2014年春季内蒙古2次大风降雪寒潮过程分析

对于环流特征相似的寒潮过程，其爆发的方式、产生的天气和影响的区域基本相似，但个别寒潮过程却存在较大的差异，造成预报上的误判。针对此类特例，基于常规气象观测资料，自动站观测资料和NCEP逐6 h 1°×1°再分析资料，应用天气学分析和诊断方法，对2014年4月24日（过程1）和5月1日（过程2）2次寒潮天气过程的环流、系统和爆发的动力、热力学机制等进行对比分析。结果表明：2次过程北半球中高纬500 hPa环流形势均具有两脊一槽的环流特征。寒潮区域升温明显，前期平均温度分别比历史同期偏高1.0~7.3℃和0.1~10.7℃，500 hPa冷槽和强锋区均在新疆北部堆积、爆发南侵；2次过程在爆发方式和成因上存在着较大的差异，过程1中促使寒潮爆发流场为横槽转竖，槽前疏散结构和正涡度平流使低槽切断出低涡并东南移，冷平流中心移至槽前，横槽转竖寒潮爆发。过程2为低槽东移，冷槽移过阿尔泰山和蒙古高原加深东移，冷空气入侵内蒙古，寒潮爆发。虽然2次过程均造成了全区范围的强降温，但由于上述影响方式和成因的不同，使得大风、沙尘暴和降水呈现出不同的影响特点。寒潮过程中大风和沙尘暴的分布除与冷平流有关外，还与高空动量下传的地点和时间密切相关，对于寒潮过程中的降水而言，低层的温度层结及其水汽输送特点，决定了不同地区的相态变化和降水的量级。通过关注环流相似寒潮过程中的爆发方式和动力过程，对于正确预报寒潮天气造成的不同地区的降温、大风、沙尘和降水具有很好的借鉴意义。

Analysis of Two Cold Wave Processes with Gale and Snow in Inner Mongolia in the Spring 2014

The cold wave process with similar circulation characteristics have similar outburst pattern, climate and range of influence, but there are also unique characteristics for individual cold wave process and the difference can result in the wrong judgment in forecast. In this special case, based on routine observation, automatic meteorological observing station and NCEP 1°×1° 6 h interval reanalyzed data, two cold waves occurred in April 24 (process 1) and May 1 (process 2) in 2014 in Inner Mongolia were comparatively analyzed on circulation situation, system, thermodynamic and the dynamic mechanism of the cold wave outburst, utilizing synoptic and diagnostic analyses method. The results are as follows: in middle and high altitudes of northern hemisphere, the circulation patterns of the two cold waves showed ‘one trough and tow ridge’ at 500 hPa. Based on the temperature rising strongly in prior period of the two cold waves, the average temperatures were 1.0-7.3 and 0.1-10.7℃ higher than the same period. The cold trough and strong frontal zone at 500 hPa were accumulated in the north of Xinjiang, and the cold wave broke out and invaded to the south. There were discrepancies between the burst and cause of the two cold waves: process 1 belonged to the revising of the transverse trough, and the trough was strengthened to vortex meanwhile moved to southeast because of evacuation structures and the positive vorticity advection before the trough, when the cold advection center moved to the front of the trough, transverse trough was revised and the cold wave broke out. Process 2 belonged to the small trough moving eastward, and the cold trough deepened after moving across the Altai Mountains and Mongolia plateau, finally the cold air invaded to Inner Mongolia and the cold wave broke out. Although strong cooling borough-wide was caused by the two cold waves, the gale, sandstorm and precipitation showed different characteristics because of the different influence ways and causes. The gale and sandstorm were correlated with not only the cold advection but also when and where the momentum disseminated. In terms of the precipitation of the two cold waves, the characteristics of water vapor transport and temperature stratification in the low layer were favorable to precipitation and precipitation transformation. Focusing on the burst and dynamic process of the similar cold waves was good for the forecasting of cooling, gale, sandstorm and precipitation.