The dominant annual cycle of sea surface temperature(SST)in the tropical Pacific exhibits an antisymmetric mode,which explains 83.4％total variance,and serves as a background of El Nino-Southern Oscillation(ENSO).However,there is no consensus yet on its anomalous impacts on the phase and amplitude of ENSO.Based on data during 1982-2022,results show that anomalies of the antisymmetric mode can affect the evolution of ENSO on the interannual scale via Bjerknes feedback,in which the positive(negative)phase of the antisymmetric mode can strengthen El Nino(La Nina)in boreal winter via an earlier(delayed)seasonal cycle transition and larger(smaller)annual mean.The magnitude of the SST anomalies in the equatorial eastern Pacific can reach more than±0.3° C,regulated by the changes in the antisymmetric mode based on random sensitivity analysis.Results reveal the spatial pattern of the annual cycle associated with the seasonal phase-locking of ENSO evolution and provide new insight into the impact of the annual cycle of background SST on ENSO,which possibly carries important implications for forecasting ENSO.
Annual cycleSST anomalyAntisymmetric modeENSO
Song Jiang、Congwen Zhu、Ning Jiang
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State Key Laboratory of Severe Weather(LASW),Chinese Academy of Meteorological Sciences,Beijing,China
College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing,China
国家科技期刊平台
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