Fu, C., H. F. Diaz, and J. O. Fletcher, 1987: Characteristics of the response of sea surface temperature in the Central Pacific associated with El Niño/Southern Oscillation. In The Climate of China and Global Climate, D. Ye, C. Fu, J. Chao, and M. Yoshino (Eds.), China Ocean Press and Springer-Verlag, 177-201.


The zonal distribution of sea surface temperature (SST) in the equatorial Pacific (4°N - 4°S, 120°E - 80°W) associated with ENSO has been studied by using the seasonal mean file of the Comprehensive Ocean-Atmosphere Data Set (COADS) for the period 1928-1983.

The warmest area in the western-central Pacific shows very little annual variation, but is very sensitive to the ENSO, displaying large variability during such episodes. The eastward migration of this warmest area (28.5°C isotherm is used here as criterion related to the strong tropical convection and heavy rainfall) is a common feature in the developing stage of almost all ENSO events since 1928, not only for the event of 1982. The extent of its eastward migration varies from event to event, and represents a large contribution to the interannual variability of zonal SST distribution in the equatorial Pacific, comparable to the behavior of the equatorial cold tongue in the east. This warmest water is not a passive factor, but an active one in the development of ENSO.

Eigenvector analysis of zonal profiles of SST in this area shows three major patterns. Pattern A is warm in the east and central areas with slightly below normal in the west (1972 type ENSO). Pattern B is warm in the east with normal in the central and slightly below normal in the west (1976 type ENSO) and Pattern C is nearly uniformly warm in the entire area (1963 type ENSO). These three patterns account for 62% of the total seasonal equatorial Pacific SST variance about the mean ENSO profile. The patterns of SST profile mainly depend on the relative contribution of the warmest water in the west-central Pacific and the equatorial cold tongue in the east. The west-to-east SST gradient in these three patterns is appreciably different, which cold prove useful in distinguishing the types of ENSO in the future.