热带MJO对2009年11月我国东部大范围雨雪天气的可能影响  

POSSIBLE IMPACTS OF THE MJO ON THE SEVERE ICE-SNOW WEATHER IN NOVEMBER OF 2009 IN CHINA

作　　者：贾小龙[1] 梁潇云[1] 

机构地区：[1]国家气候中心/中国气象局气候研究开放试验室,北京100081

出　　处：《热带气象学报》2011年第5期639-648,共10页Journal of Tropical Meteorology

基　　金：国家自然科学基金(40905035;40805027);973项目(2010CB428606);公益性行业科研专项(GYHY200806004);科技部科技支撑项目(2007BAC29B04;2009BAC51B05)共同资助

摘　　要：结合对历史资料的分析,研究了2009年11月热带地区一次强的热带大气季节内振荡(MJO)过程与11月我国东部大范围雨雪天气的可能联系,结果表明2009年11月强的MJO过程是我国东部大范围雨雪天气的一个重要的影响因子。MJO对流11月上中旬在印度洋地区异常活跃,尤其是MJO对流中心在第3位相(印度洋中东部)维持了9天(7—16日),对应了11月两次最强的降水(雪)过程。对MJO历史事件的合成分析显示,当MJO对流位于印度洋时,我国东部大部地区降水概率明显增加,温度偏低,与2009年11月的实况一致。中高纬地区大气环流的异常有可能受到热带MJO对流强迫的影响,这种影响可能通过遥相关的方式来实现。当MJO对流位于印度洋时,有利于欧亚中高纬环流维持两脊一槽的分布,同时西太平洋副热带高压偏强偏西,东亚东部地区维持一条显著的对流活跃带,这些环流异常形势与2009年11月的实况也较一致,体现了MJO对热带外地区环流异常影响的一般特征。热带地区MJO对流的异常通过对流加热强迫,除引起大尺度纬向环流异常外,同样会引起经向环流异常,从而影响热带外地区环流。当MJO对流位于印度洋时,西太平洋地区为异常的下沉运动控制,东亚东部辐合上升,在热带和中纬度地区之间形成一个异常的经向环流圈,经向环流的存在进一步有利于低层低纬度水汽的向北输送,造成东部降水偏多。利用MJO的发展和演变,对于把握类似2009年11月这样的大范围雨雪气候异常很有帮助。Possible relationships between the MJO and a severe ice-snow weather process in November of 2009 in Eastern China were analyzed.Results showed that a strong MJO process was one of the strong impact factors.MJO convection was markedly active over the Indian Ocean,especially with the convection center maintaining nine days in phase 3 of MJO（the middle-east Indian Ocean） and just corresponding to two strongest ice-snow processes.Composites of MJO events showed that when the MJO convective center is located over the Indian Ocean,rainfall probability is significantly enhanced and the temperature is lower than normal in eastern China,which is consistent with the situation in November of 2009.Atmosphere circulation anomalies of mid-high latitude can be influenced by the tropical MJO convection forcing and this influence could be realized by tele-connection.When the MJO is over the Indian Ocean,it is favorable for the maintenance of the two ridge-one trough circulation situation at mid-high latitudes;meanwhile,the western Pacific subtropical high is stronger and more westward than normal,and an evident convective belt appears over eastern East Asia.All these circulation anomalies shown in the composite results also appeared in November of 2009,which indicates the general features of relationships between the MJO and the circulation anomalies over the extratropics.Besides the zonal circulation anomalies,the MJO convective can also lead to meridional circulation anomalies.When the MJO is over Indian Ocean,the western Pacific region is dominated by anomalously downward motion,and the eastern East Asia is controlled by convergence and upward motion.Therefore,an anomalous meriadinal circulation is formed between the tropics and middle latitudes,which further enhances the northward transportation of low-level moisture.It is potentially helpful to understand and even forecast,using MJO,such kind of ice-snow weather anomalies as in November 2009.

关 键 词：MJO 雨雪天气 印度洋 热带 中高纬 

分 类 号：P423.35[天文地球—大气科学及气象学]