一个新的ENSO监测指标的研究

A NEW INDEX FOR ENSO MONITORING

利用１９８２～１９９６年逐月平均ＳＳＴ和ＯＬＲ资料，首先通过奇异值分解（ＳＶＤ）技术研究了热带太平洋大气对流活动和海温场的时间和空间结构及其相互关系．结果表明，第一模态都明显地反映出ＥＮＳＯ信息，两场间具有很高的相关．分析了８０年代以来的ＥｌＮｉｎｏ／ＬａＮｉｎａ盛期的热带太平洋对流活动场以及ＮＩＮＯ３指数与ＯＬＲ场的点相关，结果指出，中东太平洋和西太平洋上存在类似偶极子型的两个符号相反的相关区，与ＳＶＤ第一模态空间分布型十分相似．由此建立了反映ＥＮＳＯ期间热带中东太平洋和西太平洋反向变化的对流涛动指数ＣＯＩ（ＣｏｎｖｅｃｔｉｖｅａｃｔｉｖｉｔｉｅｓＯｓｃｉｌａｔｉｏｎＩｎｄｅｘ）．进一步分析表明，ＣＯＩ对于ＥＮＳＯ过程的反映较为灵敏，它与ＮＩＮＯ３区指数的相关高于与南方涛动指数、ＮＣＥＰ使用的ＯＬＲ指数、太平洋信风指数等，它为今后ＥＮＳＯ监测提供了新的指标．

Based on monthly mean SST and OLR data during 1982～1996 and by applying Singular Value Decomposition (SVD)technique and correlation analysis, a new index for ENSO monitoring system is studied. The results show that tropical Pacific SST and OLR fields are significantly correlated. The first modes of these two fields derived from SVD clearly indicate ENSO signals. According to the analyses of the structure of OLR anomaly fields in the mature phases of both El Nio and La Nia, and the spatial correlation between NINO 3 index and the tropical Pacific OLR field, this paper reveals that the pattern of the opposite centers like dipole over the tropical Pacific in OLR field is quite similar to the structure over the equatorial Pacific for the first modes of both OLR and SST. A Convective activities Oscillation Index (COI) is thus derived for the opposite variation structure of OLR between the eastern central Pacific and the western Pacific. Further analyses have confirmed that COI is a sensitive index to reflect ENSO signal. The correlation between COI and NINO 3 index is higher than the other indices (including SOI) used in operational ENSO monitoring system worldwide.