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Feedback processes responsible for El Niño‐La Niña amplitude asymmetry
Author(s) -
Im SeulHee,
An SoonIl,
Kim Seon Tae,
Jin FeiFei
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl064853
Subject(s) - equator , asymmetry , wind stress , amplitude , shortwave , sea surface temperature , intensity (physics) , positive feedback , growth rate , atmospheric sciences , flux (metallurgy) , climatology , environmental science , physics , geology , materials science , optics , mathematics , geodesy , latitude , radiative transfer , geometry , electrical engineering , engineering , quantum mechanics , metallurgy
To analyze El Niño‐La Niña asymmetry, Bjerknes Stability Index analysis applied separately for El Niño and La Niña events. The growth rate of the El Niño is larger than that of the La Niña. Their difference is mainly due to an increased positive dynamical feedback. The enhanced sensitivity of the ocean's dynamic response to wind stress in El Niño is a primary cause for the increase in the positive dynamical feedbacks and is originated from the nonlinear response of atmospheric pattern to sea surface temperature (SST) anomalies, in particular the eastward shift of maximum wind loading and the equator‐confined wind patch during El Niño. The sensitivity of the wind intensity to SST anomalies is larger during El Niño; however, its impact is not greater than others. Difference in the negative feedbacks is mainly attributed to the damping by shortwave feedback, with the latent heat flux feedback being a secondary contributor.