Abstract: Using the satellite sea surface temperature (SST) from 1991 to 2015 over the equatorial Pacific Ocean, the variation of tropical instability waves (TIWs) and its relationship to El Niño-Southern Oscillation (ENSO) were investigated. The activity of TIWs was measured by the root-mean-square value of the 20~50 day band-pass-filtered SST perturbations. Remarkable TIWs were found in the Niño3 area (150°W-90°W, 5°S-5°N), where the mean TIW activity was approximately 0.20°C, with its maximum exceeding 0.35 ℃ between the equator and 3°N. In addition, the TIW activity was weaker south of the equator, in which its strength reached 0.2 only in the winters of 1998, 2007 and 2010 when La Niña events occurred. The pattern that the TIWs were more active during La Niña and less active during El Niño events was confirmed. Meanwhile, we found that the TIW activity, while in phase with the strength of the surface zonal current shear and the cold tongue front, led the ENSO amplitude about 2~3 months due to its more rapid response than the Niño3 SST to dynamic and thermal processes in the equatorial Pacific associated with ENSO. This implies that the phase and activity of ENSO can be predicated by the TIW activity a few months earlier from satellite SST observations.

Key words: tropical instability waves, El Niño-Southern Oscillation, satellite sea surface temperature, intraseasonal, equatorial Pacific