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2012—2017年不同涡源西南低涡多发的影响因素分析

Analysis of influencing factors on frequent occurrence of Southwest China Vortexes with different vortex sources from 2012 to 2017

  • 摘要: 利用NCEP/FNL 1°×1°再分析资料、地面观测资料、高空探测资料和西南低涡年鉴,通过分析2012—2017年不同涡源西南低涡的活动情况,对九龙涡、盆地涡、小金涡生成时间最多月份的各低涡生成前与生成时的风场、其它物理特性合成场进行合成分析与对比分析,得出了环境风场、冷暖空气与锋生作用对九龙涡、盆地涡与小金涡生成的影响。结果表明:(1)3—6月是西南涡生成与移出涡源的多发时段,西南涡中以九龙涡为主,盆地涡次之,小金涡易移出涡源。(2)九龙涡、小金涡的生成与偏南气流流入各自涡区的开口地形有关,但小金涡流入的气流比九龙涡强,盆地涡生成与切变线有关。(3)九龙涡、小金涡的生成还受高原背风坡地面加热与西南气流影响,与暖平流区内有正的非热成风涡度有关,但九龙涡所处的暖平流区范围比小金涡的大,强度远不如小金涡,盆地涡的生成与涡区内有斜压性增强有关。(4)九龙涡、小金涡、盆地涡的生成与各自涡区内锋生强度增强有关,但各自影响锋生作用的因素不同,小金涡的生成主要受非绝热变化过程影响的锋生作用,九龙涡的生成受非绝热变化过程影响为主,以及水平、垂直运动共同影响的锋生作用,盆地涡的生成受垂直运动影响为主,以及非绝热变化过程共同影响的锋生作用。

     

    Abstract: Based on NCEP/FNL, surface observation and upper-air sounding data, and entries of the Southwest China Vortexes(SCVs) Yearbook, we analyzed the activities of Southwest China Vortexes with different vortex sources from 2012 to 2017. Composite and comparative analyses are conducted to the respective wind and other composite physical fields for the characteristics of Jiulong vortex, basin vortex and Xiaojin vortex prior and during the generation phase in the most frequent occurrence time of the year. The effects of background wind, cold and warm air flows, and frontogenesis on the generation of Jiulong vortex, basin vortex and Xiaojin vortex are then obtained. Results are as follows. (1) The main generation and moving period of SCV is from March to June. Jiulong vortex has the main role in SCV, followed by basin vortex. Xiaojing vortex is the least but has the biggest chance to move out of the source. (2) The formation of the Jiulong Vortex and the Xiaojin Vortex is related to the open shape topography of the southwest airflow flowing into their respective vortexes and the wind in Xiaojing vortex is stronger. The formation of the basin vortexes is related to the shear line. (3) The formation of Jiulong vortex and Xiaojin vortex is also related to the positive non-thermal wind vorticity in the warm advection area due to the influence of surface heating and southwest airflow on the leeward slope of the Plateau. However, the warm advection area of Jiulong vortex is larger than that of Xiaojin vortex, and its intensity is much lower than that of Xiaojin vortex. The formation of basin vortex is related to the stronger baroclinic effect of the cold air. (4) The formation of Jiulong vortex, Xiaojin vortex and basin vortex is all related to the enhancement of frontogenesis intensity of the respective vortex sources. But the factors influencing frontogenesis are different. The generation of Xiaojin vortex is mainly affected by the non-adiabatic pro?cess, and the formation of Jiulong vortex is mainly affected by the non-adiabatic change process, together with the horizontal and vertical motion of the airflow. The basin vortex generation is mainly affected by the vertical motion and the non-adiabatic also has some impact on it.

     

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