Elucidation for irregularity of El Nino events by using an innovative multi-connected inversion approach with the 4-dimensional variational atmosphere-ocean data assimilation system

2008 Fiscal Year Final Research Report

• Project/Area Number: 18340139
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Meteorology/Physical oceanography/Hydrology
• Research Institution: Kyoto University
• Principal Investigator: AWAJI Toshiyuki Kyoto University, 大学院・理学研究科, 教授 (40159512)
• Co-Investigator(Kenkyū-buntansha): ISHIKAWA Youichi 京都大学, 大学院・理学研究科, 助教 (70335298) ; KONDA Masanori 京都大学, 大学院・理学研究科, 助教 (10273434)
• Project Period (FY): 2006 – 2008
• Keywords: データ同化 / エルニーニョ / 予測 / 大気海洋フィードバック

Research Abstract

四次元変分法大気海洋結合データ同化の利点を最大限に活かした1990年代の再解析プロダクトならびに変動の要因を特定する上に有益な顕著現象の逆解析データを作成・併用して、太平洋熱帯域を対象に詳細解析を行った結果、再解析データの精度は通常のシミュレーション結果と比べ海面水温にして約2倍程度向上し、熱輸送量はENSO 現象に規定され顕著な経年変動を示すとともに、その変動はrecharge-discharge 理論に西風バースト効果を組み入れることにより、これまで未解明であった90 年代におけるエルニーニョ発生の多様性の一側面を説明できるという新知見を得た.具体的には、従来の理論では欠けていたoff-equator での赤道ロスビー波の西方伝播に伴う南北熱・水輸送の時間変動過程と西岸からの赤道ケルビン波の伝播による東向き熱・水輸送のinterplay を従前のリチャージ理論に組み入れれば、エルニーニョの振幅と周期が不規則になることを明らかにすることに成功し、関連論文は米国地球物理学連合のJ. Geophys. Res.から刊行されるやいなや、その週刊ダウンロード数は世界第4位であった.

Research Products

• [Journal Article] High-resolution synthetic monitoring by a 4-dimensional variational data assimilation system in the northwestern North Pacific (2009)
  • Author(s): Ishikawa, Y., T. Awaji, T. Toyoda, T. InK. Nishina, T. Nakayama and S. Shima
  • Journal Title: Journal of Marine System (in press)
• [Journal Article] Ocean initialization for seasonal forecasting (2009)
  • Author(s): Balmaseda, M., O. Alves, A. Arribas, T.Awaji, D. Beringher, N.Ferry, Y. Fujii,T. Lee, M.Reineker, T. Rosati and D.Stammer
  • Journal Title: Oceanography (in press)
• [Journal Article] Ocean state estimation for climate research (2009)
  • Author(s): Lee, T., T. Awaji, M. Balmaseda, E. Greiner, M. Martin, and D. Stammer
  • Journal Title: Oceanography (in press)
• [Journal Article] A possible rolefor unstable coupled waves affected byresonance between Kelvin waves andseasonal warming in the development ofthe strong 1997-1998 El Nino (2009)
  • Author(s): Toyoda, T., S. Masuda, N. Sugiura, T.Mochizuki, H. Igarashi, M. Kamachi, Y.Ishikawa, and T. Awaji
  • Journal Title: Deep-Sea Res. 1, 56 Pages: 495-512
• [Journal Article] Temporalevolution of the equatorial thermoclineassociated with the 1991-2006 ENSO (2009)
  • Author(s): Masuda, S., T. Awaji, T. Toyoda Y.Shikama, and Y. Ishikawa
  • Journal Title: J. Geophys.Res.114 C03015 Pages: doi : 10.1029
• [Journal Article] Possible oceanic feedback inextratropics in relation to the NorthAtlantic SST tripole, Geophys. Res (2009)
  • Author(s): Mochizuki, T., T. Awaji and N. Sugiura
  • Journal Title: 36, L05710 10 Pages: doi : 10.1029/2008GL036781
• [Journal Article] 海洋環境変動の把握技術と水産資源変動解析に果たす役割 (2009)
  • Author(s): 五十嵐弘道、淡路敏之、豊田隆寛、増田周平、杉浦望実、佐々木祐二、一井太郎、秋山秀樹、畠山清
  • Journal Title: 水産海洋研究 73(1) Pages: 34-35
• [Journal Article] Summertimeevolution of decadal sea surfacetemperature anomalies in themidlatitude North Pacific (2008)
  • Author(s): Mochizuki, T and T. Awaji
  • Journal Title: Journal of Climate 21 Pages: 1569-1588
• [Journal Article] Developmentof a four-dimensional variationalcoupled data assimilation system forenhanced analysis and prediction ofseasonal to interannual variations. (2008)
  • Author(s): Sugiura N., T. Awaji, S. Masuda, T.Mochizuki, T. Toyoda, T. Miyama, H. Igarashi and Y. Ishikawa
  • Journal Title: J.Geophys Res. 113, C10017 Pages: doi : 10.1029/2008JC004741
• [Journal Article] Structured sun glitterrecorded in an aster along-track stereoimage of Nam Co Lake(TIBET) : Aninterpretation based on supercriticalflow over a lake-floor depression (2008)
  • Author(s): J. P. Matthews, X. D. Yang, J. Shen and T. Awaji
  • Journal Title: J.Geophys.Res 113, C01019 Pages: doi : 10.1029/2007JC004204
• [Journal Article] ARegional Ocean-Atmosphere Model forEastern Pacific Climate (2007)
  • Author(s): Shang-Ping Xie, T. Miyama, Y. Wang, H.Xu, S. P. de Szoeke, R. J. Small, K.J.Richards, T. Mochizuki, and T. Awaji
  • Journal Title: TowardsReducing Tropical Biases, Journal ofClimate 20 Pages: 1504-1522
• [Journal Article] Asimple diagnostic calculation of marinestratocumulus cloud cover for use ingeneral circulation models (2007)
  • Author(s): Mochizuki, T., T.Miyama and T.Awaji
  • Journal Title: J.Geophys.Res. 112, D06113 Pages: doi : 1029/2006JD007223
• [Journal Article] Improved coupled GCM climatologies for summer monsoon onset studies over Southeast Asia (2007)
  • Author(s): Mochizuki, T., H.Igarashi, N.Sugiura, N.Ishida and T.Awaji
  • Journal Title: Geophys.Res. Lett. 34, L01706 Pages: doi : 10.1029/2006GL027861
• [Journal Article] Interannual variability of temperatureinversions in the subarctic NorthPacific (2006)
  • Author(s): Masuda, S., T. Awaji, N. Sugiura,T.Toyoda, Y.Ishikawa and K.Horiuchi
  • Journal Title: Geophys. Res. Lett. 33, L24610 Pages: doi : 10.1029/2006GL027865
• [Journal Article] Enhanced ventilation in theOkhotsk Sea through tidal mixing at theKuril Straits (2006)
  • Author(s): Nakamura T., T. Toyoda, Y. Ishikawa and T. Awaji
  • Journal Title: Deep Sea Res. 53 Pages: 425-448
• [Presentation] K7 OceanReanalysis Experiment by Using a 4D-VARData Assimilation System (2009)
  • Author(s): Awaji,T., Shuhei Masuda, Nozomi Sugiura,Takahiro Toyoda, Hiromichi Igarashi,Yoichi Ishikawa, Yuji Sasaki
  • Organizer: Internationalworkshop on the North Pacific Oceanobservation Strategy for carbon cycleand climate change
  • Place of Presentation: Tokyo
  • Year and Date: 20090302-04
• [Presentation] DEEP OCEANreanalysis experiment By using a4D-VAR adjoint method (2008)
  • Author(s): Masuda, S., T. Awaji , N. Sugiura, T.Toyoda, H. Igarashi, Y. Sasaki, T.Kawano, and M. Fukasawa
  • Organizer: Final GODAE symposium
  • Place of Presentation: Nice
  • Year and Date: 20081212-15
• [Presentation] Application of ocean reanalysis to the diagnosis of two pelagic squid stocks (2008)
  • Author(s): Igarashi, H. (JAMSTEC), T.Awaji (KyotoUniv., FRCGC), N.Sugiura (FRCGC), S.Masuda (FRCGC), T.Toyoda (FRCGC), Y.Sasaki (FRCGC), T.Ichii (NRIFSF/FRA), H. Akiyama (SNFRI/FRA), K.Hatakeyama(JAMSTEC)
  • Organizer: Final GODAE symposium
  • Place of Presentation: Nice
  • Year and Date: 20081212-15
• [Presentation] 赤道アフリカ東部における降水量の年々変動と水蒸気輸送について (2008)
  • Author(s): 五十嵐弘道・淡路敏之
  • Organizer: 日本気象学会2008 年度秋季大会
  • Place of Presentation: 仙台
  • Year and Date: 20081119-21
• [Presentation] assimilation experiment with a fully coupled GCM (2008)
  • Author(s): Sugiura, N., S.Masuda, T.Awaji, T.Toyoda, H.Igarashi, Y.Sasaki
  • Organizer: Asia Oceania Geophysical Society
  • Place of Presentation: Busan
  • Year and Date: 20080616-20
• [Presentation] Application of ocean dataassimilation to the diagnosis of neonflying squid and jumbo flying squidstock assessment (2008)
  • Author(s): Igarashi, H. (JAMSTEC), T.Awaji (KyotoUniv., FRCGC), N.Sugiura(FRCGC), T.Toyoda (FRCGC), Y.Sasaki (FRCGC), T.Ichii(NRIFSF/FRA), H.Akiyama(SNFRI/FRA), K.Hatakeyama(JAMSTEC)
  • Organizer: Asia Oceania Geophysical Society
  • Place of Presentation: Busan
  • Year and Date: 20080616-20
• [Presentation] Interannual variabilities ofeastern subtropical mode waters in theNorth and the South Pacific identifiedfrom reanalysis datasets obtained by4DVAR data assimilation (2008)
  • Author(s): Toyoda,T., S.Masuda, N.Sugiura,H.Igarashi, Y.Sasaki, Y.Ishikawa, T.Awaji
  • Organizer: Asia Oceania Geophysical Society
  • Place of Presentation: Busan
  • Year and Date: 20080612-20
• [Presentation] National Presentation Japan (2008)
  • Author(s): Kamachi, M and T. Awaji
  • Organizer: IGST-XIII-2008-GODAE(Silver Spring/Washington DC)
  • Place of Presentation: U.S.A
  • Year and Date: 20080601-05
• [Presentation] Four-dimensional variatinal coupled data assimilation (2007)
  • Author(s): Awaji.T
  • Organizer: AOGS 4th annual meeting
  • Place of Presentation: Bangkok
  • Year and Date: 2007-08-03