Japan Geoscience Union Meeting 2014

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Oral

Symbol A (Atmospheric, Ocean, and Environmental Sciences) » A-CG Complex & General

[A-CG37_28PM2] Multi-scale ocean-atmosphere interaction in the tropics

Mon. Apr 28, 2014 4:15 PM - 5:59 PM 423 (4F)

Convener:*Motoki Nagura(Japan Agency for Marine-Earth Science and Technology), Takuya Hasegawa(Japan Agency for Marine-Earth Science and Technology), Ayako Seiki(Japan Agency for Marine-Earth Science and Technology), Tomoki Tozuka(Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo), Hiroki Tokinaga(International Pacific Research Center, University of Hawaii), Masamichi Ohba(Central Research Institute of Electric Power Industry (CRIEPI), Environmental Science Research Laboratory), Yukiko Imada(Atmosphere and Ocean Research Institute, the University of Tokyo), Chair:Tomoki Tozuka(Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo), Masamichi Ohba(Central Research Institute of Electric Power Industry (CRIEPI), Environmental Science Research Laboratory)

4:50 PM - 5:05 PM

[ACG37-15] Important factors for long-term change in ENSO transitivity

*Masamichi OHBA1 (1.CRIEPI)

Keywords:Sea surface temperature, Pacific Ocean, El Nino/Southern Oscillation, Indian Ocean

El Nino and La Nina exhibit significant asymmetry in their duration. El Nino tends to turn rapidly into La Nina after the mature, while La Nina tends to persist for up to 2 years. Reconstructed historical sea surface temperatures (SST) show a significantly increase in the intensity of El Nino-Southern Oscillation (ENSO) asymmetry, particularly El Nino transitivity, during the last six decades. Atmospheric observational data have shown that the relationship between El Nino and surface zonal wind anomalies over the equatorial Western Pacific (WP) has strengthened, and anomalous WP easterlies have appeared after the 1970s climate regime shift. To investigate the dependency of ENSO transitivity on its amplitude, a suite of idealized experiments using an atmospheric general circulation model (AGCM) is performed by imposing historical SST and 12 different ENSO-related SST anomalies exhibiting equal spatiotemporal distribution but different amplitude. Our AGCM experiments show strong nonlinearity in the WP zonal wind against the amplitude of the warm phase.