摘要
利用NCEP/NCAR再分析逐日资料和其他常规观测资料,对2020年6月27日和7月7日湖北省两次低涡型极端降水气象因子异常特征进行对比分析。结果表明:两次过程均发生在梅雨期间,500 hPa中高纬均为两槽一脊型,低层均有低涡形成,整层水汽含量均呈明显的持续性异常特征,中心值较气候平均偏多2.5个标准差。6月27日过程极端降水主要出现在湖北省中西部,为西南低涡及地面热低压共同动力作用下形成的锋前暖区对流性降水过程。超低空急流中心强度较气候平均偏强达到3个标准差,暖低压发展的最低值较气候平均偏低2个标准差,对流有效位能达1000 J·kg^(-1)以上,超出气候平均达1.5个标准差,西南涡涡度正值与散度负值异常偏强同时叠加形成强烈上升运动。7月7日过程极端降水主要出现在湖北中东部,为江汉平原低涡与地面静止锋共同动力作用下形成的锋面型降水过程。华北冷高压异常偏强,较气候平均偏强约1个标准差,导致地面形成显著梅雨锋,江汉平原低涡前侧强辐合与地面静止锋相叠加,导致动力条件出现异常偏强,并稳定维持12 h左右。
Based on the daily NCEP/NCAR reanalysis data and other conventional observation data,the abnormal characteristics of meteorological factors of two extreme low-vortex precipitation in Hubei province on June 27 and July 7,2020,were compared and analyzed.The results show that the two processes both occurred during the Meiyu period,and the two-trough and one-ridge pattern appeared over the mid and high latitudes at 500 hPa,with low vortices being formed in the lower layers.The vapor in the whole layer showed obvious persistent abnormal characteristics,and the central value was 2.5 standard deviations higher than the climate average.The extreme precipitation occurred mainly in the central and western parts of Hubei province on June 27 was a convective precipitation process in the warm front area under the combined dynamic action of the southwest vortex and the surface thermal low pressure.The central intensity of the ultra-low level jet stream was three standard deviations stronger than the climatic average,and the lowest value of the development of the warm low was two standard deviations lower than the climatic average,with the convective available potential energy(CAPE)value reaching more than 1000 J·kg^(-1) and appearing 1.5 standard deviations higher than the climatic average.The positive vorticity and negative divergence of the southwest vortex were abnormally strong and superposition at the same time,forming a strong upward movement.The extreme precipitation occurred mainly in the central and eastern parts of Hubei province on July 7 was a frontal precipitation process formed by the combined dynamic action of a low vortex and ground stationary front in Jianghan plain.The anomalously strong cold high in North China,which was about one standard deviation above the climatic average,leads to the formation of a significant Meiyu front on the ground.The strong convergence in front of the low vortex in Jianghan plain is superimposed with the static front on the ground,resulting in abnormally strong dynamic conditions
作者
董良鹏
张萍萍
DONG Liang-peng;ZHANG Ping-ping(Wuhan Central Meteorological Observatory,Wuhan 430074,China;Weihai Meteorological Service,Weihai 264200,China)
出处
《气象与环境学报》
2022年第6期20-28,共9页
Journal of Meteorology and Environment
基金
湖北省气象局科技发展基金项目(2022Z01、2020Y02)资助。
关键词
梅雨
低涡
对流有效位能
Meiyu
Low vortex
Convective available potential energy(CAPE)
