 1992年 3月 13～ 15日发生在西大西洋上的一次海洋气旋爆发过程进行了 6 0h的模拟 ;基于倾斜涡度发展理论 ,从等熵面倾斜的角度研究了气旋的发生、发展、运动和变化 ,利用高分辨率模拟结果对这次过程进行了分析。模拟结果很好地再现了气旋的发生、移动、加深、气旋的热力结构以及地面环流等特征。其中主要气旋M在6 0h的模拟中共降压 4 5hPa ;第 36～ 4 2时 (模式时间 ) 6h内降压达 12hPa。剖面图及等熵面图分析指出 ,气旋的发生、发展、运动和变化与等熵面或等相当位温面的倾斜密切相关 ,气旋中心总是位于等熵面或等相当位温面近于垂直的对流中性地区 ,这与倾斜涡度发展理论的阐述是一致的。气旋在弱静力稳定度的海洋表面启动发展之后 ,气旋与大尺度环境场相互作用 ,气旋得到迅速发展。“倾斜涡度发展理论”(以下简称SVD理论 )可以很好地解释此次海洋锋面气旋的发展与移动。气旋的发展和移动与等熵面的倾斜密切相关 ,发展期气旋前部及其移动路径前方自组织的斜升气流与倾斜的等熵面相配合 ,共同构成上滑“倾斜涡度发展”(SVD理论的推广 ,以下简称USVD理论 )的必要因子 ,在一定的条件下 (C·D<0 ,CD 为SVD指数 ) ,使得气旋及其前方 ,尤其是移动路径前方出现USVD发 相似文献
2.
S. D. Kotal S. K. Bhattacharya S. K. Roy Bhowmik P. K. Kundu 《Meteorology and Atmospheric Physics》2013,121(3-4):161-179
This study investigates the life cycle of Bay of Bengal cyclone JAL, characterized by a rapid fluctuation in its intensity during 60-h interval. The cyclone JAL underwent a period of rapid intensification during 24-h from 0000 UTC 05 November to 0000 UTC 06 November 2010. It was quasi-static during subsequent 24 h followed by a 12-h period of unusually rapid decay. During the rapid cyclogenesis phase, the system intensified (by 25 kt) from deep depression (DD) to severe cyclonic storm (SCS) and weakened (by 30 kt) from SCS to DD during the 12-h period of rapid cyclolysis. European Centre for Medium Range Weather Forecasts (ECMWF) model analysis field is used to analyze the Q vectors, K index and potential vorticity (PV) to diagnose the life cycle of this unusual cyclone. The analysis reveals that the 500–700 hPa column-averaged Q-vector convergence above the surface cyclone had strengthened and very high values of the K index produced a burst of heavy precipitation during the development stage of the cyclone. The associated latent heat release produced a substantial diabatic positive PV anomaly in the lower and middle troposphere that caused rapid cyclogenesis. The rapid cyclolysis is coincident with the weakening of the upper and lower PV anomalies and the westward shearing of the upper PV from the cyclone centre. Thus, the very latent heat release that assisted the rapid development of the cyclone also played an important role in its subsequent rapid decay. ECMWF model forecast for track and intensity is also verified. 相似文献
3.
Up-sliding Slantwise Vorticity Development and the complete vorticity equation with mass forcing 总被引：16，自引：1，他引：15
The moist potential vorticity (MPV) equation is derived from complete atmospheric equations including the effect of mass forcing, with which the theory of Up-sliding Slantwise Vorticity Development (USVD) is proposed based on the theory of Slantwise Vorticity Development (SVD). When an air parcel slides up along a slantwise isentropic surface, its vertical component of relative vorticity will develop, and the steeper the isentropic surface is, the more violent the development will be. From the definition of MPV and the MPV equation produced here in, a complete vorticity equation is then put forward with mass forcing, which explicitly includes the effects of both internal forcings, such as variations of stability, baroclinicity, and vertical shear of horizontal wind, and external forcings, such as diabatic heating, friction, and mass forcing.When isentropic surfaces are flat, the complete vorticity equation matches its traditional counterpart. The physical interpretations of some of the items which are included in the complete vorticity equation but not in the traditional one are studied with a simplified model of the ChangjiangoHuaihe Meiyu front. A 60-h simulation is then performed to reproduce a torrential rain event in the ChangjiangoHuaihe region and the output of the model is studied qualitatively based on the theory of USVD. The result shows that the conditions of the theory of USVD are easily satisfied immediately in front of mesoscale rainstorms in the downwind direction, that is, the theory of USVD is important to the development and movement of these kinds of systems. 相似文献
4.
Vertical vorticity development owing to down-sliding at slantwise isentropic surface 总被引：2，自引：0，他引：2
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. 相似文献
5.
湿斜压性与热带气旋强度突变 总被引：23，自引：2，他引：23
应用湿位涡方程和倾斜涡度发展理论 ,研究了热带气旋内部相当位温结构的演变与其强度突变的可能关系 ,并用一套高分辨率的模拟资料对所得结论进行验证。结果表明 ,由于热带气旋眼壁附近等相当位温面陡立 ,湿斜压性变化所激发的倾斜涡度发展是引起该区域垂直涡度突然增大或突然减小的主要原因。当热带气旋中心附近大部分区域的垂直涡度显著增长时 ,热带气旋就会在整体上表现为爆发性或迅速发展。最后还据此对同心双眼结构的出现和消失如何影响热带气旋强度变化进行了探讨。 相似文献
6.
Shouting Gao Zhemin Tan Sixiong Zhao Zhexian Luo Hancheng Lu Donghai Wang Chunguang Cui Xiaopeng Cui Jianhua Sun 《大气科学进展》2015,32(2):192-205
Progress over the past decade in understanding moisture-driven dynamics and torrential rain storms in China is reviewed in this paper. First, advances in incorporating moisture effects more realistically into theory are described, including the development of a new parameter, generalized moist potential vorticity(GMPV) and an improved moist ageostrophic Q vector(Qum). Advances in vorticity dynamics are also described, including the adoption of a "parcel dynamic" approach to investigate the development of the vertical vorticity of an air parcel; a novel theory of slantwise vorticity development, proposed because vorticity develops easily near steep isentropic surfaces; and the development of the convective vorticity vector(CVV)as an effective new tool. The significant progress in both frontal dynamics and wave dynamics is also summarized, including the geostrophic adjustment of initial unbalanced flow and the dual role of boundary layer friction in frontogenesis, as well as the interaction between topography and fronts, which indicate that topographic perturbations alter both frontogenesis and frontal structure. For atmospheric vortices, mixed wave/vortex dynamics has been extended to explain the propagation of spiral rainbands and the development of dynamical instability in tropical cyclones. Finally, we review wave and basic flow interaction in torrential rainfall, for which it was necessary to extend existing theory from large-scale flows to mesoscale fields, enriching our knowledge of mesoscale atmospheric dynamics. 相似文献
7.
针对2001年4月上旬一次蒙古气旋发展过程中的地形因素进行了观测和模拟研究, 结果表明:依据低层冷空气是否越过阿尔泰—萨彦岭山地产生气旋冷锋, 蒙古气旋的发生发展过程可以划分为触发和发展两个阶段。在气旋的发展阶段, 斜压不稳定是其主要强迫机制。伴随地形对低层冷空气阻滞程度的变化, 蒙古气旋经历了从缓慢发展到剧烈加强的过程。阿尔泰—萨彦岭山地通过对低层冷空气的阻滞使山地上空等熵面更为陡立, 加强了对流层低层的斜压强迫, 从而使斜压强迫的涡度增长向低层聚集, 导致气旋发展强度增强。阿尔泰—萨彦岭山地及其南侧形成的峡谷地形对低空急流的位置、范围、强度及演变过程具有较重要影响。另外, 对流层高层位涡平流也是气旋发展的一个强迫因素, 但其影响较小。 相似文献
8.
等熵面和湿等熵面倾斜发展的诊断分析 总被引：3，自引：0，他引：3
利用等压坐标系中的热力学方程和水汽方程推导出可以诊断分析等熵面（等位温面）和湿等熵面（等相当位温面） 倾斜变化的倾角方程。等熵面倾角的局地变化由倾角平流输送项、风速切变项和非绝热加热项共同决定，而影响湿等熵面倾角局地变化的强迫项除倾角平流输送项、风速切变项和非绝热加热项之外，还包括垂直热量通量切变项。NCEP/NCAR实时分析资料的分析结果表明，大气斜压性、相对垂直涡度与等熵面和湿等熵面的倾角密切相关，它们的正高值区互相重叠；垂直风速切变项，特别是垂直速度的经向切变项是影响等熵面倾斜发展的主要强迫项，而纬向和经向风速的垂直切变项对湿等熵面倾角演变的贡献最大。 相似文献
9.
利用欧洲中期天气预报中心（ECMWF）提供的0.5°×0.5° ERA-Interim再分析资料，麦迪逊-威斯康星大学气象卫星研究所（CIMSS）提供的地球静止环境业务卫星（GOES-EAST）红外卫星云图和天气预报模式（WRF）的模拟结果，对2018年1月3—6日发生在北大西洋上的一个具有“T”型（T-bone）锋面结构的超强爆发性气旋进行分析。该爆发性气旋在较暖的湾流上空生成，沿海表面温度大值区向东北方向快速移动，生成后6 h内爆发性发展，24 h中心气压降低48.7 hPa。高空槽加深、涡度平流加强和低层较强的大气斜压性为气旋快速发展提供了有利的环流背景场。由于气旋发展迅速，低层相对涡度急剧增大，低压中心南部来自西北方向的干冷空气随气旋式环流快速向东推进，与东南暖湿气流汇合，锋生作用较强。较暖的洋面对西北冷空气的加热作用使得交汇的冷、暖空气温度梯度较小。减弱东移的冷锋与暖锋逐渐形成近似垂直的“T”型结构。用Zwack-Okossi方程诊断分析表明，非绝热加热、温度平流和正涡度平流是该爆发性气旋发展的主要影响因子。气旋初始爆发阶段，西北冷空气进入温暖的洋面，海洋对上层大气感热输送和潜热释放较强，非绝热加热对气旋快速发展有较大贡献。气旋进一步发展，“T”型锋面结构显著，温度平流净贡献较大，对气旋的发展和维持起重要作用。 相似文献
10.
11.
WANG Jianjie 《Acta Meteorologica Sinica》2000,14(2):173-192
In this study,the predictability and physical processes leading to the rapid frontal cyclogenesis,that took place in the east coast of the U.S.during 3-4 October 1987,are examined using a nestedgrid.mesoscale model with a fine-mesh grid size of 25km.It is shown that the model reproduces reasonably well the cyclogenesis in a coastal baroclinic zone.its subsequent deepening and movement as well as the pertinent precipitation.It is found that the frontal cyclogenesis occurs in a favorable large-scale environment with pronounced thermal advection in the lower troposphere and marked potential vorticity(PV) concentration aloft associated with the tropopause depression.The transport of warm and moist air from the marine boundary layer by the low-level in-shore flow provides the necessary energy source for the observed heavy precipitation and a variety of weather phenomena reported in the cold sector.Several 24-h sensitivity simulations are performed to examine the relative importance of diabatic heating,adiabatic dynamics and various initial conditions in the frontal cyclogenesis.It is found that latent heat release,even though quite intense,accounts for only 25% of the cyclone's total deepening in this case:the weak impact seems due to the occurrence of latent heating in the cold sector and the upward lifting of the dynamical tropopause by diabatic updrafts.Vorticity budgets show that the lowlevel thermal advection dominates the incipient stage,whereas the vorticity advection determines the rapid deepening rate at the mature stage.The results reveal that the predictability of the present storm is closely related to the vertical coupling between the surface cyclone and the upper-level PV core,which is in turn determined by initial offshore perturbations in the lower troposphere. 相似文献
12.
一次华南持续性暴雨的动力诊断分析和数值模拟 总被引：2，自引：2，他引：0
利用倾斜涡度发展（slantwise vorticity development,SVD）理论,对2008年6月中旬华南地区持续性暴雨进行了动力学机制的诊断分析,讨论了低空急流（10wleveljet,Lu）在低涡发展过程中起的作用,同时利用MM5数值模式对暴雨过程进行了验证并对模拟结果进行了进一步分析。结果表明,高原低涡的发展是前期广西地区降水的主要动力因素,由于湿等熵面相对地形倾斜,且气块沿等熵面有相对运动,同时满足热力学参数CM〈0的条件,使得SVD发生作用,导致低涡移出高原后得到进一步发展;而LLJ的增强改变了大气斜压性,是后期低涡继续东移发展,并造成广东地区持续性暴雨的重要原因。数值模拟控制试验结果很好地反映了这次低涡降水的发展过程。敏感性试验结果初步表明,LLJ改变了低层大气稳定度和风的垂直切变,即大气斜压性增强,从而促进了中尺度低涡的进一步发展。 相似文献
13.
Dynamical and Thermal Problems in Vortex Development
and Movement. Part II: Generalized Slantwise
Vorticity Development 
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下载免费PDF全文 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. 相似文献
14.
Hou Dingchen 《Acta Meteorologica Sinica》1991,5(1):40-50
Based on the theory of Ertel potential vorticity,the isentropic potential vorticity maps and vertical profiles of potential vorticity for two summer cyclones over the Changjiang-Huaihe Valley are analysed.After discussing a possible mechanism for the genesis and development of such systems and their differences from typical extratropical cyclones,a conceptual model for their activities is proposed:A weak disturbance in the midlevel of troposphere originated from around the Qinghai-Xizang Plateau may cause heavy precipitation under favourable conditions and latent heat release in the mid-troposphere leads to downward extension of cyclonic circulation and a wave on the quasi-stationary front.This weak cyclone can develop substantially and become a typical extratropical cyclone only when air from the lower stratosphere flows downslope along isentropic surfaces into the region of interest. 相似文献
15.
Dr. J. Manobianco L. W. Uccellini K. F. Brill P. J. Kocin 《Meteorology and Atmospheric Physics》1991,45(1-2):41-63
Summary The nudging assimilation scheme described in the companion paper by Brill et al. is applied to study oceanic cyclogenesis during GALEIOP 10 on 27–28 February 1986. A 36-h control simulation statically initialized from 0000 UTC 27 February 1986 data moves the cyclone too far north and east in the 12-h period of most rapid deepening limiting the usefulness of the simulation for diagnostic study. The use of nudging to dynamically assimilate special 3-h and routine 12-h rawindsonde and dropsonde data into the model during the entire 36-h forecast period failed to deepen the cyclone as it moved northeast off the Atlantic seaboard beyond the area covered 3-h by sounding data. Subjectively analyzed mean sea-level pressures (MSLP) were included in the data base to allow the model to nudge toward 3-h surface pressure analyses extended to cover the region of cyclogenesis over the ocean. The assimilation of 3-h surface data over the ocean is insufficient to produce a realistic simulation of cyclogenesis. This result motivated the use of the nudging technique to assimilate surface pressure and upper air data over land during the 12-h pre-cyclogenetic period (i.e. dynamic initialization) and compare the subsequent 24-h simulation with one initialized statically at the same synoptic time.Dynamic initialization produced the best simulation of the occanic cyclone based upon the standard statistical scores and positions of the MSLP minima. This simulation is used to diagnose differences between cyclogenesis during GALEIOP 1 and IOP 10. Isentropic analyses and vertical cross sections are derived from the model simulations and are used to contrast the strength of the upper tropospheric forcing and the low-level static stability associated with each case. The results of the diagnostic analyses reveal that stronger surface response (based upon MSLP minima) to weaker upper-level forcing during GALEIOP 10 (compared with GALEIOP 1) was associated with differences in the lower tropospheric static stability and thermal advection patterns and their interaction with upper tropospheric features.With 19 Figures 相似文献
16.
利用高分辨率观测资料和ERA5再分析资料, 分析造成2021年11月7—8日东北极端暴雪的温带气旋结构特征及爆发性发展机制, 结果表明:温带气旋发生在高空冷涡背景下, 地面气旋在黄海形成后出现爆发性快速增强并沿东北地区东部北上。地面降雪区主要分布在气旋西侧, 且降雪强度与气旋的发生发展密切相关;地面气旋在爆发性发展后由叶状云系演变为逗点涡旋云系, 并表现出明显的锋面断裂和暖锋包卷;其垂直结构也先后出现高空锋区断裂、干暖核形成和中性锢囚锋区加强;西伯利亚高压脊、华北高空槽和东北高压脊3个异常中心构成Rossby波列, 随着高度异常中心不断东移及波能量向下游地区频散, 华北高空槽区的波作用通量明显增大导致华北冷涡快速增强, 涡度因子的急剧增大有利于地面气旋爆发性发展;随着平流层位涡高值区沿等熵面不断向南发展和向下传播, 导致中层冷涡快速发展并向下伸展, 诱发地面气旋爆发性增强。 相似文献
17.
Abstract In this study, the development of a moderate coastal storm with intense precipitation that occurred during 12–14 February 1993 is examined using a high‐resolution version of the Canadian Regional Finite‐element (RFE) model with more realistic physical representations. It is shown that the improved RFE model predicts well the coastal cyclogenesis events and also the distribution and intensity of heavy mixed precipitation (rain and snow) associated with the storm. It is found that the cyclogenesis takes place in response to the low‐level inshore advection of high‐θe air from the maritime boundary layer, and the approach of a mid‐level shortwave trough with a warm pool above that is previously associated with a decaying cyclone upstream. More rapid deepening of the cyclone ensues as intense precipitation falls along the warm and cold fronts near the cyclone centre. Diagnosis of the control and sensitivity simulations reveals that the low‐level inshore warm advection and the propagation of the stratospheric warm pool contribute more significantly to the surface pressure falls during the incipient stage, whereas the mid‐level shortwave trough plays an important role in the cyclogenesis at later stages. Overall, latent heat release accounts for about 50% of the cyclone's total deepening, in agreement with the presence of a moderate baroclinic environment and the generation of intense precipitation. The diabatic and kinematic structures near the rain‐snow boundary are examined to gain insight into the influence of melting snow on the cyclogenesis. It is shown that the improved RFE model reproduces well the rain‐snow boundary structures as previously observed. Moreover, a thermally indirect circulation (perturbation) can be seen in the vicinity of the rain‐snow boundary. It is found, however, that melting of snow tends to produce a weak negative or negligible impact on the cyclogenesis, as opposed to previous hypotheses. 相似文献
18.
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. 相似文献
19.
利用常规地面气象观测资料、NCEP/NCAR FNL 1°×1°网格点逐6 h再分析资料,对2018年6月20日浙江省一次暴雨过程的主要环流系统、等熵位涡、垂直螺旋度等进行了天气动力学诊断分析。结果表明：850 hPa低涡切变、对流层中层冷空气、200 hPa南亚高压、副热带高压是此次暴雨过程发生的主要影响系统;700 hPa上的正垂直螺旋度中心对暴雨的发生有良好的指示意义;等熵位涡的演变和形态对冷空气活动有较好的视踪作用,等熵位涡中心两侧气流辐合,有利于低压系统发展,高层等熵位涡与冷空气活动有较好的对应关系,等熵位涡大值区偏南侧的移动与强降水落区有较好的对应关系。 相似文献
20.
The development mechanisms of the explosive cyclone that occurred during 3–4 April 2012 over East Sea (Sea of Japan) are examined through numerical simulation and sensitivity experiments using the Weather and Research Forecasting (WRF) model. The characteristics of this explosive cyclone are different from typical cyclonic features observed in this region, including its intensity, deepening rate, and formation time. Numerical simulation, reanalysis data, upper and surface weather charts, and satellite data indicate that the strong baroclinic instability and temperature advection associated with upper-level cut-off low and the interaction of potential vorticity (PV) anomalies between the lower- and upper-level are essential to explosive cyclogenesis.The sensitivity experiments of the explosive cyclone show that latent heat release (LHR) is an important factor in explosive cyclogenesis. The intensification, extent, and movement speed of the cyclone are amplified by LHR as well as the formation of an upper-level cut-off low. The role of LHR is primary important in the generation and evolution of the cyclone. Especially, the LHR contributes to roughly 50% of decrease in sea level pressure (SLP) and 50% of the central cyclone’s low-level PV generation in initial stage. During a 48-h simulation, the contributions of the LHR, surface heat flux, and their interaction on the decrease of SLP of the cyclone are found to be 40.6, −8.2, and 10.5%, respectively. These results reveal that the explosive cyclone has larger deepening rates than OJ cyclones, and develops with a large amount of LHR near the cyclone center. 相似文献