摘要
基于广州和深圳双多普勒雷达数据,对2008年6月6日发生在华南地区的一次准线状对流系统(QLCS)进行研究,分析其三维风场、动力和热力场结构并探讨其维持机制。结果表明:(1)QLCS初始于大范围层云降水中,在弱的大气不稳定环境下,存在中等强度的垂直风切变;QLCS发展时,地面有明显的中β尺度切变线,QLCS沿切变线组织成型,系统过境时地面水汽趋于饱和但未形成明显冷池。(2)发展成熟的QLCS的垂直上升速度区和正涡度区基本沿切变线呈带状,对流接近垂直发展,强回波区(>4dBz)多数发展至5km左右,但并未向系统移动前方倾斜,对流内的上升速度较小,最大上升速度(约6m·s^-1)在中高层,对流区内深厚的辐合形成于前侧低层(2km以下)和后侧深厚(维持到8km)的相对入流。(3)QLCS对流区内部为扰动高压,从低层到高层呈减小趋势;扰动位温数值很小,表明上升气流的浮力效应不明显;垂直动量诊断结果表明,对流维持的主要机制是扰动高压所产生的垂直气压梯度力。
A quasi-linear convection system(QLCS)in the stratiform region on 6 July 2008 has been investigated using dual-Doppler radar data collected from Guangzhou and Shenzhen.Three dimensional wind field,kinematic and thermodynamic structure are analysed and the maintenance mechanism of QLCS is discussed.The results are as follows.(1)The QLCS was formed in stratiform cloud precipitation region and has a moderate vertical wind shear with a weak unstable synoptic environment.The surface existed obvious meso-β-scale shear line during the QLCS development and the QLCS formed along the shear line.During the system passaged,water vapor was close to saturation without cold pool.(2)When the QLCS was in mature phase,the areas of vertical ascending motion and positive vorticity had banded structure,convections developed almost vertically,most of the strong radar(>4 dBz)echo developed to a height of about 5 km,and there was no tilting to the front of the system.The kinematic structures of the QLCS at the mature stage showed that their inside convective updrafts were smaller and the maximum value(6 m·s^-1)appeared at middle and high levels.Deep convergence formed by the relative influxes in the front low level(2 km or less)and the deep rear inflow(8 km)existed in the convection.(3)Inside the QLCS convections,there was a perturbation high with pressure decreasing from low to high levels.Very small perturbation potential temperature indicated that the buoyancy effect was weak.The vertical momentum budget calculation indicated that the vertical pressure gradient force produced by the perturbation pressure formed by convergence was the main mechanism for the convection maintenance.
作者
胡东明
魏超时
赵坤
周芯玉
张兰
HU Dongming;WEI Chaoshi;ZHAO Kun;ZHOU Xinyu;ZHANG Lan(Guangzhou Meteorological Observatory,Guangzhou 511430;Key Laboratory for Mesoscale Severe Weather/MOE and School of Atmospheric Science,Nanjing University,Nanjing 210093;Meteorological Center of East China Air Traffic Management Bureau CAAC,Shanghai 200335)
出处
《暴雨灾害》
2019年第3期193-203,共11页
Torrential Rain and Disasters
基金
国家自然科学基金项目(41875182)
国家重点研发计划项目(2017YFC1501701)
江苏省科技厅社会发展项目(BE2016732)
广东省科技计划项目(2017ZC0402)
广州市产学研协同创新重大专项(201704020169)
