一次极端春季暴雪过程风场结构特征的演变分析

Analysis on Evolution Characteristic of Wind Field Structure of an Extreme Spring Blizzard Process

利用常规观测资料及风廓线雷达资料分析了2013年4月19日山东境内一次极端春季暴雪过程。结果表明,此次过程是一次明显的回流形势,低层冷垫形成以后,中高层的暖湿空气在冷垫上爬升是此次过程产生的有利环流背景;850 h Pa高度附近的准静止垂直切变是一个关键系统,它自产生到结束长达近9 h;当垂直切变的高度维持在1.5 km,上下的风向为西北风与偏南风的切变时,降水性质为雨或雨夹雪;当垂直切变的高度猛然下压至1.2 km,上下的风向变为西北风与偏东风的切变时,降水性质为纯雪。切变线消失之后,600 m以下的中小尺度系统又对降雪起到了持续触发作用。4月中旬地面温度偏高,结合此次过程可知,当地面温度和1 000 h Pa降至2℃以下、925 h Pa温度降至-1℃以下时,才会出现降雪。

Using conventional observation data and the wind profile radar data, an extreme spring blizzard process was analyzed in Shandong Province on Apr. 19, 2013. The results showed that the process is an obvious backflow situation. First of all, low-level eohl pad has formed, and climbing of the high-level of moist air in the cooling mat is the favorable circulation background of the process. 850 hPa quasi static vertical shear is a key system, its history is nearly nine hours. When the height of the vertical shear is 1. 5 km, up and down wind direction is the northwest wind and south wind, precipitation properties is rain or sleet. When the height of vertical shear down to the height of 1.2 km suddenly, up and down the wind direction change into the northwest and east wind, precipitation properties is pure snow. After shear line disappears, the meso- andmicro-scalesystems under 600 m plays a triggering role. Precipitation properties is snow when temperature of surface and 1 000 hPa is below 2 ℃and below 1 ℃ of 925 hPa in the process.