甘肃中部强沙尘暴成因分析

Analysis on Cause of Strong Sandstorm Occurring in Middle Gansu Province

利用1970—2006年甘肃中部13个县(市)的21例沙尘暴天气过程的各时次高空和地面资料,通过分析沙尘暴过程的影响系统,来研究甘肃中部近年来强沙尘暴天气频繁入侵的成因及特点。结果表明:甘肃武威东南部发生沙尘暴天气时,500hPa高空出现一支风速≥20m.s-1西北向的急流轴;河西走廊地形的"狭管效应"作用,使沙尘暴移速增快,强度增强,沙尘在翻越乌鞘岭后,相继侵袭白银、兰州、临夏等广大地区;进入21世纪以来,甘肃中部沙尘暴和强沙尘暴次数逐年增多,强度增强、影响范围扩大。

This paper researched the characteristics and causes of strong sandstorms invading the middle area of Gansu through analyzing the weather system by using the high and surface data from 1970 to 2006. The results show that a 500 hPa air jet （≥20 m. s^-1 ） came forth when sandstorm occurred in the southeast of Wuwei city of Gansu. The sandstorm speeded up and became more intense in effect of Hexi Corridor topog-raphy. Sandstorm climbed across the Wushaoling Mountain, then swept large extent of Baiyin, Lanzhou and Linxia etc. Entering the 21^st Century, the frequency of sandstorm and strong sandstorm increases, the intensity strengthens and the influencing region widens.