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气象:2016,42(6):664-673
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T639全球模式的台风初始化方案升级试验
(国家气象中心,北京 100081)
Updated Experiments of Tropical Cyclone Initialization in Global Model T639
(National Meteorological Centre, Beijing 100081)
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投稿时间:2014-12-21    修订日期:2016-02-04
中文摘要: 由于洋面上缺少有效的台风观测资料,台风初始化对全球数值预报业务模式而言,仍然是一个悬而未决的问题。国家气象中心自从2009年将T639全球数值预报系统投入业务运行以来,应用了一套完整可行的台风初始化方案,其技术路线是在台风刚发生时的预报时刻,在背景场嵌入人造bogus涡旋;而在后续的循环滚动预报时刻,采取涡旋重定位和涡旋调整技术方案;因此,第一个预报时刻的涡旋形成技术直接影响到后续时刻的台风涡旋质量乃至预报效果。但是,人造bogus涡旋主要依据统计的经验模型建立,其结构与全球数值模式的动力学、物理学属性并不匹配。基于国家气象中心T639全球资料分析同化 预报循环系统,一套升级版的台风初始化方案被发展了起来,与业务方案的主要区别在于升级方案利用资料同化技术来形成初始涡旋而不是直接嵌入人造bogus涡旋;这在很大程度上减少了人为主观因素对台风初始结构的影响,而更多地是依靠变分资料同化来协调约束产生三维空间的涡旋环流,这样产生的涡旋环流不但与周围环境场比较协调,而且与模式的动力学、物理学属性也比较匹配。应用新方案,本文对生成于西北太平洋2011—2012年27个台风进行了数值试验,初步分析表明,新方案在实现台风初始涡旋环流结构方面有着不错的表现,相比于业务使用的方案而言,新方案台风路径平均预报误差有了不错幅度的降低,2~5 d预报平均路径误差普遍降低了3%~15%。
Abstract:Due to the lack of observational data over the tropical oceans, TC (tropical cyclone) initialization for numerical models is one of major difficulties in TC track forecasting. Since the National Meteorological Centre of China Meteorological Administration (NMC/CMA) put the global model T639 into operation in 2009, an effective TC initialization scheme has been used. When TC occurs at first cycle time, a bogus vortex is inserted into the background fields, which is called vortex formation. In the second, third, …, cycle time, the evolutive vortex generated with 6 h output of global model prediction at the previous time in the background fields is initialized by relocation (moving to observed position) and modification (adjusted to observed intensity) techniques. It is obvious that the vortex formation at the first cycle time is so important that it can affect the structure of TC and the forecast results of the subsequent cycle time. But the initial bogus vortex used in the first cycle time is not consistent with the dynamics and physics of the global model. Recently, a new vortex formation scheme based on T639 global analysis forecast cycle in NMC/CMA has been developed successfully. Compared with the operation scheme, the initial vortex of the new scheme is mostly formed by assimilating TC bogus data into the variational assimilation system. It is significant that the initial vortex structure is analyzed with constraint of variational method, not largely affected by the empirical and statistical manual factors. Meanwhile, the analyzed vortex is consistent with the dynamics and physics of the global model and also compatible with environmental flow in the boundary. To evaluate the impact of the new scheme on TC track predictions, more than 672 cases from 27 different TCs during 2011-2012 seasons are examined. The initial study result shows that, compared with operational scheme, the new scheme can generate reasonable and realistic vortex in the initial fields and produce TC track forecast more accurately. Statistical analysis shows a decrease in the average track error of 3%-15% during the 48-120 h time period.
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基金项目:公益性行业(气象)科研专项(201406006和201506002)共同资助
引用文本:
瞿安祥,麻素红,张进,2016.T639全球模式的台风初始化方案升级试验[J].气象,42(6):664-673.
QU Anxiang,MA Suhong,ZHANG Jin,2016.Updated Experiments of Tropical Cyclone Initialization in Global Model T639[J].Meteor Mon,42(6):664-673.