滇东北一次暴雪天气过程个例分析

Analysis of a heavy snow event in the Northeast of Yunnan Province

利用常规观测资料和多普勒雷达回波资料,综合分析了2008年1月31日发生在滇东北的一次暴雪天气过程.结果表明:过程前期500 hPa南支槽加深东移,槽前西南急流把孟加拉湾的水汽源源不断地向高纬度输送,为暴雪区提供了充足的水汽条件.阻高崩溃横槽转竖引导槽后冷空气南下,准静止锋补充加强,叠加在低层西南暖湿气流上空,触发了不稳定能量的释放.Ω型能量系统的建立和维持为强降雪的发生提供了足够的能量条件,强降雪发生在下游低能舌内.径向速度图上低层零速度带在0.38 km高度间隔内出现180°的顺转说明对流层低层存在强暖切变.西南方和东北方大片速度模糊区的出现反映了强西南急流的存在,西南急流的建立、维持和减弱时间与降雪强度的变化有较好的对应关系.强暖平流的存在和对流层低层1.0~1.2 km高度强垂直风切变的长时间维持为强降雪的产生提供了充足的动力条件.

Based on conventional data and Doppler radar echo,a heavy snow happened in the northeast of Yunnan Province on 31 January 2008 was analyzed.The result showed that the southern branch trough brought enough moisture and the cold front triggered the release of unstable energy.The establishment of "Ω" type energy system provided adequate energy for heavy snowfall.Zero velocity line in low troposphere veer 180° in 0.38 kilometer height interval demonstrated strong vertical wind shear in radial velocity field.Vel...