日本地球惑星科学連合2018年大会

講演情報

[EE] ポスター発表

セッション記号 A (大気水圏科学) » A-OS 海洋科学・海洋環境

[A-OS08] 季節から十年規模の気候変動と予測可能性

2018年5月20日(日) 10:45 〜 12:15 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:望月 崇(国立研究開発法人海洋研究開発機構)、V Ramaswamy(NOAA GFDL)、森岡 優志(海洋研究開発機構)

[AOS08-P02] Mid-latitude source of the ENSO-spread in SINTEX-F ensemble predictions

*尾形 友道1土井 威志1森岡 優志1Behera Swadhin1 (1.海洋研究開発機構 アプリケーションラボ)

キーワード:ENSO、季節予測、スプレッド

The ensemble spread of seasonal prediction is investigated in this study to understand its role in the predictability of El Nino/Southern Oscillation (ENSO) based on the results of SINTEX-F2, a coupled ocean-atmosphere general circulation model. In SINTEX-F2 seasonal prediction system, first precursor based on the ENSO spread appears as a cyclonic wind anomaly over the central north Pacific in boreal winter (January). Then, warm-SST, positive-rainfall and cross-equatorial southerly wind anomalies appear over the northern hemisphere during the following spring (particularly in April). Such anomalies in April also accompany westerly wind anomaly in the western equatorial Pacific. Finally, El Nino-like conditions with warmer-SST and higher-rainfall become dominant in inter-member deviation after boreal summer.
500 hPa geopotential height suggests that stochastic atmospheric precursor (without oceanic signal) during winter causes El Nino-like spread through air-sea interaction. The oceanic response in the form of upper heat content (in the top 150m) appears as a result of equatorial wind forcing during boreal spring and summer. These results of seasonal precursor signals in SINTEX-F2 ENSO spread suggest that the seasonal footprinting mechanism (SFM) type air-sea coupling process is important for ENSO spread related to the “spring-barrier”. The state dependence of ENSO spread to background ensemble-mean state (particularly sensitivity of the SFM and California Nino in “post El Nino” phase) was also discussed.