构建描述两种ENSO类型的新指数  

Construction of new indices for the two types of ENSO events

作　　者：秦坚肇 王亚非[1] 

机构地区：[1]中国气象科学研究院灾害天气国家重点实验室,北京100081

出　　处：《气象学报》2014年第3期526-541,共16页Acta Meteorologica Sinica

基　　金：国家重点基础研究发展计划973项目(2012CB417202);国家自然科学基金项目(41375091);灾害天气国家重点实验室基本科研业务费

摘　　要：利用英国气象局哈得来中心的1950—2011年月平均海表温度资料,采用联合回归-经验正交函数分解方法得到东部太平洋型ENSO(东部型ENSO)和中部太平洋型ENSO0中部型ENSO)的热带太平洋海温分布特点,进而定义了计算相对简单的东部型ENSO指数(I_(EP))和中部型ENSO指数(I_(CP))来分别描述两类ENSO。研究结果表明:首先,构建的I_(EP)和I_(CP)的相关性很小,接近正交,而且I_(EP)和I_(CP)能够反映两类ENSO不一致的偏度和周期,因此,这对指数能够清楚地区分两类ENSO。其次,I_(EP)和I_(CP)这两个指数可以描述厄尔尼诺和拉尼娜事件成熟期主要海表温度异常区的位置。再次,应用I_(EP)和I_(CP)从随机事件概率统计的角度给出两类厄尔尼诺和拉尼娜事件较为严格的定义,以便实时有效地监测两类ENSO。最后,利用新指数对两类ENSO的特征进行研究发现,强厄尔尼诺事件一般属于东部型,而强拉尼娜事件则为中部型,并且中部型拉尼娜事件发生的前期是东部型厄尔尼诺,此外,ENSO的发生演变机制在1976/1977年前后发生了改变。Taking into account the different equatorial Pacific sea surface temperature （SST）patterns obtained from a combined EOF-regression analysis for the Eastern Pacific type of ENSO （EP-ENSO）and the Centre Pacific type of ENSO （CP-ENSO）, this study constructs IEP （EP-ENSO Index）and ICP （CP-ENSO Index）for the two types of ENSO.The analysis is performed for the period of 1950-2011 using the monthly mean Met Office Hadley Centre SST analyses data.Some conclusions are as follows.Firstly,the two indices are nearly orthogonal and the skewness coefficients for IEP and ICP are 1.56 and -0.43,re-spectively.In addition,EP-ENSO and CP-ENSO show different periods.The former has two dominant periods,one is near the 2 year band and the other is near the 4-8 year band.The latter has two significant powers around the 2-4 year and 12 year band from 1965 to 1995.Therefore,low correlation,different leading periodicity and skewness are all desirable properties for the above defined indices to separate the EP and CP type of ENSO.Secondly,IEP and ICP indices can describe the location of SST anomalies in the mature period of the two types of El Ni^no and La Ni^na events.Thirdly,from the perspective of probabili-ty and statistics of random events,two types of El Ni^no and La Ni^na events are more strictly defined by using this pair of new indices,which could be applied to monitoring the two types of ENSO effectively and in real-time.Finally,the two new indices can also depict characteristics of the equatorial Pacific SST zonal propagation and evolution during ENSO events,their running lagged correlations capture different ENSO phase propagations and ENSO regime changes associated with the climate shift in 1976/1977.It is also noticed that most strong El Nino events belong to the EP type,but most strong La Nina events are to the CP type,and CP type of La Nina events tend to occur after the EP type of El Nino events.

关 键 词：东部型ENSO 中部型ENSO 海表温度异常 气候态转变 

分 类 号：P461[天文地球—大气科学及气象学]