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Lecturer: Chia-Ping Chiang Data: March/19/2009

Variations of the volume transport and vertical current structure in relation to the path of the Kuroshio. Lecturer: Chia-Ping Chiang Data: March/19/2009. Typical path of the Kuroshio. Large meander (LM) path Nonlarge meander (NLM) path － nearshore (nNLM) － offshore (oNLM) 6: Uragami

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Lecturer: Chia-Ping Chiang Data: March/19/2009

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  1. Variations of the volume transport and vertical current structure in relation to the path of the Kuroshio Lecturer: Chia-Ping Chiang Data: March/19/2009

  2. Typical path of the Kuroshio • Large meander (LM) path • Nonlarge meander (NLM) path － nearshore (nNLM) － offshore (oNLM) 6: Uragami 7: Kushimoto • Kawabe M. (2005), Journal of Oceanography.

  3. Occurrence of Typical paths • Kawabe M. (1985), Journal of the Oceanographical Society of Japan. • Kawabe M. (1995), Journal of Physical Oceanography.

  4. Cycle of the three typical paths • Large meander (LM) path • Nonlarge meander (NLM) path － nearshore (nNLM) － offshore (oNLM) • Kawabe M. (1995), Journal of Physical Oceanography.

  5. Model Description ~ Duo-grids Pacific Ocean Model(DUPOM) Model Domain: • NPB (North Pacific Basin) Domain ~ From 30°S to 60°N and from 150°E to 80°W with a grid resolution of 1/4°. • TAI Domain ~ From 0° to 50°N and from 100°E to 150°E with a grid resolution of 1/8°. • The vertical resolution ~ linear-exponential stretched grid, 26 layers, Z=6, 20, 36, 54, 75, 98, 126, 159, 198, 244, 298, 364, 442, 537, 652, 790, 958, 1161, 1408, 1709, 2075, 2520, 3063, 3725, 4532 m. • Both grids share the same vertical grid. • Varying latitude and uniform longitude grid (Mercator grid). Bathymetry: • Interpolated from unfiltered ETOPO2 depth data • Supplemented with NCOR’s 1-minute high accuracy depth archive. • Based on the 4th order accurate, collocated Arakawa “a” grid DieCAST (Dietrich/Center for Air Sea Technology) model. • The control volume equations include fluxes of the conservation of momentum, heat and salt across control volume faces.

  6. Model Description ~Duo-grids Pacific Ocean Model(DUPOM) Surface wind forcing: • Use interpolated monthly Hellerman and Rosentstein winds (Hellerman and Rosenstein, 1983). • Use Levitus’94 climatology (Levitus and Boyer, 1994) to initialize the model and determine its surface sources of heat and fresh water. Other details: • The northern boundary is closed. The southern boundary condition (30°S) is slow nudging toward climatology in a sponge layer. The bottom is insulated, with non-slip conditions parameterized by a nonlinear bottom drag. • Sub-grid scale vertical mixing is parameterized by eddy diffusivity (for temperature and salinity) and viscosity (for momentum) using a modified Richardson number based approach based on Pacanowski and Philander. • Background lateral viscosity (diffusivity) is 20 m²/s in both domains.

  7. Results and Discussion • PN-Line • TK-Line • ASUKA-Line

  8. PN-Line • PN: Pollution Nagasaki • Location on earth: (126°E, 28.9°N) ~ (128.25°E , 27.5°N) • Depth: 0 ~ 1000 meters • Features: single stable current core and volume transport around 25 Sv (Note: 1 Sv[≡]106 m3/sec) • Location in DUPOM: (123.9375°E, 31.0°N) ~ (128.0625°E , 26.2°N) • The solid line denotes the geostrophic transport relative to 700db from the observation of Nagasaki Marine Observatory • The dash-dotted line denotes the model transport relative to 700 m.

  9. PN-Line • (Upper) Geostrophic calculation with a reference level at 700 m. • (Lower) OGCM.

  10. TK-Line • TK: Tokara Strait • Location on earth: (129.75°E, 28.5°N) ~ (130.8°E , 30.25°N) • Depth: 0 ~ 1000 meters • Features: Two current cores and volume transport around 26 Sv • Location in DUPOM: (130.1875°E, 28.6°N) ~ (130.1875°E , 30.1°N)

  11. TK-Line • TK: Tokara Strait • Location on earth: (129.75°E, 28.5°N) ~ (130.8°E , 30.25°N) • Depth: 0 ~ 1000 meters • Features: Two current cores and volume transport around 26 Sv • Location in DUPOM: (130.1875°E, 28.6°N) ~ (130.1875°E , 30.1°N)

  12. ASUKA-Line • ASUKA: ASUKA Group • Location on earth: (133.0°E, 33.0°N) ~ (135.5°E , 26.0°N) • Depth: 0 ~ 2000 meters • Features: A pair of opposite currents and volume transport 20~60 Sv • Location in DUPOM: (132.9375°E, 33.0°N) ~ (136.6875°E , 26.0°N) • The solid line denotes the geostrophic transport relative to 700db from the observation of Nagasaki Marine Observatory • The dash-dotted line denotes the model transport relative to 700 m.

  13. ASUKA-Line • (Upper) Geostrophic calculation with a reference level at 2000 m. • (Lower) OGCM.

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