| 非对称台风bogus方案设计和初步试验 |
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| 引用本文： | 瞿安祥,麻素红.非对称台风bogus方案设计和初步试验[J].应用气象学报,2007,18(3):380-387. |
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| 作者姓名： | 瞿安祥 麻素红 |
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| 作者单位： | 国家气象中心, 北京 100081 |
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| 摘 要： | 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。
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| 关 键 词： | 台风bogus涡旋 轴对称结构 非对称结构 |
| 收稿时间： | 2006-03-03 |
| 修稿时间： | 2006-03-032006-11-07 |
The Design of Asymmetric Bogus Vortex Scheme and Preliminary Experiment |
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| Qu Anxiang,Ma Suhong.The Design of Asymmetric Bogus Vortex Scheme and Preliminary Experiment[J].Quarterly Journal of Applied Meteorology,2007,18(3):380-387. |
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| Authors: | Qu Anxiang Ma Suhong |
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| Affiliation: | National Meteorological Center, Beijing 100081 |
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| Abstract: | The Model for Typhoon Track Prediction(MTTP) at National Meteorological Center(NMC), which has provided operational guidance for forecasters since June 1996,has always been imposed a scale-selective sophisticated filtering to remove the incorrect shallow vortex from the first guess fields and has implemented axisymmetric bogus vortex into the initial condition.However,with the upgrade of global spectral model system at NMC(from T106 to T213),the global forecast model now has a horizontal resolution that allows the representation of the tropical cyclone (TC) circulation,although the resolution is not adequate for resolving the inner core structure.Correspondingly,some valuable information about TC physical characteristics can be provided by the first guess fields from global gridded analyses.When damping out the entire shallow vortex of first guess fields,the background circulation around TC center has already been smoothed away by sophisticated filtering scheme,especially the asymmetric wind components,and it has adverse effect on the modified background field.Nowadays,the operational TC initialization scheme is constructed from a bogus vortex based on a few parameters analyzed by forecasters(such as TC central pressure,central position and radius of 15 m/s wind) and has an axisymmetric property.Because TC vortex has an obvious character of asymmetric structure,the implementation of axisymmetric property can contribute to partial track forecast biases more or less.In order to investigate the impact of background asymmetric circulation on the TC track forecast, an experimental scheme to introduce asymmetry into TC bogus vortex is carried out as follows: Extract asymmetric component of geopotential height from first guess fields by taking the difference between the total geopotential height and its azimuthal average about TC center;derive gradient wind from an azimuthal average of the total geopotential height;extract asymmetric component of wind by taking the difference between gradient wind and total wind of first guess fields;merge asymmetric components into axisymmetric bogus vortex and produce TC initial condition of MTTP model.It is expected that the scheme can provide a significant enhancement of initial TC asymmetric circulation and structure.Using the new scheme,a total of 12 forecast experiments for typhoon Sinlaku in 2002 are performed and the track forecast skills are evaluated in comparison with the operational ones.From the study it is found that much more accurate TC bogus data are produced by the new scheme compared with operational one.The verification of the experiments also shows that mean track forecast biases can be reduced effectively by introducing asymmetric components into axisymmetric bogus vortex. |
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| Keywords: | TC bogus vortex axisymmetric structure asymmetric structure |
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