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Lecturer: Chia-Ping Chiang Date : 2009/03/05

Vertical current structure and throughflow transport of the Kuroshio in the East China Sea, and south and east of Japan. Lecturer: Chia-Ping Chiang Date : 2009/03/05. Outlines. Introduction Literature Reviews Model Description and Validation Conclusion Future Work.

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Lecturer: Chia-Ping Chiang Date : 2009/03/05

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  1. Vertical current structure and throughflow transport of the Kuroshio in the East China Sea, and south and east of Japan Lecturer: Chia-Ping Chiang Date : 2009/03/05

  2. Outlines • Introduction • Literature Reviews • Model Description and Validation • Conclusion • Future Work

  3. Introduction ~ The Kuroshio • 為一主要的西部邊界流，不只影響東亞地區區域性的氣候系統，甚至影響全球海洋氣候變化。 • 起源自離開菲律賓沿岸朝北方向流動的支流，由台灣東部進入東海，沿著東海海域的大陸坡朝東北方向流動。(H. Nitani 1972) • 在穿越日本九州(Kyushu)南方的Tokara海峽之後，黑潮沿著日本南方的海岸岸邊流動，並發展出直行型(straight)與彎流型(meandering)的路徑。 • 由日本本州(Honshu)的房總半島(Boso Peninsula) 離開而進入深太平洋(deep Pacific Ocean)，此後被稱為黑潮延伸(the Kuroshio Extension)。 M. Andres et al. (2008) S. Itoh et al. (2008)

  4. Literature Reviews • M. Kawabe (1995):使用海表面高度的資料研究黑潮洋流路徑的變化，以及其與黑潮的流速、體積輸送以及黑潮之上游位置間的關係。 1963年至1975年間發生非大彎流路徑(non-large meander path)，1975年至1991年間主要發生大彎流路徑(larger meander path)。 體積輸送在發生NLM path較小，發生LM path較大。 • T. Kagimoto et al. (1997):使用高解析度的海洋環流模型(ocean general circulation model，OGCM) 研究日本南方黑潮季節性的體積輸送變化。 黑潮洋流通過PN-line的年平均體積輸送約為25 Sv。 • H. Ichikawa et al. (2000):使用1981年至1992年間每季一次的水文觀測與海水表層洋流等資料計算黑潮通過東海特定區域的體積輸送。 在夏季， WaterKuroshio Thermocline Water, Kuroshio Surface Water, Kuroshio Intermediate Water, and ECSShelf Water contribute to volume trapsport, 體積輸送最大可達28.5 Sv。

  5. Literature Reviews • H. Ichikawa et al. (2002):回顧並總結黃海與東海海域洋流系統的研究，指出由於測量表面洋流以及進行高解析度的三維數值環流模型的實驗，重大地改善人們對於此海域洋流系統的了解。 • M. Kashima et al. (2003):比較1993年至1995年期間日本四國島(Shikoku)南方黑潮主流及其回流區域各種深度下（700m、1500m、3000m）的水文觀測與直接洋流測量等資料。 對於中層海水(深度介於700m至1500m之間)與深層海水(深度介於1500m至3000m之間)，模式計算得到之地轉速度與觀測的結果相當接近。 • X. Guo et al. (2003) 使用三重嵌套海洋環流模型(triply nested OGCM) 檢驗在水平方向的解析度對於黑潮在東海(East China Sea)的流動情形與海平面高度變化的影響，並討論黑潮在日本九州島西南方(30°N、129°E)轉向的現象及季節性的南北向之位移。

  6. Literature Reviews • E. Oka et al. (2003):使用電導度—溫度—深度剖面儀(CTDP)與聲學都普勒海流剖面儀(ADCP)等資料，探討黑潮在日本九州島南方的洋流速度(current velocity)與位渦(potential vorticity)之垂直結構，並探討其與黑潮在日本南方區域路徑間的關係。 • H. Yoshinari et al. (2004):使用OGCM(MOM2.2, Modular Ocean Model Ver. 2.2)合併真實的地形資料(ETOPO5, Earth Topography -5 Minute)研究1960至2000年際間日本南方黑潮體積輸送的變化。採用兩種風數據集為模式的驅動力：(1)NCEP/NCAR 月平均的風場應力資料；(2)NECMWF 每日的風場資料； 兩種驅動力驅動下所得到的模式結果相近。 • M. Kawabe (2005):根據1990年代的觀測資料推論支配黑潮大灣流路徑(LM path)的發生條件。 當黑潮主軸採取曲率較小的北方位置通過Takara海峽時，在通過之後將採取LM的路徑。

  7. Literature Reviews Deep Current east of Japan • S. Fujio et al. (2000): 自1987年至1996年在日本東南方的伊豆-小笠原海溝(Izu-Ogasawara Trench)(34°N)的進行直接洋流測量，並皆於1995年在34°N與30°N進行水文觀測。 在海溝的兩側有流動方向相反的洋流，在西側為向南流動，在30°N與在34°N皆為5至8 Sv，在東側為向北流動的情形，由在30°N的5 Sv增加至在34°N的22 Sv。 • S. Fujio et al. (2005):使用直接洋流測量與水文觀測等資料研究日本東方的日本海溝(Japanese Trench)(38°N)的深海洋流。 在2000公尺深度以下，在海溝的兩側存在一對流動方向相反的洋流，在西側為向南流動，體積輸送為13.5 Sv，在東側為向北流動，體積輸送為5.5 Sv。 日本海溝東部的深海平原所測量到的洋流在38°N向西流動。

  8. Model Description • A 4th order, high resolution, and fully way-coupled duo-grid Pacific Ocean Model (DUPOM). • The control volume equations include the conservation of the fluxes of momentum (momentum balance), heat(energy balance), salt (material balance) across control volume faces.

  9. The TAI Domain • Grid resolution: 1/8°×1/8° • Longitude: 100~150°E • Latitude: 0~50°N Special Diagnositcs: • PN-Line (East China Sea, ECS) • TK-Line (Tokara Strait) • ASUKA-Line (South of Japan) • 34°N (Izu-Ogasawara Trench) • 38°N (Japan Trench)

  10. Circulation pattern in the vicinity of ECS • Qiu and Imasato (1990).The annual mean pattern of surface current derived from GEK data between 1953 and 1984. • Lie et al. (1998).The annual mean pattern of surface current derived from trajectories of surface drifters between 1989 and 1996.

  11. Circulation pattern in the vicinity of ECS • The present model.The snapshot of the pattern of surface current in Year 35 Day 61.

  12. Model Validation • PN-Line (ECS) : 0 ~ 1000 m depth, (126.2°E, 30.0°N) ~ (128.2°E, 27.5°N). • TK-Line (Tokara Strait) : 0 ~ 1000 m depth, (130.0°E, 28.6°N) ~ (130.5°E, 30.3°N). • ASUKA-Line (South of Japan) : 0 ~ 1500 m depth, (133.0°E, 32.8°N) ~ (136.5°E, 26.0°N). • 34°N (Izu-Ogasawara Trench) : Over 2000 m depth, (140.0°E, 34.0°N) ~ (144.0°E, 34.0°N). • 38°N (Japan Trench) : Over 2000 m depth, (142.0°E, 38.0°N) ~ (148.0°E, 38.0°N).

  13. Vertical current structure normal to PN line • E. Oka and M. Kawabe (1998).Distribution of geostrophic velocity based on the quarterly data of CTD at the PN line during 1988-1994. (a) winter, (b) spring (c) summer, and (d) fall.

  14. Vertical current structure normal to PN line • The present model.Vertical sections of seasonal mean geostrophic current normal to section PN DuringYear 27-29. • Yamashio et al. (1990).Vertical sections of seasonal mean geostrophic current normal to section PN referred to hydrographic and GEK velocity during 1972-1986. Vmax: autumn 103 cm/sec Vmin: spring 72 cm/sec Vcounter about 6 ~9 cm/sec

  15. Vertical current structure normal to PN line • The present model.Vertical sections of seasonal mean geostrophic current normal to section PN inYear 27, 28, and 29. Vmean, max: 98 cm/sec Vcounter: 7 cm/sec • Oka et al. (2003).Distribution of average geostrophic velocity (cm/sec) at the PN line during 1989–97.

  16. Time series of volume transport (VT) across the PN line (1 Sv[≡]106 m3/sec) • Saiki, 1982; Hinata, 1996. Time series of the Kuroshio transport across PN line. • T. Kagimoto et al. (1997).Seasonal transport variations across the PN line. The solid line denotes the geostrophic transport relative to 700 db from Nagasaki Marine Observatory.

  17. Time series of volume transport (VT) across the PN line (1 Sv[≡]106 m3/sec) • The present model.Time series of VT across the PN line duringYear 27-29. The black dashed line: yearly mean of VT ~ 29 Sv Upper Layer: < 100 m depth Intermediate Layer: 100 ~ 700 m depth Deep Layer: > 700 m depth • Long-term mean during 28 years from 1973 to 2000 is 25.8 Sv. (Nagasaki Marine Observatory, Japan Meteorological Agency) • The mean VT is 25.4 Sv based on the hydrographic data from 1973 to 1993. (Hinata 1996)

  18. Vertical current structure normal to TK line • The present model.Vertical sections of seasonal mean geostrophic current normal to section TK inYear 27, 28, and 29. Vmean, max: 53 cm/sec Vcounter: 6 cm/sec • Oka et al. (2003).Distribution of average geostrophic velocity (cm/sec) at the TK line during 1987–97.

  19. Vertical current structure normal to TK line • The present model.Vertical sections of seasonal mean geostrophic current normal to section TK DuringYear 27-29. Vmax: summer 63 cm/sec Vmin: winter 51 cm/sec Vcounter : 4~8 cm/sec

  20. Time series of VT across the TK line • The present model.Time series of VT across the TK line duringYear 27-29. The black dashed line: yearly mean of VT ~ 24 Sv Upper Layer: < 100 m depth Intermediate Layer: 100 ~ 700 m depth Deep Layer: > 700 m depth • Zhu et al. (2006) conducted an inverse calculation based on 101 CTD and 13 XBT/XCTD casts by R/V Chofu-Maru and R/V Shumpu-Maru of the Japan Meteorological Agency from October to December 2000. The total NVTs at section TK is 26.48 Sv.

  21. Vertical current structure normal to ASUKA line • The present model.Vertical sections of seasonal mean geostrophic current normal to section ASUKA inYear 27, 28, and 29. Vmean, max: 66 cm/sec Vcounter: -27 cm/sec • (Upper panel) S. Imawaki (1995). Geostrophic calculation referred to 2000 m in the deep area and at the bottom in the shallow area. • (Lower panel) T. Kagimoto et al. (1997).model.

  22. Time series of VT across the ASUKA line • Imawaki et al. (2001) calculated upper 1000 m transport derived from “absolute geostrophic velocity” which includes the information of the TOPEX/POSEIDON altimeter data and in-situ observations. • T. Kagimoto et al. (1997).The dashed line shows the total transport variations across the ASUKA line.

  23. Time series of VT across the ASUKA line • The present model.Time series of VT across the ASUKA line duringYear 27-29. The black dashed line: yearly mean of VT ~ 2 Sv Upper Layer: < 100 m depth Intermediate Layer: 100 ~ 1500 m depth Deep Layer: > 1500 m depth • Zhu et al. (2006) conducted an inverse calculation based on 101 CTD and 13 XBT/XCTD casts by R/V Chofu-Maru and R/V Shumpu-Maru of the Japan Meteorological Agency from October to December 2000. The total NVTs at section ASUKA is 63.7 Sv.

  24. Eastward and northward velocity at 34°N (trench floor) • S. Fujio et al. (2000) • C1: 34°00.5’N, 141°50.7’E, 4900 m depth; the eastward and northward velocities are -0.2 cm/sec and -1.9 cm/sec, respectively. • F1: 33°59.6’N, 141°50.5’E, 5110 m depth; the eastward and northward velocities are -0.6 cm/sec and -2.5 cm/sec , respectively. The present model. 3-year temporal mean of u and v are -0.09 cm/sec and -5.844 cm/sec, respectively.

  25. Eastward and northward velocity at 34°N (eastern flank) The present model.Time series of VT across the ASUKA line duringYear 27-29. 3-year temporal mean of u and v are 2.94 cm/sec and -14.8469 cm/sec, respectively. • S. Fujio et al. (2000) • O1: 33°56.9’N, 142°31.5’E, 3900 m depth; the eastward and northward velocities are -2.0 cm/sec and 7.3 cm/sec, respectively.

  26. Time series of VT across 34°N • The present model.Time series of VT across 34°N line duringYear 27-29. The black dashed line: yearly mean of VT ~ -308 Sv Upper Layer: < 100 m depth Intermediate Layer: 100 ~ 2000 m depth Deep Layer: > 2000 m depth • S. Fujio et al. (2000) The southward transport above the western flank was estimated to be 5-8 Sv. The northward transport above the eastern flank 5-22 Sv.

  27. Vertical current structure normal to 38°N • The present model.Vertical sections of seasonal mean geostrophic current normal to section 38°N inYear 27, 28, and 29. Vmean, max: 30 cm/sec Vcounter: -45 cm/sec • S. Fujio (2005).Geostrophic velocity referred to 2000 db at 38N.

  28. Time series of VT across 38°N • The present model.Time series of VT across 38 °N line duringYear 27-29. The black dashed line: yearly mean of VT ~ 106 Sv Upper Layer: < 100 m depth Intermediate Layer: 100 ~ 2000 m depth Deep Layer: > 2000 m depth • S. Fujio et al. (2005) used direct current measurements and hydrographic observations to investigate deep currents east of Japan,. Below 2000 m, the deep transports above the trench were southward 5.5 Sv and northward 13.5 Sv.

  29. Conclusion Fair or Good Results: • Vertical current structure: Sections PN, TK, ASUKA, and 38°N. • Zonal and meridional Velocity: Sections 34°N. • Time series of VT: Sections PN and TK. Bad Results: • Time series of VT: Sections ASUKA , 34°N and 38°N. Program: • Add output for 34°N. • The position of 38°N should be slightly modified.

  30. Future Work • Get ready my extended abstract as soon as possible.

  31. Thanks For Your Listening !

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