Lecturer: Chia-Ping Chiang Date: 2009/5/7 Summary Report Lecturer: Chia-Ping Chiang Date: 2009/5/7

Introduction ~ Kuroshio M. Andres et al. (2008) S. Itoh et al. (2008)

Theory ~ Model Description Equation of continuity: Equations of momentum: Equation of conservation of salt or energy: Equation of state:

Model Description Bathymetry: Surface wind forcing: The DUPOM (duo-grid Pacific Ocean Model) used herein is based on the fourth-order accurate, collocated Arakawa “a” grid DieCAST (Dietrich/Center for Air Sea Technology) ocean model. Bathymetry: Unfiltered ETOPO5 depth data Interpolation. Supplemented with NCOR’s 1-minute high accuracy depth archive. Surface wind forcing: Interpolated monthly Hellerman and Rosentstein winds (Hellerman and Rosenstein, 1983). Levitus’94 climatology (Levitus and Boyer, 1994) to initialize the model and determine its surface sources of heat and fresh water. Background lateral viscosity (diffusivity) is 20 m²/s in both domains.

Model Validation TAI Domain PCM1 ~ East of Taiwan PN ~ Into East China Sea TK ~ Through Tokara Strait PCM1 (ASUKA) ~ South of Japan 34°N & 38°N ~ East of Japan

PCM1

Near PN T. Kigimoto et al. (1997) Model results of Year 37 to Year 39. The solid line denotes the geostrophic transport relative to 700db from the data of Nagasaki Marine Observatory during 1973 and 1992. The long-term mean relative transport from 1973 to 2000 is 25.8 Sv with a mean seasonal maximum of 27 Sv in summer and minimum of 23.9 Sv in autumn. (Oceanographic Division, Nagasaki Marine Observatory, JMA)

Near PN M. Andres et al. (2008) CPIES+ADCP observation during October 2003 until November 2004 . Model results of Year 37 to Year 39. E. Oka et al. (2003) A current core with a northeastward velocity more than 40 cm/sec from sea surface to depth of 400 db across the PN line. A countercurrent under the Kuroshio. Quarterly data of CTD and shipboard ADCP from 1987 to 1997.

Near TK Model results of Year 37 to Year 39. Observation from spring 1987 to spring 2005 and many estimates of the Kuroshio volume transport through Tokara Strait ranges from 18 Sv to 32 Sv (Bingham and Talley 1991; Yamamoto et al. 1993; Nakano et al. 1994; Yamamoto et al. 1998; Feng et al. 2000; Zhu et al. 2006).

Near TK E. Oka et al. (2003) Model results of Year 27 to Year 29. According to 40 observations at the TK line during 1987–97 , the northern core is located at T2–T5, and the southern core is at T6–T11. Both the northern and southern current cores have a large velocity greater than 40 cm/s in 35 observations out of 40, and only the southern current core has such a large velocity in the remaining five observations. In the 35 observations of double current cores, the northern core has a larger maximum velocity than the southern core in 25 observations (Type 1), and the southern core is stronger in the remaining 10 observations (Type 2). The Kuroshio with the single southern core is called Type 3. There is no case of a single northern core, because the deep part of the Kuroshio always passes through the southern deep gap and forms the southern core. Model results of Year 27 to Year 29. Model results of Year 37 to Year 39.

PCM5(ASUKA)

34°N S. Fujio et al. (2000) Model results of Year 36 Day 198. (Hydrographic observations in 1995) The geostrophic velocity referred to 2000 dbar. A southward current flowed above the western flank, and a northward current flowed above the eastern flank. Unlike in the CM results (from 1987 to 1996), the boundary between the northward and southward velocities was not located above the trench floor.

38°N S. Fujio et al. (2000) (direct current measurements and hydrographic observations from Nov. 1996 to Sep. 1997) Deep currents flowed southward and northward above the western and eastern flanks of the Japan Trench, respectively. Above the abyssal plain east of the trench, the velocity is southward.

Conclusion The volume transport across the PN and TK sections during Year 37 to Year 39 agrees with the results of some literature. The temporal mean of the vertical current structure normal the PN line during Year 37 and Year 39 forms a pair of current core. The snapshot of the vertical current structure normal the 38 degree N in Year 36 forms 2 pairs of current core.

Future Work Continue my paper writing.