【作者】 曹艳察；

【导师】 林永辉；

【作者基本信息】 中国气象科学研究院 ， 气象学， 2012， 硕士

【摘要】 利用高时空分辨率的地面观测资料、探空观测资料、多普勒雷达回波、TBB资料和雷达资料反演的风场数据以及NCEP再分析资料，对2010年6月19日发生在华南西部的一次飑线的演变过程和结构特征进行了分析研究。结果表明：（1）、飑线发生于200hPa高空辐散区、500hPa高空槽后、850hPa低空槽前的相对暖湿高值区，强对流位于地面辐合线及地面冷锋上，而不是锋前暖区；强对流形成区域大气呈现上冷下暖的典型不稳定层结特征。（2）、飑线最初起源于地面冷锋上的辐合线里的线状对流带，后与冷锋前暖区新生的线状对流合并，加强发展成为准东-西向的飑线系统。成熟期的飑线系统强对流区发展成为弓状回波，后部为包含中层回波亮带的层状云和两者之间的弱回波过渡带；地面出现雷暴高压和尾流低压。（3）、沿北部线状对流系统方向上的单体合并主要是对流单体间的下沉气流引起的辐合抬升导致的合并。两条对流带中单体的合并过程，则是由于南部暖区对流单体对应区域的强上升运动在高空形成辐散，其中一部分向北运动形成下沉气流，抑制了北部单体的发展，而北部下沉气流在低空的辐散又进一步促进了南部对流的低层辐合，在该垂直环流的作用下，南部单体不断发展，逐渐与北部对流系统合并。（4）、飑线系统中层弓状对流回波后部存在γ中尺度涡旋簇，弓状对流回波东-西两侧分别存在一个气旋式环流，回波中部则存在一个反气旋式环流；层状云区后部中层存在一个较大尺度的气旋式环流。弓状对流区前缘为倾斜上升气流，其后部弱回波过渡区是强烈的下沉气流，层状云中层存在较弱的尾部下沉入流，层状云上方为弱的上升运动。（5）、涡度分析表明飑线系统对流区的正涡度增长主要与垂直涡度的“拉伸项”的作用有关，对流区后部的负涡度区的变化主要受水平涡度的“倾斜项”的影响，层状云后部的正涡度区的变化主要受水平涡度的“倾斜项”的作用。更多还原

【Abstract】 Based on a variety of meteorological data (including the high spatial and temporal surfaceobservational data, sounding data, Doppler radar echo, TBB data, retrieval wind data of radarobservation and NCEP reanalysis data), the evolution and structure characteristics of a squallline occurred over the western part of South China on19thJune2010are investigated. Themajor conclusions are as follows:(1) The squall line is caused under the following situations:200hPa high-level divergence,rearward of500hPa trough, warm and moist area ahead of850hPa trough. The convectionlocates on the surface convergence line and cold front, instead of the warm section before thefront. In the region which the strong convection forms, the atmosphere appears a typicalunstable stratification with the cold air over the warm.(2) The squall line initially comes from a quasi-linear convective system along the surfaceconvergence line embedded in the cold front, subsequently combines with the newly triggeredquasi-linear convective system over the warming zone ahead of the cold front, and finallydevelops into the mature quasi east-west squall line system. At its mature stage, the leadingconvective line develops into a bowing echo, with a trailing stratiform region containing radarbright band at the mid-level and transition zone between them. Meanwhile, the thunderstormhigh and wake low form at the surface.(3) The convection cell merger process along the northern linear convection system ismainly caused by the convergence uplifting between downdraft in the adjacent cells. However,the merger process between the two convection lines is mainly due to the strong updraft in thesouthern convection cell, which triggering downdraft in the north with partial upper-leveldivergence airflow. By the action of the vertical circulation, the southern convection cellstrengthens while the northern one weakens, and gradually mergers with each other.(4) There are meso-γ bookend vortices along the convective bowing echo, including acyclonic vortex on the eastern and western flanks of the bowed segment and an anticyclonicvortex on the middle part of the bowing echo. Meanwhile, there is a larger scale cyclonic vortex in the rearward of the stratiform cloud. The squall line develops with updraft in theleading convective line and upper-levels of the stratiform region, as well as downdraft in thetransitional region and mid-to-lower levels of the stratiform cloud.(5) Vorticity budget analyses show that the positive vorticity along the convective regionforms mainly through the stretching of vertical vorticity, and the bookend vortices and thepositive vorticity in the rearward of the stratiform cloud form mainly through the tilting ofhorizontal vorticity.更多还原