Japan Geoscience Union Meeting 2015

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Symbol A (Atmospheric and Hydrospheric Sciences) » A-CG Complex & General

[A-CG32] Multi-scale ocean-atmosphere interaction in the tropics

Wed. May 27, 2015 9:00 AM - 10:45 AM 202 (2F)

Convener:*Hiroki Tokinaga(Disaster Prevention Research Institute/Hakubi Center, Kyoto Univesity), 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), Motoki Nagura(Japan Agency for Marine-Earth Science and Technology), 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), Ayako Seiki(Japan Agency for Marine-Earth Science and Technology), Takuya Hasegawa(Japan Agency for Marine-Earth Science and Technology)

9:15 AM - 9:30 AM

[ACG32-14] Impact of super tropical volcanic eruptions on ENSO

*Masamichi OHBA1, Hideo SHIOGAMA2, Tokuta YOKOHATA2, Masahiro WATANABE3 (1.Central Research Institute of Electric Power Industry (CRIEPI), 2.Center for Global Environmental Research, National Institute for Environmental Studies, 3.Atmosphere and Ocean Research Institute (AORI) The University of Tokyo)

Keywords:Super Volcanic Eruption, Sea surface temperature, Pacific Ocean, El Nino/Southern Oscillation

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.