一次秋季沙尘暴的诊断和天气雷达观测分析

 使用NCEP 1°×1°每天4次的再分析资料对2006年10月5日发生在甘肃、内蒙古西部、蒙古国南部沙尘暴天气的位势涡度、干侵入、局地垂直螺旋度进行了诊断分析。分析结果表明：对流层高层的高位势涡度库位势涡度柱向下、向南伸展,在等熵面陡立处,垂直涡度分量急剧增大,使锋面低压迅速发展,低空急流形成;高空干冷空气向东南下侵,蒙古国南部从西到东的大风、沙尘暴由下滑冷锋引起,持续时间长,强度强;河西走廊、内蒙古西部的大风、沙尘暴由上滑冷锋引起,持续时间短,强度相对弱。利用张掖CINRAD-CC天气雷达观测数据对导致张掖沙尘暴的β中尺度双阵风锋结构进行了初步分析,认为第二条阵风锋使风速忽然加大,阵风锋的辐合上升使沙尘扬起抬升,能见度讯速下降。

Diagnostic Analysis and Weather Radar Observation of a Sand-dust Storm in Autumn

Based on the reanalysis data of NCEP 1°×1°, the diagnostic analysis on potential vorticity, dry intrusion and vertical helicity of a sand-dust storm process occurred in the west of Gansu and Inner Mongolia and the south of Mongolia during period from Oct.5, 2006 to Oct.6, 2006 was conducted. The high potential vorticity air from upper level of troposphere extended downwards and southwards, its vertical component increased rapidly at steep of iso-entropy plane, promoting the rapid development of the cyclone and resulting in a low level jet; at the same time, the upper level dry air intruded southeastwards, leading to the intensive and long-lasting gale and sand-dust storm from west to east in the south of Mongolia. Whereas, the gale and sand-dust storm occurred in Hexi corridor and west of Inner Mongolia are resulted from sliding upwards cold-front, lasting short period and behaving relatively weak intensity. There is certain corresponding relation between the evolution of the vertical helicity and the occurrence of sand-dust storm. The vertical distribution of helicity over the sand-dust storm area is the negative value in the upper levels and the positive value in the low levels. The centre of intensive sand-dust storm is just down the maximum value of helicity. In addition, making use of the observational data by CINRAD-CC weather radar we have analyzed the β-medium scale double gust-front structure that resulted in sand-dust storm in Zhangye of Gansu. It was concluded that the genesis of the dust-storm in study region is generated form the second gust-front.