江南地区一次持续性暴雨过程中中尺度对流系统模态研究
发布时间：2018-07-31 12:19
【摘要】：本文利用地面加密观测资料、探空资料、NCEP再分析资料和多普勒天气雷达组网拼图资料,结合中尺度模式WRF输出的高时空分辨率资料,研究了2014年6月19-22日发生在江南地区的一次持续性暴雨过程中中尺度对流系统(MCS)的演变过程、组织结构及模态转变机理。此次暴雨过程中,阻塞高压、副高、切变线及梅雨锋的稳定维持,为暴雨提供了稳定的大尺度环流背景,低空西南急流携带的暖湿气流与不断入侵的东北冷气流在江南地区交汇,低涡辐合与高层辐散耦合形成垂直环流,以及不断东移的短波槽,为暴雨提供了充足的水汽、动力及热力条件,有利于江南地区形成持续性暴雨。期间可分为三次暴雨过程:第一次过程属于锋前暖区暴雨,主要受第一个对流系统(MCS1)影响;第二次过程属于梅雨锋暴雨,主要受第二个对流系统(MCS2)影响;第三次过程也属于梅雨锋暴雨,受5个MCS持续不断的影响。MCS1属于PS型对流系统,对流系统发展演变过程中,受地面中尺度辐合线作用,低层表现为垂直对流线的相对入流,中高层表现为平行对流线的相对入流。MCS2演变过程中组织模态发生转变。对流东移发展中形成TS型MCS。在低涡推动下,逐渐转变为PS型MCS。环境风场上,TS型MCS表现为垂直对流线的相对入流,弓状回波北侧有气旋生成,PS型MCS的环流分布与MCS1一致。TS型MCS中,强对流区位于正扰动气压带,形成垂直作用于对流线的气压梯度力,导致相对入流垂直对流线;而在平行于对流线方向上,扰动气压变化小,平行相对气流较弱,整体呈现为较强的垂直向后的相对气流。在PS型MCS中,气压扰动整体表现为西南正气压扰动东北负气压扰动的分布特征,在西南东北向气压梯度力作用下,形成平行对流线向后的相对入流,导致MCS组织模态的转变。
[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.
【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】：P458.121.1
本文编号：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.
【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】：P458.121.1
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