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气象:2016,42(3):294-304
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一次温带气旋涡度场演变特征及气旋发生发展机制分析
(1.中国气象局气象干部培训学院,北京 100081;2.北京大学物理学院,北京 100871)
An Analysis of Vorticity Evolution and Physics Mechanism on an Extratropical Cyclone
(1.China Meteorological Administration Training Centre, Beijing 100081;2.Physics School, Peking University, Beijing 100871)
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投稿时间:2015-05-28    修订日期:2015-12-03
中文摘要: 气旋是涡旋运动,因此相对涡度(以下简称涡度)是确切表征气旋中心位置和强度的物理量,分析气旋发生发展过程就是分析涡度的变化机理。文中采用1000 hPa地转风涡度表征地面气旋,利用常规地面观测、6 h一次的NCEP 1°×1°再分析场等资料,对2014年6月一次具有螺旋式回转路径的北方温带气旋过程进行了诊断分析。利用Petterssen地面气旋发展公式,再结合300 hPa涡度平流、散度场与850 hPa热力场的配置关系,考察了对流层中低层温度平流、500 hPa涡度平流以及300 hPa涡度平流引起的辐散对地面气旋发展的贡献。结果表明:(1)这次气旋过程中500、300 hPa 存在两个正涡度区及涡度中心的替换:即在地面气旋发生发展阶段,第一个涡度中心为主要的涡度中心;在气旋减弱阶段,第二个涡度中心成为主要的涡度中心。(2)地面和高空涡度中心均以逆时针螺旋式路径移动。在地面气旋初生和发展阶段,高低层涡度中心及正涡度区呈后倾结构;当高低层涡度中心及正涡度区几乎垂直重合时,地面气旋停止发展。(3)温度平流项在气旋初生阶段起主要作用;500 hPa涡度平流决定了地面气旋的发展。(4)当300 hPa正涡度平流引起的辐散区叠加在对流层低层850 hPa斜压锋区上时,地面气旋发展。
Abstract:As cyclone is vortex, the parameter relative vorticity (for brevity, vorticity) can be used to exactly describe the position and intensity of extratropical cyclone. Thus, the research of the extratropical cyclone development is actually the mechanism analysis of vorticity. With the geostrophic wind vorticity at 1000 hPa adopted in this study, a typical extratropical cyclone with a spiral track occurred during 6-10 June 2014 is diagnosed using conventional observations and NCEP 1°×1° reanalysis data. Based on Petterssen’s equation, and the configuration of positive vorticity advection and divergence at 300 hPa and thermal advection at 850 hPa, this paper investigates the contributions of thermal advection in middle lower layer of troposphere, the vorticity advection at 500 hPa and the divergence induced by the vorticity advection at 300 hPa to the development of surface cyclone. The results show that: (1) Vorticity transferred between 2 positive vorticity zones at 300 hPa and 500 hPa. The first positive vorticity zone was the main one during cyclogenesis and development while the other became dominant in the decaying period. (2) In the whole troposphere, the vorticity centers moved cyclonically on a curve path. During the development of the surface cyclone, the positive vorticity centers tilted rearward with height, and while weakening, they were vertically overlapped at different levels. (3) The temperature advection played a major role in cyclogenesis while positive vorticity advection at 500 hPa was the main factor in the cyclonic development. (4) Cyclone would develop when the divergence caused by positive vorticity advection at 300 hPa was located above the frontal zone at 850 hPa.
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基金项目:国家自然科学基金项目(41405007)和中国气象局预报员专项(CMAYBY2015 096和CMAYBY2015 097)共同资助
引用文本:
熊秋芬,张昕,陶祖钰,2016.一次温带气旋涡度场演变特征及气旋发生发展机制分析[J].气象,42(3):294-304.
XIONG Qiufen,ZHANG Xin,TAO Zuyu,2016.An Analysis of Vorticity Evolution and Physics Mechanism on an Extratropical Cyclone[J].Meteor Mon,42(3):294-304.