渤海湾北部地区冰雹天气分型及预报方法研究

Basic Synoptic Situation Classification and Forecasting Methods of Hail in the Northern Bohai Bay

利用常规观测和区域自动气象站资料,对2000—2016年渤海湾北部地区5—11月出现的32次冰雹过程进行天气学分型,对比不同类型冰雹天气的环境参数特征,得出相应的预报方法。结果表明:渤海湾北部地区冰雹主要分为高空干冷气流强迫型及斜压锋生型。前者受对流层中高层的干冷平流强迫,配合中尺度低压及地面辐合线,午后近地面的太阳辐射加热起到关键作用(简称干冷强迫型);后者主要发生于低涡槽前的锋面气旋冷锋附近,锋面动力强迫是此类冰雹的主要触发机制(简称锋生型)。干冷强迫型较锋生型表现出更强的静力不稳定层结、更大的风向垂直切变、相对较低的低层湿度和0℃层高度与-20℃层高度。渤海湾北部地区降雹多发生于东北冷涡天气背景之下,湿度条件高于西北地区、低于中东部地区,层结不稳定度高于中东部地区、低于西北地区。除中低层温度直减率、中层干层、低层湿层及深层垂直风切变等常用指标外,湿球0℃层高度及逆温层高度对渤海湾北部地区冰雹天气发生有着较好的指示意义。选取以上预报因子,运用指标叠套法对2017、2018年5—11月进行冰雹潜势预报,降雹过程无漏报,TS评分高于国家级强对流主观预报。

Based on the conventional and surface automatic weather station(AWS)observations,32 hails events that occurred in the northern part of the Bohai Bay from May to November during 2000-2016 was classificated with synoptical meteorology.The characteristics of environmental parameters about different types of hail were compared to research the hail forecast method.The results show that the hail in the northern Bohai Bay is mainly divided into dry-cold advection forcing category and baroclinic frontogenesis category.The former’s typical characteristics is the mid-upper dry-cold advection forcing above and the boundary warm convergence zone,where the surface inhomogeneous local heating play major roles(Referred to as dry-cold advection forcing category).The latter mainly occurs in the frontal cyclone,and the dynamic foring of cold front is the main trigger mechanism(Referred to as frontogenesis category).The dry-cold forcing category shows a stronger static instability layer,a larger SHRL,a lower humidity at low layer,and a lower 0℃,-20℃layer height.The number of hails under background of the cold vortex are more in northeast China.Compared with northwest China and mid-eastern China,the water vapor condition is in the middle,and the static stability is stronger than that in mid-eastern China but weaker than that in northwest China.In addition to the commonly used parameters such asΔT850-500,(T-Td)500,(T-Td)850,Min(T-Td)l,Max(T-Td)h,SHRL,WBZ and IZH have a good indication on the occurrence of hail in the northern Bohai Bay.By selecting forecasting factors,the fold set of method is used for hail potential forecast from May to November during 2017-2018.The result show no missing forecast,which has higher TS score than that by the national-level strong convective.