2016年初辽宁一次暴雪过程中锋生作用分析

Analysis of the Role of Frontogenesis in A Blizzard in Liaoning in Early 2016

应用NCEP FNL分析资料,对2016年初辽宁地区一次暴雪过程预报偏差的形成机理进行了分析。结果表明:暴雪过程强降雪区域伴有锋生活动,锋生是暴雪增强的直接原因。降雪期间出现持续锋生,总锋生函数随时间向高层发展,在强降雪阶段水平变形项对锋生起正贡献,水平散度项起锋消作用。锋生作用下,锋面次级环流加强,利于水平辐合增强进而导致正涡度发展,对上升运动有正反馈作用,利于上升运动的维持,使得动力抬升和水汽辐合作用增强导致强降雪天气,是导致降雪量预报偏差的主要原因。

Using NCEP FNL analysis data,the formation mechanism of prediction deviation in a blizzard process in Liaoning area in early 2016 was analyzed.The results show that during the heavy snowfall,the snowfall area is accompanied by frontogenesis,which is the direct cause of the increase of heavy snowfall.Continuous snowfall occurred during frontogenesis,the total frontogenesis function develops to the high level over time.In the heavy snowfall period,horizontal deformation termplays a positive role while horizontal divergence termplays a negative role.Under the frontogenesis,the frontal secondary circulation is strengthened,which facilitates the enhancement of horizontal convergence and lead to the positive vorticity development.It hasa positive feedback effect on the upward movement to maintain the upward motion.Therefore,the dynamic lifting and convergence effect leads to the increase of heavy snowfall,which is a major cause of snowfall forecast deviation.