A New Index for ENSO Monitoring

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 models 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 E1 and La , and the spatial correlation between NINO3 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 striation 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