江南地區(qū)一次持續(xù)性暴雨過程中中尺度對流系統模態(tài)研究
發(fā)布時間：2018-07-31 12:19
【摘要】：本文利用地面加密觀測資料、探空資料、NCEP再分析資料和多普勒天氣雷達組網拼圖資料,結合中尺度模式WRF輸出的高時空分辨率資料,研究了2014年6月19-22日發(fā)生在江南地區(qū)的一次持續(xù)性暴雨過程中中尺度對流系統(MCS)的演變過程、組織結構及模態(tài)轉變機理。此次暴雨過程中,阻塞高壓、副高、切變線及梅雨鋒的穩(wěn)定維持,為暴雨提供了穩(wěn)定的大尺度環(huán)流背景,低空西南急流攜帶的暖濕氣流與不斷入侵的東北冷氣流在江南地區(qū)交匯,低渦輻合與高層輻散耦合形成垂直環(huán)流,以及不斷東移的短波槽,為暴雨提供了充足的水汽、動力及熱力條件,有利于江南地區(qū)形成持續(xù)性暴雨。期間可分為三次暴雨過程:第一次過程屬于鋒前暖區(qū)暴雨,主要受第一個對流系統(MCS1)影響;第二次過程屬于梅雨鋒暴雨,主要受第二個對流系統(MCS2)影響;第三次過程也屬于梅雨鋒暴雨,受5個MCS持續(xù)不斷的影響。MCS1屬于PS型對流系統,對流系統發(fā)展演變過程中,受地面中尺度輻合線作用,低層表現為垂直對流線的相對入流,中高層表現為平行對流線的相對入流。MCS2演變過程中組織模態(tài)發(fā)生轉變。對流東移發(fā)展中形成TS型MCS。在低渦推動下,逐漸轉變?yōu)镻S型MCS。環(huán)境風場上,TS型MCS表現為垂直對流線的相對入流,弓狀回波北側有氣旋生成,PS型MCS的環(huán)流分布與MCS1一致。TS型MCS中,強對流區(qū)位于正擾動氣壓帶,形成垂直作用于對流線的氣壓梯度力,導致相對入流垂直對流線;而在平行于對流線方向上,擾動氣壓變化小,平行相對氣流較弱,整體呈現為較強的垂直向后的相對氣流。在PS型MCS中,氣壓擾動整體表現為西南正氣壓擾動東北負氣壓擾動的分布特征,在西南東北向氣壓梯度力作用下,形成平行對流線向后的相對入流,導致MCS組織模態(tài)的轉變。
[Abstract]:In this paper, the ground encrypted observation data, the sounding data, the NCEP reanalysis data and the Doppler weather radar netting jigsaw data are used, and the high spatial and temporal resolution data from the mesoscale model WRF are combined. The evolution, structure and modal transformation mechanism of mesoscale convective system (MCS) during a persistent rainstorm in the south of the Yangtze River from June 19-22, 2014 were studied. During the rainstorm, the blocking high, subtropical high, shear line and Meiyu front were maintained steadily, which provided a stable large-scale circulation background for the heavy rain. The warm and wet air flow carried by the low altitude southwest jet stream and the invading northeast cold air flow meet in the south of the Yangtze River. The coupling of the convergence of the low vortex and the divergence of the upper layer forms the vertical circulation, and the short-wave trough moving eastward, which provides sufficient water vapor for the rainstorm. Dynamic and thermal conditions are conducive to the formation of persistent rainstorms in the south of the Yangtze River. It can be divided into three rainstorm processes: the first process belongs to the front warm region rainstorm, which is mainly influenced by the first convective system (MCS1), the second process belongs to the Meiyu front rainstorm, which is mainly influenced by the second convective system (MCS2). The third process also belongs to Meiyu front rainstorm, which is influenced by 5 MCS continuously. MCS1 belongs to PS type convection system. During the development and evolution of convective system, the lower layer is characterized by vertical relative inflow of streamlines due to mesoscale convergence line on the ground. In the middle and high levels, the transition of organizational modes occurs during the evolution of parallel pair streamlines relative to inflow. MCS2. TS type MCSs were formed during the eastward movement of convection. Under the impelling of low vortex, it is gradually transformed into PS type MCS. In the wind field, TS-type MCS shows a relative inflow of vertical opposite streamlines, and the circulation distribution of PS type MCS on the north side of the bow echo is consistent with that of MCS1 .TS type MCS, and the strong convection zone is located in the positive disturbed pressure zone. The pressure gradient force acting perpendicular to the streamlines leads to the vertical opposite streamlines relative to the inflow lines, while in the direction parallel to the counter-streamlines, the disturbance pressure changes little, the parallel relative airflow is weak, and the whole presents a relatively strong vertical backward relative airflow. In PS type MCS, the whole pressure disturbance is the distribution characteristic of the southwest positive pressure disturbance and the northeast negative pressure disturbance. Under the action of the northeast southwest pressure gradient force, the relative inflow parallel to the streamline leads to the change of the MCS organizational mode.
【學位授予單位】：中國氣象科學研究院
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P458.121.1
本文編號：2155564
[Abstract]:In this paper, the ground encrypted observation data, the sounding data, the NCEP reanalysis data and the Doppler weather radar netting jigsaw data are used, and the high spatial and temporal resolution data from the mesoscale model WRF are combined. The evolution, structure and modal transformation mechanism of mesoscale convective system (MCS) during a persistent rainstorm in the south of the Yangtze River from June 19-22, 2014 were studied. During the rainstorm, the blocking high, subtropical high, shear line and Meiyu front were maintained steadily, which provided a stable large-scale circulation background for the heavy rain. The warm and wet air flow carried by the low altitude southwest jet stream and the invading northeast cold air flow meet in the south of the Yangtze River. The coupling of the convergence of the low vortex and the divergence of the upper layer forms the vertical circulation, and the short-wave trough moving eastward, which provides sufficient water vapor for the rainstorm. Dynamic and thermal conditions are conducive to the formation of persistent rainstorms in the south of the Yangtze River. It can be divided into three rainstorm processes: the first process belongs to the front warm region rainstorm, which is mainly influenced by the first convective system (MCS1), the second process belongs to the Meiyu front rainstorm, which is mainly influenced by the second convective system (MCS2). The third process also belongs to Meiyu front rainstorm, which is influenced by 5 MCS continuously. MCS1 belongs to PS type convection system. During the development and evolution of convective system, the lower layer is characterized by vertical relative inflow of streamlines due to mesoscale convergence line on the ground. In the middle and high levels, the transition of organizational modes occurs during the evolution of parallel pair streamlines relative to inflow. MCS2. TS type MCSs were formed during the eastward movement of convection. Under the impelling of low vortex, it is gradually transformed into PS type MCS. In the wind field, TS-type MCS shows a relative inflow of vertical opposite streamlines, and the circulation distribution of PS type MCS on the north side of the bow echo is consistent with that of MCS1 .TS type MCS, and the strong convection zone is located in the positive disturbed pressure zone. The pressure gradient force acting perpendicular to the streamlines leads to the vertical opposite streamlines relative to the inflow lines, while in the direction parallel to the counter-streamlines, the disturbance pressure changes little, the parallel relative airflow is weak, and the whole presents a relatively strong vertical backward relative airflow. In PS type MCS, the whole pressure disturbance is the distribution characteristic of the southwest positive pressure disturbance and the northeast negative pressure disturbance. Under the action of the northeast southwest pressure gradient force, the relative inflow parallel to the streamline leads to the change of the MCS organizational mode.
【學位授予單位】：中國氣象科學研究院
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P458.121.1
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