적도태평양에서 dipole구조를 가지는 해수면 온도 변동성의 특성

Abstract

An index is defined to describe changes in ENSO amplitude without any filtering of the raw sea surface temperature (SST) data in the observations and a long-term simulation of a coupled general circulation model (CGCM). Using this simple index we examine the relationship between changes in ENSO amplitude and the variability of dipole-like SST mode in the tropical Pacific. Our analysis shows that the dipole-like characteristics of this mode is due to a difference of an east-west zonal displacement of El Nino and La Nina’s center of action between periods of relatively high and low ENSO variance. The El Nino’s center is shifted eastward compared to that of La Nina during periods of high ENSO variance, whereas during periods of low ENSO variance this east-west zonal displacement for the El Nino and La Nina is reversed. We argue here that this dipole pattern is the non-linear rectification of periods of high and low ENSO variance, and is not the cause for the changes in the variance.