冷涡背景下东北地区短时强降水统计特征

Statistical Analysis on Hourly Heavy Rainfall in Northeast China Induced by Cold Vortices

利用2011-2020年6-8月全国2400个地面自动站观测的逐小时降水资料和常规观测,结合美国NCEP/NCAR 1°×1°的6 h间隔再分析资料,基于站点统计了冷涡背景下东北地区短时强降水的时空分布特征。然后着眼降水落区,基于冷涡位置、形状、发展阶段以及与热带系统的相互作用等将冷涡短时强降水分为西北气流型、纬向型、南涡型、副高型和经向型,并讨论了5类短时强降水的对流参数特征。结果表明:6月,冷涡短时强降水多由中涡造成,7月和8月主要由北涡引起。短时强降水主要发生在午后,17:00(北京时)达到峰值。冷涡短时强降水高频区位于辽宁,次高频区位于吉林中部、黑龙江中西部和东北部。不同类型的短时强降水,其降水落区在冷涡不同发展阶段有所差异。冷涡短时强降水发生在条件不稳定的大气中,西北气流型、纬向型和经向型短时强降水的850 hPa与500 hPa温差一般大于25℃;副高型和南涡型短时强降水的850 hPa与500 hPa温差一般小于24℃,但地面露点和可降水量明显比其他3类大。5类短时强降水的对流有效位能一般不超过1500 J·kg^(-1)。大多数情况下,副高型短时强降水发生在中等强度的垂直风切变环境中,其他4类发生在弱的垂直风切变环境中。

By using hourly precipitation observation of automated weather stations,conventional observation and NCEP/NCAR 1°×1°reanalysis data from June to August during 2011-2020,a statistical analysis of the spatiotemporal characteristics of hourly heavy rainfall events caused by cold vortices in Northeast China was performed.Focusing on locations of rainfall,the hourly heavy rainfall events were classified into northwest airflow type(NW),zonal type(ZT),south vortex type(SV),subtropical high type(SH)and meridional type(MT)based on the position,shape and development stage of cold vortices as well as interaction with tropical systems.In addition,the features of convection parameters of these five types were studied.Results show that induced mostly by middle vortices in June,hourly heavy rainfall events were mainly caused by north vortices in July and August.The hourly heavy rainfall often occurred in the afternoon,reaching the peak at 17:00(Beijing Time).In the spatial distribution,the high frequency area of hourly heavy rainfall was situated in Liaoning Province,while the sub-high frequency area was located in the central Jilin Province and central-western and north-eastern Heilongjiang Province.The precipitation locations had differences not only in different types but also in phases of evolution of cold vortices.Moreover,hourly heavy rainfall events usually appeared in the conditional instability atmosphere.The temperature difference of NW,ZT and MT between 850 hPa and 500 hPa exceeded 25℃,while those of SH and SV were less than 24℃with higher dew point and larger precipitable water.The convective available energy of all types were relatively moderate,mostly less than 1500 J·kg^(-1).In most situation,the hourly heavy rainfall events of SH happened under moderate vertical wind shear,while others generally appeared in the environment with weak vertical wind shear.