2008年初持续性低温雨雪冰冻事件的东亚高空急流特征  

THE CHARACTERISTICS OF EAST ASIAN JET STREAM IN SEVERE SNOW STORM AND FREEZING RAIN PROCESSES OVER SOUTHERN CHINA IN EARLY 2008

作　　者：张春艳[1] 张耀存[1] 

机构地区：[1]南京大学大气科学学院,江苏南京210093

出　　处：《热带气象学报》2013年第2期306-314,共9页Journal of Tropical Meteorology

基　　金：国家自然科学基金项目(41130963);公益性(气象)行业专项经费(GYHY201006019);博士点基金共同资助

摘　　要：利用NCEP/NCAR逐日再分析资料和MICAPS系统提供的高空客观分析资料,对2008年初发生在中国南方地区的4次持续性低温雨雪冰冻过程期间,东亚高空副热带急流和温带急流的时空变化特征进行分析,发现副热带急流总体强度偏强、位置偏北。副热带急流的北界越北即南北跨度越大,雨雪冰冻过程持续时间越长;副热带急流中心强度越强,雨雪冰冻天气强度越大、范围越广。副热带急流的经向风分量异常偏强区域与雨雪冰冻强度较大区域一致。同时,温带急流的纬向西风和经向北风明显偏强,其强度的强、弱变化与强降雪过程的开始、增强、结束时间密切相关。其经向分量异常区域以北风为主,即当温带急流的经向北风分量和副热带急流的经向南风分量都较强时,对应的雨雪冰冻天气过程较强。对低温雨雪过程的前期环流分析表明,副热带急流和温带急流的全风速及纬向分量在该事件发生前半个月就开始有明显的前兆,两支急流的经向分量在该事件发生前20天开始有前兆信号,且副热带急流的经向分量、温带急流纬向分量的迅速减弱对该事件的结束有明显的指示意义。Based on the National Centers for Environmental Prediction and National Center for Atmospheric Research （NCEP/NCAR） daily reanalysis datasets and the upper air grid data provided by MICAPS, the characteristics of the spatial-temporal variations of the East Asian jet stream （EAJS） in the severe snow storm and freezing rain processes over Southern China in January 2008 are investigated. During this period, every severe snow storm weather process was closely linked to the extraordinarily abnormal variations of East Asian subtropical jet （EASJ） and East Asian polar-front jet （EAPJ）. The stronger EASJ with abnormally northern position of the jet axis led to storms that are more intense, more extensive and endure longer time. The most severe storm occurred in the area with long-time persistent southerly wind of EASJ. In the meantime, EAPJ was more significantly enhanced, accompanied by the strengthened westerlies and the prevailing of the northerlies. Variations of their strength are closely related to the start, enhancement, and the end of the heavy snowfall. It means that the abnormal northerlies of EAPJ and the southerlies of EASJ reinforce the snowstorms. Further analysis indicates that full wind speed belt and the westerly wind of the two jet streams exhibit predictive signs about half a month prior to the event while the meridional component of the two jet streams show precursory signals about twenty days before the event, and the rapid weakening of the meridional wind of EASJ and the westerly wind speed of EAPJ signifies the ending of the event, which are of great encouragement for the short-term climate forecasting of the meteorological disasters in the future.

关 键 词：低温雨雪冰冻 温带急流 副热带急流 前兆信号 

分 类 号：P423.3[天文地球—大气科学及气象学]