Japan Geoscience Union Meeting 2015

Presentation information

Oral

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

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

Tue. May 26, 2015 4:15 PM - 6:00 PM 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:Motoki Nagura(Japan Agency for Marine-Earth Science and Technology), Yukiko Imada(Meteorological Research Institute, Japan Meteorological Agency)

4:55 PM - 5:10 PM

[ACG32-09] Wintertime meridional teleconnection associated with convective activity over the tropical Northwestern Pacific

*Shion SEKIZAWA1, Yu KOSAKA1, Hisashi NAKAMURA1, Kazuaki NISHII1, Takahumi MIYASAKA1 (1.Research Center for Advanced Science and Technology, University of Tokyo)

Tropical climate variability and associated meridional teleconnections are major origins of seasonal predictability. Statistically, it has been known that El Nino (La Nina) brings warmer (colder) winter to Japan, providing a basis for winter seasonal predictions. However, few studies examined structure and mechanisms for that tropical-extratropical teleconnection. In this study, we investigate the remote influence of wintertime convective activity over the tropical Northwestern Pacific on the atmospheric circulation in the extratropical Northern Hemisphere, by analyzing monthly observational data sets and an ensemble AMIP experiment for 1979-2012.
Convective activity over the tropical Northwestern Pacific is significantly correlated with El Nino-Southern Oscillation (ENSO), and our regression analysis shows that enhanced (suppressed) convection around the Philippines is associated with cold (warm) winter around Japan, which is consistent with the empirical relationship of ENSO. However, ENSO explains only half of the variance of the total convective activity around the Philippines, suggestive of a large contribution from atmospheric internal variability. We isolate the latter component by subtracting linear regression against an ENSO index from the observed anomalies and as inter-member variability in the ensemble AMIP experiment. Circulation anomaly patterns differ considerably between the ENSO-forced and internal components both in the observations and model, and the internal variability is more influential on the wintertime East Asian weather. Our analysis thus suggests that the atmospheric internal variability around the Philippines significantly limits the wintertime seasonal predictability in East Asia that arises from ENSO.