共查询到19条相似文献，搜索用时 155 毫秒
1.
Previous studies showed that 4 D-Var technique used for data assimilation could be modified for weather control. This study demonstrates the ability of 4 D-Var to influence the future path of a tropical cyclone by calculating perturbations in WRF simulation. Given the background error covariance matrix, the initial field is improved by the vortex dynamic initialization technique. Our results show that 4 D-Var can be applied to control the trajectory of simulated tropical cyclones by producing "optimal" perturbations. In the numerical simulation experiment of Typhoon Mitag in 2019, after this kind of weather control similar to data assimilation, the tropical cyclone moved obviously,and the damaging wind over the coastline weakened. The prediction results after the initial field modified by 4 D-Var have a great change, and the position of the tropical cyclone moved about 0.5° southeastward after assimilation,which misses the southeast coast of China. Moreover, the damaging wind is also weakened. Since the 4 D-Var is premised on the assumption that the model is perfect and does not consider the model error, then the research plan to consider model error and introduce new methods is discussed in the paper. 相似文献
2.
The aim of this study is to examine the difference in tropical cyclone(TC) formation in different cyclonic circulation locations using a mesoscale model on a beta plane. A weak initial vortex is imposed at different positions in a cyclonic circulation. Numerical experiments indicate that the tropical disturbances located in the center and northeastern parts of the cyclonic circulation are favorable to TC formation, while those located in the south of the cyclonic circulation are unfavorable. Since the asymmetric circulation induced by the beta effect peaks in the northeastern quadrant of the vortex, when the initial vortex is placed in the southern part of the cyclonic circulation, the vortex begins to develop in the south due to the effect of the westerly wind of the cyclonic circulation. The westerly wind of the cyclonic circulation gradually decreases and the vortex is contributed mainly by the beta effect afterwards. Thus, establishment of the convection–circulation–moisture positive feedback is delayed, unfavorable to TC rapid development. On the contrary, when the initial vortex is placed in the northern part of the cyclonic circulation, the superposition of the beta gyres and easterly wind of the cyclonic circulation induces stronger wavenumber-1 wind in the northeastern part of the vortex. The greater asymmetric wind is closely associated with the symmetric wind through energy conversion, thus accelerating a positive feedback and facilitating vortex development into a stronger TC. Meanwhile, when the initial vortex is placed in the center and eastern parts of the cyclonic circulation, the vortex develops a little slower than when it is placed in the northern part, but stronger than when placed in the southern part. 相似文献
3.
The formation of a tropical cyclone is the result of a process in which an initial disturbance evolves into a warm-core low-pressure system; however, the origin of the initial disturbance and the features of the initial fields are overlooked in most existing theories. In this study, based on FY-2C brightness temperature data and the Japan reanalysis dataset, the origin and evolution of the tropical disturbance that became Typhoon Fung-Wong (2008) were examined. The results demonstrated that the initial disturbance emerged within a saddle-type field with large vertical tropospheric wind shear. The vertical wind shear decreased with the adjustment of the upper circulation; moreover, accompanied by convection over the warm section around the upper cold vortex, it provided favorable thermal and dynamic conditions for the development of a tropical vortex. During its development, the zone of associated positive relative vorticity strengthened and descended from the mid-troposphere to lower levels. This rapid strengthening of lower-level vorticity was due to increasing convergence related to the intensification of the pressure gradient southwest of the subtropical high. This indicated that the upper cold vortex and West Pacific subtropical high played very important roles in this case. 相似文献
4.
钟元 《热带气象学报(英文版)》1997,3(2):208-214
As shown in a statistical analysis of the relationship between environmental fields at varied timeand tropical cyclone motion, the forecasting ability of the initisl environmental field predictors for tropical cyclone motion decreases with the increase of valid time period of forecast;it is higher with these predictors at a fUture time than at an initial time. The work also indicates that for the tropical cyclone motion over a given period of valid forecast, better predictors appear at times mostly differing from thevalid periods; for periods at 48-120 h the environmental predictors at 48-72 h are more capable of forecasting. With statistical interpretation of NWP products, a predictive model for tropical cyclone motionis superior in performance over a statistical forecasting model that employes predictors of the initial field in the basic framework. The concluding remarks can be used as reference in the construction of an objective prediction model for tropical cyclone motion. 相似文献
5.
Luo Zhexian 《Acta Meteorologica Sinica》1994,8(1):51-59
The energy dispersion of a typhoon vortex and its effect on the typhoon motion are studied using an analytical method of double-Fourier expansion as well as a numerical model in a β-plane nondivergent barotropic framework.The analytic model and the linear version of the numerical model give essentially the same result:the energy dispersion from a tropical cyclone can creat an L-H-L wave train to the east of the tropical cyclone.Three numerical experiments,integrated for 7 model days by the nonlinear model,indicate that the closed high in the wave train produces obvious influence on the structure and movement of the tropical cyclone. 相似文献
6.
A Relocation-based Initialization Scheme to Improve Track-forecasting of Tropical Cyclones简 总被引：2，自引：0，他引：2
A relocation procedure to initialize tropical cyclones was developed to improve the representation of the initial conditions and the track forecast for Panasonic Weather Solutions Tropical Operational Forecasts. This scheme separates the vortex perturbation and environment field from the first guess, then relocates the initial vortex perturbations to Lhe observed position by merging them with the environment field. The relationships of wind vector components with stream function and velocity potential are used for separating the vortex disturbance from first guess. For the separation of scalars, a low-pass Barnes filter is employed. The irregular-shaped relocation area corresponding to the specific initial conditions is determined by mapping the edge of the vortex radius in 36 directions.Then, the non-vortex perturbations in the relocation area are removed by a two-pass Barnes filter to retain the vortex perturbations, while the variable fields outside the perimeter of the modified vortex are kept ide.ntical to the original first guess. The potential impacts of this scheme on track forecasts were examined for three hurricane cases in the 2011-12 hurricane season. The experimental results demonstrate that the initialization scheme is able to effectively separate the vortex field from the environment field and maintain a relatively balanced and accurate relocated first guess. As the initial track error is reduced, the following track forecasts are considerably improved. The 72-h average track forecast error was redu,~ed by 32.6% for the cold-start cases, and by 38.4% when using the full-cycling data assimilation because of the accumulatedL improvements from the initialization scheme. 相似文献
7.
A relatively independent and small-scale heavy rainfall event occurred to the south of a slow eastward-moving meso-α-scale vortex. The analysis shows that a meso-β-scale system is heavily responsible for the intense precipitation. An attempt to simulate it met with some failures. In view of its small scale, short lifetime and relatively sparse observations at the initial time, an adjoint model was used to examine the sensitivity of the meso-β-scale vortex simulation with respect to initial conditions. The adjoint sensitivity indicates how small perturbations of initial model variables anywhere in the model domain can influence the central vorticity of the vortex. The largest sensitivity for both the wind and temperature perturbation is located below 700 hPa, especially at the low level. The largest sensitivity for the water vapor perturbation is located below 500 hPa, especially at the middle and low levels. The horizontal adjoint sensitivity for all variables is mainly located toward the upper reaches of the Yangtze River with respect to the simulated meso-β-scale system in Hunan and Jiangxi provinces with strong locality. The sensitivity shows that warm cyclonic perturbations in the upper reaches can have a great effect on the development of the meso-β-scale vortex. Based on adjoint sensitivity, forward sensitivity experiments were conducted to identify factors influencing the development of the meso-β-scale vortex and to explore ways of improving the prediction. A realistic prediction was achieved by using adjoint sensitivity to modify the initial conditions and implanting a warm cyclone at the initial time in the upper reaches of the river with respect to the meso-β-scale vortex,as is commonly done in tropical cyclone prediction. 相似文献
8.
Adjoint Sensitivity Experiments of a Meso-β-scale Vortex in the Middle Reaches of the Yangtze River 总被引：1，自引：0，他引：1
A relatively independent and small-scale heavy rainfall event occurred to the south of a slow eastwardmoving meso-α-scale vortex. The analysis shows that a meso-β-scale system is heavily responsible for the intense precipitation. An attempt to simulate it met with some failures. In view of its small scale, short lifetime and relatively sparse observations at the initial time, an adjoint model was used to examine the sensitivity of the meso-β-scale vortex simulation with respect to initial conditions. The adjoint sensitivity indicates how small perturbations of initial model variables anywhere in the model domain can influence the central vorticity of the vortex. The largest sensitivity for both the wind and temperature perturbation is located below 700 hPa, especially at the low level. The largest sensitivity for the water vapor perturbation is located below 500 hPa, especially at the middle and low levels. The horizontal adjoint sensitivity for all variables is mainly located toward the upper reaches of the Yangtze River with respect to the simulated meso-β-scale system in Hunan and Jiangxi provinces with strong locality. The sensitivity shows that warm cyclonic perturbations in the upper reaches can have a great effect on the development of the meso-β-scale vortex. Based on adjoint sensitivity, forward sensitivity experiments were conducted to identify factors influencing the development of the meso-β-scale vortex and to explore ways of improving the prediction. A realistic prediction was achieved by using adjoint sensitivity to modify the initial conditions and implanting a warm cyclone at the initial time in the upper reaches of the river with respect to the meso-β-scale vortex, as is commonly done in tropical cyclone prediction. 相似文献
9.
THE STRUCTURE OF TROPICAL CYCLONE BY TOVS AND ITS APPLICATION IN NUMERICAL WEATHER PREDICTION 总被引：1，自引：2，他引：1
The TOVS data are used to study the structure of a number of tropical cyclones for the year 2000.
Differences are found to some extent between what is found and classic conceptual models in that (1) the
horizontal structure is asymmetric and variable so that the low-value centers at low levels of the geopotential
height field (or the high-value centers at high levels) do not necessarily coincide with the high-value centers of
the temperature field; (2) the vertical structure is also variable in the allocation of the anomalies of the
geopotential height field between low values at low levels and high values at high levels. It is especially noted
that the centers of the anomalies are tilting at both high and low levels or the high level is only at the edge of a high-pressure zone. There is not any significant high-value anomalous center in a corresponding location with the
tropical cyclone. The structure of tropical cyclone in the TOVS is also used as reference to modify the structure of typhoon BOGUS in the numerical prediction model system of tropical cyclones. It is found that the modified BOGUS
performs better in coordinating with the environment and predicting the track of the tropical cyclone. The
demonstration is two-fold — the structure of the typhoon BOGUS is such that it means much in the track
prediction and the use of the TOVS-based tropical cyclone structure really helps in improving it. It provides the
foundation for modification and evolution of typhoon BOGUS. 相似文献
10.
李小凡 《热带气象学报(英文版)》1996,2(2):148-154
Development of a tropical cyclone in barotropic environmental flows is investigated with a shallow water model. It is found that the tropical cyclone develops only when it is embedded in an environmental now with a southward relative vorticity gradient. The related physical mechanism is explained by analyzing the kinetic energy conversion between the environmental flow and tropical cyclone circulation. 相似文献
11.
国家气象中心台风路径数值预报模式自1996年6月投入业务运行以来, 一直在背景场中采用经验平滑滤波技术消除浅台风和嵌入轴对称的台风bogus涡旋技术。但事实上, 在采用经验平滑技术消除背景场中弱的位置不准确的浅台风涡旋同时, 也滤除了台风中心周围一些宝贵的非对称气流结构, 同时, 由于实际的台风涡旋结构是非对称的, 因而对采用轴对称涡旋的模式初始场而言, 或多或少的贡献了一些模式预报结果的路径误差。为了调查这部分非对称结构对台风预报路径误差的影响, 从T213L31全球谱模式提供的背景场中抽取浅台风周围的非对称流场, 将之加入到轴对称的台风bogus涡旋中。初步的个例试验发现, 加入非对称流场后, 能有效地减少台风路径预报误差。 相似文献
12.
全球数值模式中的台风初始化Ⅰ:方案设计 总被引：2，自引：0，他引：2
由于缺少大量有效的观测资料,台风初始化对数值天气预报业务模式而言,仍然是一个悬而末决的难题.中国国家气象中心自从1996年将台风数值预报系统投入业务运行以来,一直使用经验的人造bogus涡旋台风初始化技术.实际上,不同时期的台风有着不同的环流结构,即使同一个台风在不同的生命期也具有不同的结构特征,而这些结构特征的差异并不能依靠现有的bogus涡旋技术体现出来,这种主观方法的统一性与台风在时空上的差异性形成了强烈的反差.最近,基于国家气象中心全球资料分析同化-预报循环系统,设计和发展了一套新的台风初始化业务方案,它主要由初始涡旋形成、涡旋重定位和涡旋调整3部分过程组成.相比于业务中使用的人造bogus涡旋台风初始化方案,新方案在很大程度上减少了人为因素对台风涡旋结构的影响,而更多地是依靠数值模式自身的动力和物理过程来协调约束产生三维空间的涡旋结构.应用新方案,文中对生成于西北太平洋的2006年0605号台风格美(Kaemi)进行了数值试验,初步分析表明,新方案在实现台风涡旋环流结构的初始化方面效果较好,同时,对台风格美多个时次的预报结果也显示,相比于业务使用的bogus方案而言,新方案对台风路径平均预报误差有了大幅度的降低. 相似文献
13.
利用ERA-Interim逐日再分析资料及中国753站逐日降水资料,对2008年3月23—28日的东北冷涡天气过程进行诊断分析,并探讨了冷涡降水的主要影响因子。结果表明：1）与夏季冷涡过程不同,此次初春冷涡过程高层环流场由经向环流向纬向环流转变;冷涡发展初期,经向环流的建立使得冷涡向南移动,而成熟阶段冷涡后部的低槽引导冷空气向冷涡输送,导致了冷涡环流的维持。2）亚欧大陆上空强阻塞形势的发展是初春东北冷涡形成的关键因子;乌拉尔山和鄂霍次克海阻塞高压分别受到前期北大西洋和热带太平洋海温异常的调控,为冷涡向南发展维持提供了有利的环流背景,并影响了高低空急流的配置,有利于冷涡降水的形成。3）涡度场和温度场的高低空配置使得东北冷涡发展成深厚的环流系统,干侵入对冷涡的形成和维持同样有重要作用。冷涡环流的发展为东北地区降水提供了有利的水汽和垂直运动条件,冷暖平流交汇引起的锋面过程则促进大范围降水的形成。 相似文献
14.
Previous studies concerning the interaction of dual vortices have been made generally in the deterministic framework. In this paper, by using an advection equation model, eight numerical experiments whose integration times are 30 h are performed in order to analyze the interaction of dual vortices and the vortex self-organization in a coexisting system of deterministic and stochastic components. The stochastic components are introduced into the model by the way that the Iwayama scheme is used to produce the randomly distributed small-scale vortices which are then added into the initial field. The different intensity of the small-scale vortices is described by parameter K being 0.0, 0.4, 0.6, 0.8, and 1.0, respectively. When there is no small-scale vortex （K=0.0）, two initially separated meso-beta vortices rotate counterclockwise mutually, and their quasi-final flow pattern is still two separated vortices; after initially incorporating small-scale vortices （K=0.8, 1.0）, the two separated meso-beta vortices of initially same intensity gradually evolve into a major and a secondary vortex in time integration. The major vortex pulls the secondary one, which gradually evolves into the spiral band of the major vortex. The quasi-final flow pattern is a self-organized vortex with typhoon-like circulation, and the relative vorticity at its center increases with increasing in K value, suggesting that small-scale vortices feed the self-organized vortex with vorticity. This may be a possible mechanism responsible for changes in the strength of the self-organized vortex. Results also show that the quasi-final pattern not only relates with the initial intensity of the small-scale vortices, but also with their initial distribution. In addition, three experiments are also performed in the case of various boundary conditions. Firstly, the periodic condition is used on the E-W boundary, but the fixed condition on the S-N boundary; secondly, the fixed condition is set on all the boundaries; and thirdly, the periodic conditio 相似文献
15.
以往双涡相互作用的动力学一般都在决定性的框架内研究。文中用一个平流方程模式,实施积分时间为30 h的8组试验,分析决定性和随机性共存系统中双涡相互作用和涡旋自组织的问题。随机性通过以下方式引入模式:先用Iwayama方案生成随机分布的小尺度涡,再将这些小尺度涡加入初始场。试验中,初始随机分布小尺度涡的强度参数K分别取0.0、0.4、0.6、0.8和1.0。结果表明,没有小尺度涡的条件下(K=0.0),初始分离的两个β中尺度涡逆时针互旋,其准终态流型是两个分离的涡;引进小尺度涡后,K取0.8、1.0时,初始分离强度相同的两个β中尺度涡,逐渐形成主次之分。主涡将次涡拉伸成为螺旋带,其准终态流型是一个自组织起来的类似于台风环流的涡旋。准终态涡中心的相对涡度值随K值的加大而加大。结果还表明,准终态流型不仅与初始小尺度涡的强度参数有关,而且与初始小尺度涡的分布有关。此外,在相同初始场的情况下,还实施了3类不同边畀条件的试验:第1类,在东西边界取周期条件,在南北边界取固定条件;第2类,在所有边界均取固定条件;第3类,在所有边界均取周期条件。这3类试验的准终态流型相同,都显示出一个类似于台风涡旋的环流。根据这些结果可以初步认为,涡旋自组织的研究从决定性动力学向随机动力学的过渡是值得探索的。 相似文献
16.
An Investigation into Effect of Randomly Distributed Small Scale Vortices on Vortex Self-Organization 
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下载免费PDF全文 Previous studies concerning the interaction of dual vortices have been made generally in the determin-istic framework. In this paper, by using an advection equation model, eight numerical experiments whose integration times are 30 h are performed in order to analyze the interaction of dual vortices and the vortex self-organization in a coexisting system of deterministic and stochastic components. The stochastic compo-nents are introduced into the model by the way that the Iwayama scheme is used to produce the randomly distributed small-scale vortices which are then added into the initial field. The different intensity of the small-scale vortices is described by parameter K being 0.0, 0.4, 0.6, 0.8, and 1.0, respectively. When there is no small-scale vortex (K=0.0), two initially separated meso-beta vortices rotate counterclockwise mutu-ally, and their quasi-final flow pattern is still two separated vortices; after initially incorporating small-scale vortices (K=0.8, 1.0), the two separated meso-beta vortices of initially same intensity gradually evolve into a major and a secondary vortex in time integration. The major vortex pulls the secondary one, which gradually evolves into the spiral band of the major vortex. The quasi-final flow pattern is a self-organized vortex with typhoon-like circulation, and the relative vorticity at its center increases with increasing in K value, suggesting that small-scale vortices feed the self-organized vortex with vorticity. This may be a pos-sible mechanism responsible for changes in the strength of the self-organized vortex. Results also show that the quasi-final pattern not only relates with the initial intensity of the small-scale vortices, but also with their initial distribution. In addition, three experiments are also performed in the case of various boundary conditions. Firstly, the periodic condition is used on the E-W boundary, but the fixed condition on the S-N boundary; secondly, the fixed condition is set on all the boundaries; and thirdly, the periodic condition is chosen on all the boundaries. Their quasi-final flow patterns in the three experiments are the same with each other, exhibiting a larger scale typhoon-like circulation. Based on these results mentioned above, authors think that the transition of vortex self-organization study from the deterministic system to the coexisting system of deterministic and stochastic components is worth exploring. 相似文献
17.
2006年7—9月西北太平洋热带气旋季节活动的数值模拟 总被引：4，自引：1，他引：3
利用NCEP（National Centers for Environmental Prediction）提供的1°×1°的FNL（final）资料和中尺度WRF（Weather Research and Forecasting）模式,研究了热带气旋（tropical cyclone,简记TC）动力季节预报的可能性,通过在27km的粗网格中运用张弛逼近（Nudging）技术,对2006年7-9月西北太平洋TC活动进行了92d的连续数值积分。与观测结果比较表明,WRF模式不仅较好地模拟了MJO（Madden-Julian oscillation）和准双周振荡的活动情况,而且模拟的TC频数、移动路径和强度都与实际观测结果比较接近。在嵌套的9km网格中,不仅模拟出眼墙、暖心等TC结构的主要特征和TC的西行盛行路径及登陆活动情况,而且所模拟的生成过程包括早期研究中提出的TC生成过程中的两次快速发展的过程。模拟的TC初始涡旋主要出现在季风槽中,伴随准双周振荡活动,它的第一次发展在初始涡旋中心形成强烈的对流区;经过一段时间的减弱后,在有利的大尺度形势下,涡旋中心湿水汽层迅速增厚,导致气旋的第二次强烈发展。 相似文献
18.
1INTRODUCTIONEversincethe1940抯,thetropicalcyclone(TC)hasbeenviewedasapointvortexorrigidvortex.Thepredictionissummedupasoneforairflowintheambientfield.Themethodusuallysucceeds.Thesteeringtheoryfortheairflowbecomesitstheoreticalfoundation.Thoughwithsomesuccess,theactualtrackofTCmovementcanbemuchdeviatedfromthesteeringcurrent,asseeninroutineforecastpractice.Withoutmuchchangesintheambientsteeringcurrent,theTCcanhaveunexpectedchangesinthedirection,speedofmotionorintensity.Atypicalexamplewo… 相似文献
19.
空间加密探空观测资料对西南低涡暴雨天气过程数值模拟的影响 总被引：1，自引：0，他引：1
本文基于AREM（Advanced Regional Eta Model）模式,结合中国气象局成都高原气象研究所西南低涡加密观测科学试验得到的探空观测第一手资料,通过对2012年7月3～4日四川区域性暴雨天气过程（20120703过程）进行数值模拟分析,结果表明:（1）降水雨带的分布主要取决于西南低涡移动路径,不同初值会使得低涡路径在磨合协调期产生强摆动,稳定后则在此基础上,随着环境流场继续移动发展。（2）引入4个加密探空站点资料会对整个大气物理量场造成一定影响,最大差值分布在这些站点附近,热力和动力物理量场最大偏差中心并不重合。时间演变直观地说明了初值对局地大气状态的影响时段有限,主要集中在前期,与模式自身调整期相重叠。（3）初始的大气状态必然会随着模式的磨合过程进行调整,不同初值在调整期能对中小尺度低涡系统的位置及强度产生影响,形成各自稳定的低涡系统初态。（4）低涡中心所对应的散度、涡度、垂直速度关系非常密切,但三者强度和发展高度的演变并非完全一致。 相似文献