两类不同深厚型低涡结构特征及成因分析

发布时间：2019-05-27 11:36

【摘要】：本文总结了之前对于西南地区低涡的结构特征和发展机理研究,指出之前对于我国西南地区低涡系统如高原涡、西南涡在其结构上认识的薄弱点,如认为西南地区的低涡系统为浅薄系统。在此基础上,主要针对一类深厚型低涡系统的环流背景、热力动力结构、涡度收支和能量转换等方面进行分析,挑选出两个典型个例进行综合对比研究,得到的主要结论如下:(1)在环流背景方面,两次深厚型低涡的发生发展与高层南亚高压、东部大槽有关,都发生于南压高压位置偏西、强度偏弱,东部大槽深厚南伸明显的时期。(2)在动力结构上,深厚型高原涡向上发展,中心轴线垂直,形成阶段辐合弱,涡区内主要为下沉运动,正涡度区深厚;深厚型冷涡向下发展,中心轴线由随高度降低向东南倾斜逐渐转为垂直,水平风场结构呈非对称性,上升运动不断增加,正涡度区也向东南倾斜。(3)热力性质上,两次深厚低涡都具有分层性,在200hPa等压面上为暖性,暖心的形成与南亚高压暖平流有关,200hPa以下为冷性。深厚型高原涡由于初生时是暖性低涡,在之后的发展过程中逐渐转为冷性,且不同高度的冷性结构形成顺序不同;深厚型冷涡在向下发展的过程,冷心已经先于低涡形成,并位于低涡西侧,之后低涡向冷心发展。(4)两次深厚低涡过程都加剧了大气不稳定条件,引起了强对流天气,但由于水汽条件和低涡热力性质的不同,所产生的强对流天气也不同。(5)在深厚型低涡发展过程中,深厚型冷涡不同高度上的低涡发展因子不尽相同,但都与水平辐合关系密切,其次与垂直输送有关,但在不同阶段和不同高度仍有区别。(6)在低涡能量演变中,深厚型高原涡由于产生强降水天气,其凝结潜热的释放和高层高动量空气随高空急流下沉支传递到中低层,对维持该高原涡的有重要作用。深厚型冷涡发展过程中,有明显的扰动动能和扰动有效位能的下传,特别是扰动有效位能的下传,对中层高扰动有效位能的维持作用重大。但是在深厚型冷涡的不同阶段,其扰动动能和扰动有效位能的主要发展因子并不一样。
[Abstract]:In this paper, the structural characteristics and development mechanism of the vortex in southwest China are summarized, and the weak points in the structure of the vortex system in southwest China, such as the plateau vortex, are pointed out. It is considered that the vortex system in southwest China is shallow. On this basis, the circulation background, thermodynamic dynamic structure, vorticity budget and energy conversion of a class of deep thick low vortex systems are analyzed, and two typical cases are selected for comprehensive comparative study. The main conclusions are as follows: (1) in the circulation background, the occurrence and development of the two deep and thick vortexes are related to the upper South Asian high and the eastern trough, both of which occur in the westward and weak intensity of the southerly high pressure. The deep and southern extension of the eastern trough is obvious. (2) in the dynamic structure, the deep and thick plateau vortex develops upward, the central axis is vertical, the convergence stage is weak, the vortex area is mainly subsidence movement, and the positive vorticity area is deep; The deep thick cold vortex develops downward, the central axis tilts from southeast to vertical with the decrease of height, the horizontal wind field structure is asymmetrical, the rising motion increases, and the positive vorticity region also tilts southeast. (3) in terms of thermodynamic properties, The two deep vortexes are layered and warm on the 200hPa isobaric surface. The formation of warm centers is related to the warm advection of the South Asian high and cold below 200hPa. Because the deep and thick plateau vortex is warm and low vortex at birth, it gradually becomes cold in the process of subsequent development, and the formation order of cold structure at different heights is different. In the process of the downward development of the deep and thick cold vortex, the cold center has been formed before the low vortex, and is located on the west side of the low vortex, and then the low vortex develops to the cold center. (4) both deep vortex processes aggravate the atmospheric instability conditions and cause severe convective weather. However, due to the different thermal properties of water vapor and vortex, the severe convective weather is also different. (5) in the process of the development of deep and thick vortex, the development factor of low vortex at different height of deep and thick cold vortex is different. However, they are closely related to horizontal convergence, followed by vertical transport, but there are still differences in different stages and heights. (6) in the evolution of low vortex energy, the deep and thick plateau vortex produces heavy precipitation weather. The release of condensation latent heat and the transfer of high momentum air to the middle and lower levels with the sinking branch of the upper jet play an important role in maintaining the plateau vortex. In the process of the development of deep thick cold vortex, there are obvious downward propagation of perturbed kinetic energy and perturbed effective potential energy, especially the downward transmission of perturbed effective potential energy, which plays an important role in maintaining the high perturbed effective potential energy in the middle layer. However, in different stages of the thick cold vortex, the main development factors of the perturbed kinetic energy and the perturbed effective potential energy are not the same.
【学位授予单位】：中国气象科学研究院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P458.1

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