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爆发性气旋的合成诊断及形成机制研究
RESEARCH ON COMPOSITE DIAGNOSIS AND MECHANISMS OF EXPLOSIVE CYCLONES
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摘要: 该文对发生在太平洋和大西洋的16个爆发性气旋作了合成分折, 对强弱爆发性气旋作了对比及诊断.研究发现, 基本场上存在不少明显的差异.分析得出, 强爆发性气旋的形成与高空急流的非纬向性以及反气旋性弯曲密切相关.非纬向高空急流为爆发性气旋提供了强的辐散、斜压性、斜压不稳定场.高层强爆发性气旋前部的反气旋曲率易造成重力惯性波在能量北传时发展, 促使气旋快速加深.暖平流及非绝热加热可使反气旋曲率加强.一般情况下, 当气旋西部位涡的大值区与北部位涡的大值区叠加下沉时, 有利于气旋爆发性发展.Abstract: In this paper, 16 explosive cyclones over Atlantic and Pacific oceans are analyzed. The "weak" and "strong" explosive cyclones are diagnosed and compared. It is found that the basic fields are different at many aspects. The formation of strong explosive cyclones is related to the non-zonal upper jet of anticyclonic curvature. The jet can cause the upper divergence fields and baroclinity and baroclinic instability as well as the development of internal gravity waves northward. The warm advection and diabatic heating can increase the curvature. In general, when the larger value centers of potential vorticity move toward the centers of explosive cyclones, it is advantageous to explosive cyclones.
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Key words:
- Pacific;
- Atlantic;
- Explosive cyclone;
- Composite diagnosis;
- Non-zonal upper jet
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图 1 太平洋、大西洋上, 爆发前, 200 hPa强、弱气旋温度场、高度场、风矢量场
(图中*为地面气旋所在位置 (下同), 虚线为等温线 (℃), 实线为等高线 (gpm) 箭头线为风矢量 (风速大小与箭头长短成正比) ), 左: 强气旋, 右: 弱气旋
图 3 爆发时, 大西洋上过气旋中心的涡度 (×10-5s-1) 东西向垂直剖面
(纵轴单位为 hPa, 横轴表示离地面气旋的距离 (×90 km) (下同) ), 左: 强气旋, 右: 弱气旋
图 4 (a) 大西洋上强气旋爆发前200 hPa θ场 (K) 分布
(图中箭头为n的方向, 其长短定性表示了的大小 (b) 大西洋上强气旋爆发前200～850 hPa (×10-3s-1)分布, 图中箭头为n的方向)
表 1 16个爆发性气旋的强度和爆发时及其前后地面气旋的位置
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