2010-2011年冬季La Ni(n)a事件对北半球极涡的影响分析

为了探讨强极涡与La Ni(n)a事件之间的关系,利用NCEP/NCAR(日平均、月平均位势高度及温度场)再分析资料对2010-2011年冬季进行个例研究.与气候态相比,2010-2011年冬季北半球平流层极涡偏强,同时,显著的强海温负异常(La Ni(n)a事件)也持续整个冬季.结果表明,受La Ni(n)a事件影响,对流层环流场和温度场得到较大的调整,出现PNA (Pacific North American)型异常环流形势和相对应的温度异常分布.2010年12月,阿留申地区出现负值的热量经向输送,使得该地区从对流层上升至平流层的行星波动与气候态相比明显减弱,从而导致平流层极涡较气候平均态偏强.这一La Ni(n)a事件对平流层极涡影响的动力过程也从1948-2010年期间选出的13个冬季强La Ni(n)a事件的合成分析结果中得到证实.

Winter 2010-2011: A Case Study of the Impact of La Ni(n)a on the Arctic Vortex

The relationship between strong arctic vortex and the La Ni(n)a events is found out by a case study of winter 2010-2011,using the NCEP/NCAR (daily and month mean) dataset.During the winter 2010-2011,the Arctic vortex was extremely stronger and persistent longer than normal,at the same time La Ni(n)a signals were surprisingly strong and long-lasting.The impact of La Ni(n)a on the polar vortex was investigated.Results show that the Pacific/North American (PNA) Pattern and corresponding temperature anomalies were forced by this La Ni(n)a event and the atmospheric circulation was greatly modified,too.Due to the negative heat flux in Aleutian region,the wave activities from the troposphere to the stratosphere were much weaker than their climatology.In addition,composite analyses also verified this La Ni(n)a's impact on Arctic Vortex,where 13 strongest La Ni(n)a cases during the period of 1948-2010 were selected.