【摘要】：本文總結(jié)了之前對于西南地區(qū)低渦的結(jié)構(gòu)特征和發(fā)展機(jī)理研究,指出之前對于我國西南地區(qū)低渦系統(tǒng)如高原渦、西南渦在其結(jié)構(gòu)上認(rèn)識的薄弱點(diǎn),如認(rèn)為西南地區(qū)的低渦系統(tǒng)為淺薄系統(tǒng)。在此基礎(chǔ)上,主要針對一類深厚型低渦系統(tǒng)的環(huán)流背景、熱力動(dòng)力結(jié)構(gòu)、渦度收支和能量轉(zhuǎn)換等方面進(jìn)行分析,挑選出兩個(gè)典型個(gè)例進(jìn)行綜合對比研究,得到的主要結(jié)論如下:(1)在環(huán)流背景方面,兩次深厚型低渦的發(fā)生發(fā)展與高層南亞高壓、東部大槽有關(guān),都發(fā)生于南壓高壓位置偏西、強(qiáng)度偏弱,東部大槽深厚南伸明顯的時(shí)期。(2)在動(dòng)力結(jié)構(gòu)上,深厚型高原渦向上發(fā)展,中心軸線垂直,形成階段輻合弱,渦區(qū)內(nèi)主要為下沉運(yùn)動(dòng),正渦度區(qū)深厚;深厚型冷渦向下發(fā)展,中心軸線由隨高度降低向東南傾斜逐漸轉(zhuǎn)為垂直,水平風(fēng)場結(jié)構(gòu)呈非對稱性,上升運(yùn)動(dòng)不斷增加,正渦度區(qū)也向東南傾斜。(3)熱力性質(zhì)上,兩次深厚低渦都具有分層性,在200hPa等壓面上為暖性,暖心的形成與南亞高壓暖平流有關(guān),200hPa以下為冷性。深厚型高原渦由于初生時(shí)是暖性低渦,在之后的發(fā)展過程中逐漸轉(zhuǎn)為冷性,且不同高度的冷性結(jié)構(gòu)形成順序不同;深厚型冷渦在向下發(fā)展的過程,冷心已經(jīng)先于低渦形成,并位于低渦西側(cè),之后低渦向冷心發(fā)展。(4)兩次深厚低渦過程都加劇了大氣不穩(wěn)定條件,引起了強(qiáng)對流天氣,但由于水汽條件和低渦熱力性質(zhì)的不同,所產(chǎn)生的強(qiáng)對流天氣也不同。(5)在深厚型低渦發(fā)展過程中,深厚型冷渦不同高度上的低渦發(fā)展因子不盡相同,但都與水平輻合關(guān)系密切,其次與垂直輸送有關(guān),但在不同階段和不同高度仍有區(qū)別。(6)在低渦能量演變中,深厚型高原渦由于產(chǎn)生強(qiáng)降水天氣,其凝結(jié)潛熱的釋放和高層高動(dòng)量空氣隨高空急流下沉支傳遞到中低層,對維持該高原渦的有重要作用。深厚型冷渦發(fā)展過程中,有明顯的擾動(dòng)動(dòng)能和擾動(dòng)有效位能的下傳,特別是擾動(dòng)有效位能的下傳,對中層高擾動(dòng)有效位能的維持作用重大。但是在深厚型冷渦的不同階段,其擾動(dòng)動(dòng)能和擾動(dòng)有效位能的主要發(fā)展因子并不一樣。
[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.
【學(xué)位授予單位】：中國氣象科學(xué)研究院
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：P458.1

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