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气象:2019,45(1):38-49
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台风苏迪罗登陆次日分散性暴雨成因及预报着眼点
杨舒楠,曹勇,陈涛,唐健,郭云谦
(国家气象中心,北京 100081)
Causes and Focus Points of Forecasting the Scattered Rainstorm of Typhoon Soudelor on Day 2 After Landing
YANG Shunan,CAO Yong,CHEN Tao,TANG Jian,GUO Yunqian
(National Meteorological Centre, Beijing 100081)
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投稿时间:2017-02-07    修订日期:2018-11-26
中文摘要: 利用常规气象观测,卫星、雷达资料,数值模式和中央气象台定量降水预报数据以及FNL分析数据等对台风苏迪罗的定量降水预报进行检验,探讨台风登陆次日分散性暴雨成因和预报着眼点。苏迪罗登陆次日,暴雨分布相对较分散,各家数值模式对其把握均较差。NMC的24 h定量降水预报虽在模式基础上有较好订正,但仍存在明显的暴雨空、漏报现象:暴雨落区预报较实况偏南,导致南侧空报、北侧漏报。受环境场和台风非对称结构影响,强降水产生的有利动力、水汽条件均位于台风北侧和东部沿海地区。台风东北象限对流层低层存在两条强辐合带,其间为降水较弱的弱辐散和下沉运动区。预报员对台风结构的非对称性及风场的非均匀性把握不足,对台风中心附近和两条辐合带间的弱降水区预报偏强,造成暴雨空报。在地形作用下,浙江沿海不断有强降水产生,随后沿切线方向发展为螺旋雨带并逐渐北扩。预报员对地形不断强迫作用下降水沿螺旋雨带的发展及向外围的扩散没有预期,导致浙江北部暴雨漏报。台风登陆次日分散性暴雨的预报着眼点包括:台风非对称性、风场非均匀性、螺旋雨带发展及地形作用等。非对称性影响较大尺度的降水落区;低层风场非均匀的辐合带及急流分布则引起螺旋雨带的发展、演变,决定了台风的精细强降水落区。除地形对局地降水具有增幅作用外,强降水沿螺旋雨带的发展还会对下游地区产生影响。
Abstract:Conventional observation data, quantitative precipitation forecast (QPF) data of numerical weather prediction (NWP) models and NMC forecasters, and NCEP FNL analysis data are employed to verify the QPF and study the causes and forecast focus of the scattered rainstorm of Typhoon Soudelor on Day 2 after landing. On Day 2, rainstorm of Typhoon Soudelor was relatively scarred. QPF of NWP mo dels all had obvious errors. Although 24 h QPF produced by NMC got many good corrections compared with numerical models, it still showed false heavy rainfall alarm or missed rainstorm in detail. Because of the forecasted location of rainstorm was more southerly than observation, there exited false alarm on the south side and missed rainstorm on the north side of the heavy rainfall. Impacted by environmental conditions and asymmetric structure of the typhoon, the favorable dynamical and water vapor conditions distri buted in the north side of the typhoon and the eastern coastal areas. There were two strong convergence belts in low level troposphere in northeast quadrant of typhoon. Between the two convergent belts, weak low level divergence and downward motion were seen leading to much weaker rainfall in this area. Forecasters underestimated the asymmetry of typhoon structure and the inhomogeneity of wind field. So, for the weak rainfall area around the typhoon center and between two convergence belts, they obviously overestimated. Induced by topographic effect, heavy rainfall emerged continuously in Zhejiang coastal areas. And then the rainstrom evolved into a spiral rainband along tangential direction and extended northward. Forecasters omitted the tangential evolution and outward transportation of spiral rainband forced by terrain continuously, which resulted in the missing of rainstorm in the north of Zhejiang. The forecast key points of the Day 2 scattered rainstorm included typhoon’s asymmetric structure, non homogeneous distribution of wind, evolution of spiral rainband and terrain effect, etc. Larger scale heavy rainfall distributions were decided by the asymmetric structure of typhoon, while for refined locations of rainstorm, the evolution of spiral rainband influenced by non homogeneous low level convergence and location of low level jet was very important. Thus, terrain can not only amplify rainfall in local areas, but also have effects on downstream heavy rainfall.
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基金项目:国家重点研发计划(2017YFC1502502)、国家自然科学基金项目(41405051)和国家气象中心预报员专项(Y201704)共同资助
引用文本:
杨舒楠,曹勇,陈涛,唐健,郭云谦,2019.台风苏迪罗登陆次日分散性暴雨成因及预报着眼点[J].气象,45(1):38-49.
YANG Shunan,CAO Yong,CHEN Tao,TANG Jian,GUO Yunqian,2019.Causes and Focus Points of Forecasting the Scattered Rainstorm of Typhoon Soudelor on Day 2 After Landing[J].Meteor Mon,45(1):38-49.