黄河内蒙古河段凌汛期寒潮特征及天气分型

Characteristic Analysis and Circulation Classification of Cold Waves During the Ice⁃Flood Season in Inner Mongolia Reach of the Yellow River

基于黄河内蒙古河段逐日气温资料、NCEP/NCAR逐日再分析资料和逐月海冰密度指数资料等,统计分析了近10 a内蒙古河段凌汛期寒潮过程的基本气候特征、冷空气移动路径以及环流分型特征,并进一步探讨了寒潮变化的可能原因,结果表明:(1)近10 a内蒙古河段凌汛期共出现98次寒潮过程,过程持续时间1~5 d不等,平均为2.1 d,其中1~2 d的过程较多,累计次数占总次数的73%。(2)寒潮过程呈显著增多趋势,增加速率为1.4次/a,近5 a平均次数较2010—2014年增加127%。(3)按照冷空气移动路径,将寒潮天气过程划分为偏北路冷空气型、偏西路冷空气型、偏东路冷空气型以及偏北路与偏东路共同影响型4类,其中偏北路冷空气型最为常见,占寒潮过程总数的70%以上,其他3类占比均不到10%。(4)西伯利亚高压强度增强是造成近5 a寒潮次数增加的关键大气环流因素,而北极海冰密度减小是造成寒潮次数增加的重要外强迫因素。

Based on the daily air temperature data,daily NCEP/NCAR reanalysis dataset and monthly sea ice density index data,the climate characteristics,cold air moving paths and circulation typing characteristics of the cold waves during the ice⁃flood season in Inner Mongolia reach in recent 10 years were statistically analyzed,and the possible factors causing the variation of the cold wave frequency were further dis⁃cussed.The results show that a)in recent 10 years,there are 98 times cold wave processes in Inner Mongolia during the ice⁃flood season.The processes last about 1 to 5 days with an average of 2.1 days,and the most common processes are that last 1 to 2 days accounting for 73%of the total.b)The cold wave frequency in Inner Mongolia reach during the ice⁃flood season show a significant increase rate of 1.4/a and the av⁃erage frequency during 2015-2019 is 127%more than that during 2010-2014.c)According to the moving paths of cold air,the cold wave processes are classified into 4 types of north road cold air,west road cold air,east road cold air and north⁃east road cold air.The type with the north road cold air is the most common accounting for more than 70%of the total,while the other three types respectively accounted for less than 10%.d)The intensification of the Siberian high is the key atmospheric circulation factor that causes the increase of cold wave frequency in recent 5 years,while the decrease of arctic sea ice density is the important external forcing factor.