2011年2月25—26日河套地区暴雪天气过程诊断分析

摘要

利用各种气象资料,对2011年2月25—26日发生在河套地区的暴雪天气过程进行诊断分析,结果表明：⑴500hPa中亚和东亚分别有冷槽活动,中亚槽前有分裂冷槽东移推动两槽间暖脊发展东移至河套以东,河套西部处在西南气流控制下。⑵当500hPa分裂东移的冷槽与700hPa高原槽和地面河套倒槽垂直叠置,高层有冷空气下沉锲入到地面倒槽后暖湿气层底部形成动力抬升时,触发暴雪产生。⑶700hPa负散度、正涡度,深厚的负垂直速度,高、低空急流垂直耦合形成的抽吸作用,高、低层冷暖平流造成的热力不稳定,较长时间水汽和热量输送、积聚,使高能、高湿舌伸入河套形成的位势不稳定,河套外围三面环山形成的地形阻挡抬升作用叠置在河套上空,为触发暴雪形成提供了强劲的抬升动力。%Using various meteorological data,the snowstorm weather processes was analyzed in Hetao Area from February 25,2011 to February 26,2011,The results showed that： F there was cold trough activity in Central Asia and South East Asia in 500hPa,in front of Central Asia,the split and eastward cold trough promoted the development of warm ridge between two trough to the east of Hetao area,and the west of Hetao area was under the control of southwest airflow.When the split and eastward cold trough in 500hpa superposed verticality with plateau trough in 700hPa and ground inverted trough in Hetao area,and the cold air sank to carve into the ground inverted trough which promoted the bottom of warm and wet air layer to upraise,the snowstorm formed.The negative divergence,positive vorticity in 700hPa,profound positive vertical speed,chimney effect which formed by vertical coupling of low-level jet stream,instable heating power which formed by low-level cold and warm advection,high energy and wet tongue entered into Hetao area and formed potential instability by transport and accumulation of moisture and heat for long time,terrain obstruct lifting effect which formed by surround of three mountains in Hetao superposed in the sky of Hetao area promoted powerful lifting effect for the formation of snowstorm.