摘要
2021年9月4日早晨,渤海湾西岸的天津滨海新区出现短时强降水,过程累计降雨量达224.2 mm,最大小时雨强为110.9 mm·h^(-1),均打破当地建站以来的历史纪录。利用加密自动气象观测站、风廓线雷达、多普勒雷达等观测资料,结合欧洲中期天气预报中心ERA5再分析资料,分析该事件成因及其与海陆环境的关系,探讨对流系统新生、组织化机制以及水汽输送特征等。结果表明:(1)对流单体在海岸线海水一侧新生后西移登陆,经多次与后向新生对流单体合并加强,最终发展为具有中γ尺度涡旋且位于线状中尺度对流系统前端的强降水系统。(2)对流单体新生地点与两条地面辐合线的相交点对应。一条南北向的风速辐合线位于海上,与水陆表面摩擦系数差异有关;另一条东西向的风向辐合线位于陆地,由东北残余冷空气与原有偏南风相遇而成。(3)由于清晨海面湿度比陆地大,湿空气被向岸偏东气流从渤海湾带到西岸,为对流系统的发生发展提供热力条件;而850 hPa持续存在暖性切变线,为多个对流系统线状组织排列提供了动力支持;值得关注的是,浅层残余弱冷空气在925 hPa造成明显的中尺度锋生。(4)次级垂直环流促进周围水汽汇集和垂直向上输送加强,而水汽垂直递减率的大小(水汽垂直辐合)对小时雨强有指示意义。分钟雨强很可能与中γ尺度涡旋有内在联系。
A short-time heavy precipitation process occurred in Binhai New Area,Tianjin on the west coast of Bohai Bay in the morning of 4 September 2021,with the accumulated rainfall of 224.2 mm and the maximum hourly rainfall intensity of 110.9 mm·h^(-1),which both break the station’s historical records since its foundation.Based on the observations of intensive automatic meteorological observing stations,wind profile radars and Doppler radars,as well as ERA5 data,the paper analyzes the causes of the event,its relationship with sea and land environment,convective initiation,organized mechanism,transfer of water vapor and so forth.The results are as follows.(1)The convective cell,born on the sea surface,moves westward to land,strengthens after merging with backward newborn convective cell,and finally develops into a heavy precipitation system with meso-γ-scale rotation at the front end of a linear mesoscale convective system.(2)Convective cells are triggered at the intersection of two surface convergence lines.One south-north wind speed convergence line,located on the sea surface,is related to the smaller friction coefficient of water surface than land.The other east-west wind direction convergence line,located on the land,is formed by the residual northeasterly cold air and original southerly.(3)In the morning,the humidity on the sea surface is higher than that on the land,so the warm and wet air is carried from Bohai Bay to its west coast by the boundary layer’s onshore easterly flow,which is a favorable thermal condition for the occurrence and development of the convective system near the coastline.At the same time,the persistent warm shear line at 850 hPa provides dynamic support for the convective system’s linear organized arrangement.It should be noticed that the residual weak cold air triggers meso-scale frontogenesis at 925 hPa.(4)The secondary vertical circulation promotes the accumulation and upward transfer of surrounding water vapor,and the lapse rate of water vapor(vertical convergence of water vapor)has indicative significance for hourly rainfall intensity.The minute rainfall intensity is probably intrinsically connected with the meso-γ-scale rotation.
作者
易笑园
陈宏
张庆
孙晓磊
胡潮
刘一玮
胡田田
YI Xiaoyuan;CHEN Hong;ZHANG Qing;SUN Xiaolei;HU Chao;LIU Yiwei;HU Tiantian(Tianjin Meteorological Observatory,Tianjin 300074,China;Tianjin Weather Modification Office,Tianjin 300074,China;Tianjin Central Observatory for Oceanic Meteorology,Tianjin 300074,China;Binhai New Area Meteorological Office of Tianjin,Tianjin 300457,China)
出处
《海洋气象学报》
2024年第3期1-13,共13页
Journal of Marine Meteorology
基金
国家自然科学基金项目(41575049,42375019)
天津市科技计划项目(22KPXMRC00080)
天津市海洋气象重点实验室开放基金项目(2024TKLOM05)。
关键词
极端强降水
向岸急流
触发维持
水汽垂直输送及递减率
中γ尺度涡旋
extremely heavy precipitation
onshore jet
initiation and maintenance
vertical transfer of water vapor and its lapse rate
meso-γ-scale rotation
