摘要
利用常规观测、地面自动气象站逐小时观测及NCEP/NCAR逐日4次1°×1°再分析等资料,对比分析2016年11月中旬新疆北部暖区暴雪过程中两个强降雪中心裕民与青河的物理量特征,重点讨论暴雪的动力耦合机制,结果表明:此次强降雪为典型暖区暴雪的天气系统配置,500 hPa高度上,新疆北部在西伯利亚低涡底部强锋区内,700 hPa和850 hPa有偏西低空急流和切变线,新疆北部受地面暖低压控制。上升运动和垂直螺旋度主要集中在700 hPa以下,低层辐合、中层辐散是上升运动的动力维持机制。两种情况下可使上升运动增强,降雪强度增大:一是当垂直螺旋度呈"上负下正"结构、垂直螺旋度的绝对值增大时;二是当暴雪区上空湿位涡MPV1呈"上正下负"结构、MPV2<0,且θse密集陡立带向暖区倾斜、垂直涡度增长时。涡度对上升运动的发展亦有正贡献。
Based on the data of routine observation,hourly observation by ground automatic weather station and NCEP/NCAR reanalysis 4 times a day,the physical quantity characteristics of Yumin and Qinghe,two heavy snowfall centers in the middle of November 2016,were compared and analyzed,and the dynamic coupling mechanism of heavy snowfall was mainly discussed.The results show that the heavy snowfall is a typical weather system configuration of heavy warm area snowfall,and the northern part of Xinjiang lies in the strong front area at the bottom of Siberian vortex at 500 hPa.There is low level jet and shear line to the west at 700 hPa and 850 hPa,and the northern part of Xinjiang is controlled by the surface warm low pressure.The ascending motion and vertical helicity are mainly concentrated below 700 hPa,and the lower level convergence and middle level divergence are the dynamic maintenance mechanisms of ascending motion.The ascending motion and snowfall intensity can be enhanced in two cases:one is when the vertical helicity is in the"up negative down positive"structure and the absolute value of the vertical helicity increases;the other is when the wet potential vorticity MPV1 over the blizzard area is in the"up positive down negative",MPV2<0,and the dense steepθsebelt inclines to the warm area and the vertical vorticity increases.Vorticity also contributes positively to the development of upward motion.
作者
李桉孛
李如琦
李娜
郑育琳
LI Anbei;LI Ruqi;LI Na;ZHENG Yulin(Xinjiang Meteorological Observatory,Urumqi 830002,China;College of Atmospheric Sciences,Chengdu University of Information Technology,Chengdu 610225,China)
出处
《沙漠与绿洲气象》
2020年第5期53-60,共8页
Desert and Oasis Meteorology
基金
新疆科技援疆项目(2019E0208).
关键词
暖区暴雪
动力特征
垂直结构
垂直螺旋度
湿位涡
warm sector snowstorm
dynamic characteristics
vertical structure
vertical helicity
moist potential vorticity
