承德市2015年2月20—21日强降雪成因分析  

Analysis of Heavy Snowfall Process in Chengde City on 20 to 21 February 2015

作　　者：杨杰 谭国明 尤国军 陆倩 刘园园 

机构地区：[1]承德市气象局,河北承德067000

出　　处：《沙漠与绿洲气象》2016年第4期32-38,共7页Desert and Oasis Meteorology

基　　金：河北省气象局预报员专项(14ky37)资助

摘　　要：利用常规观测资料、卫星云图和NECP(1°×1°)逐6 h再分析资料,对承德市2015年2月20—21日强降雪过程环流形势和物理量场进行分析。结果表明:中、低层西风槽、切变线和蒙古气旋共同构成有利天气形势,持续的西南气流对强降雪形成和维持至关重要。强降雪出现在斜压叶云系的暖侧。强降雪区上空相对湿度大且水汽供应充足,水汽通量变化与降雪变化相一致。强降雪区上空伴有强上升运动;整层为正涡度最有利于上升运动;垂直螺旋度整层为正或呈"上负下正"结构有利于降雪,低层正垂直螺旋度对强降雪变化有很好的指示意义。Based on conventional observational data, satellite cloud data, and NCEP/NCARreanalysis （1°×1°） , the atmospheric circulation features and physical mechanisms of heavy snowfallprocess in Chengde City on 20 to 21 February 2015 were analyzed. The results are as follows.Westerly trough and shear line at mid-low levels, as well as Mongolia cyclone at the surface arepropitious to the heavy snowfall. Sustained southwest warm moisture flux played a fundamental rolein the occurrence and maintenance of heavy snowfall. Heavy snowfall appear in baroclinic leafcloud warm side.The distribution of relative humidity and moisture flux indicates adequatesupplication of water vapor over the heavy snowfall area. During the process, the snowfall intensityincreased with moisture flux intensity. Evident ascending motion could be found from the heavysnowfall area .Heavy snowfall and ascending motion are most likely to occur when vorticity werepositive at all levels. The vertical distribution of vertical helicity, both“positive values at all levels”pattern or “negative value at high levels - positive value at low levels”pattern prompt heavysnowfall. Therefore, positive vertical helicity at lower levels is a good indicator of heavy snowfall.

关 键 词：强降雪 西南气流 水汽通量 涡度 垂直螺旋度 

分 类 号：P458.121[天文地球—大气科学及气象学]