摘要
2017年7月21日上午,石家庄地区出现了一次局地暴雨过程,强降水主要集中在石家庄市区及其东部、北部,数值预报产品和主观预报均漏报了此次暴雨过程。本文利用地面加密自动站、多普勒雷达观测资料、雷达风廓线、多普勒雷达四维变分分析系统(VDRAS)以及NCEP再分析资料,分析了造成本次局地暴雨的中尺度对流系统(Mesoseale Convective Systems,MCSs)的触发机制,讨论了该系统的传播方向和影响整体运动的主要因子。结果表明:1)本次强降水发生前受“副高”588 dagpm线控制,降水区高温、高湿,为降水的发生积聚了大量不稳定能量。由于太行山在石家庄附近由东北-西南走向转为西北-东南走向,东北气流在此处逆转为西西北气流,从而在山前形成东北风和西西北风的辐合线;河北东北部秦皇岛、唐山地区因强降水形成较强的雷暴高压、冷池,雷暴高压产生的气压梯度力影响东北风逐渐加强,加强的东北风气流引导冷池呈舌状逐渐西南方向移动到石家庄北部地区,在前述辐合线附近形成低层辐合、中层辐散的不稳定层结,与西部太行山迎风坡对东北气流的强迫抬升共同作用,触发了不稳定能量的释放。2)本次过程前期雷暴在发展加强过程中,MCSs降水形成的雷暴冷出流东北方向移动,移速缓慢,在与环境东北气流辐合的区域,不断有新的雷暴触发,使得雷暴向东北方向传播,此阶段风暴承载层平均风(即MCSs的平移方向)风速较小,MCSs的移动平流不明显,以“后向传播”为主,系统稳定少动,表现为“准静止状态”;随着风暴承载层平均风风速的增加,MCSs的移动方向可以通过Corfidi矢量法,由低空急流的反向矢量和1.5 km以上(850~300 hPa)的平均风速矢量合成得到,且此阶段MCSs自身冷池的移动方向与风暴承载层平均风(西北风)密切相关,对应的雷暴冷出流东南方向移动,使得西北偏冷风冷池出�
On the morning of July 21,2017,a localized rainstorm event occurred in Shijiazhuang,with the heavy rain mainly concentrating in its urban area,eastern and northern parts,which was omitted by both numerical and subjective forecasts.In this paper,the triggering mechanisms of the mesoscale convective system(MCS)causing this rainstorm,the propagation direction of the system and the main factors affecting the overall movement were analyzed by using the intensified surface observation data,Doppler radar data,radar wind profile,the four-dimensional variational Doppler radar analysis system(VDRAS)and NCEP reanalysis data.The results show that:1)Before the heavy precipitation occurring,a large amount of unstable energy was accumulated because of the high temperature and high humidity in this area.The surface airflow was turned by Taihang Mountain in the vicinity of Shijiazhuang,forming the shear line of northeast wind and west-northwest wind in front of the mountain.The strong thunderstorm high and cold pool was formed by the heavy precipitation in Qinhuangdao and Tangshan areas.The pressure gradient force generated by the thunderstorm high strengthened the northeast wind,which guiding the cold pool to gradually move southwest in a tongue shape to the north of Shijiazhuang area.In the vicinity of the aforementioned shear line,an unstable stratification of low-level convergence and middle-level divergence was formed,which was combined with the topographic forced uplift of the windward slope triggering the unstable energy release.2)During the development and strengthening of thunderstorm,the cold outflow formed by the precipitation of MCS moved slowly in the northeast direction.In the area where the northeast airflow was converged,new thunderstorms were constantly triggered,which made thunderstorms spread northeast.At this stage,the average wind speed of the storm bearing layer(ie,the translation direction of the MCS)was small,the system was stable and less moving,mainly in the form of“backward propagation”,which was sh
作者
何丽华
王咏青
隆璘雪
闫雪瑾
耿飞
陈碧莹
张迎新
HE Lihua;WANG Yongqing;LONG Linxue;YAN Xuejin;GENG Fei;CHEN Biying;ZHANG Yingxin(Hebei Meteorological Observatory,Shijiazhuang 050021,China;Key Laboratory of Weather and Ecological Environment of Hebei Province,Shijiazhuang 050021,China;School of Atmospheric Sciences,Nanjing University of Information Science&Technology,Nanjing 210044,China;Xingtai Municipal Meteorological Bureau of Hebei Province,Xingtai 054000,China;Beijing Meteorological Station,Beijing 100081,China)
出处
《大气科学学报》
CSCD
北大核心
2020年第5期810-823,共14页
Transactions of Atmospheric Sciences
基金
国家重点研发计划专项项目(2018YFC1507305)
国家自然科学基金资助项目(41575049,41875070,41530427,41575040)
北极阁开放研究基金-南京大气科学联合研究中心(NJCAR2018MS02)
云南省重点研发计划-社会发展项目(2018BC007)
河北省科技计划(20375407D,17275409D)
河北省强对流团队共同资助
突发性强降水的模式产品释用技术研发及检验评估(2018YFC1507305)。
关键词
暖区暴雨
MCSS
冷池
地形
平流与传播
warm-sector rainstorm
MCSs
cold pool
terrain
advection and propagation
