Summary Report Lecturer: Chia-Ping Chiang Date: 2009/5/14
Model Validation • PCM1 ~ East of Taiwan • PN ~ East China Sea • TK ~ Tokara Strait • PCM5 (ASUKA) ~ South of Japan • 34°N & 38°N ~ East of Japan TAI Domain
PCM1 W. E. Johns et al. (2001) http://woce.nodc.noaa.gov
Near PCM1 W. E. John et al. (2001) • WOCE: Mean volume transports during 1994/9-1996/5 were estimated to be 23.3 Sv with a standard error of 2.0 Sv. Maximum in July-August and a minimum in October. • Liu et al’s (1998): Mean transport estimate of 22.6 Sv at PCM-1 section from repeat CTD/ADCP sections. Model results of Year 37 to Year 39.
Near PCM1 W. E. John et al. (2001)
Near PCM5 (ASUKA) H. Yoshinari et al. (2004) The absolute transport upper 1000 m
Near PCM5 (ASUKA) T. Kigimoto et al. (1997) • (Upper) Geostrophic calculation relative to 2000 meter • (Lower) Model.
Conclusion • Volume transport (VT) across PCM1 section shows similar temporal variation with the observation. The temporal mean of VT agrees well with several results of published paper. While VT across PCM5 section shows comparable result upper than 1000 m. • The temporal mean of the vertical current structure normal the PCM1 line displays a current core at sea surface. For PCM5, a pair of countercurrent cores forms at sea surface and a undercurrent exists under the Kuroshio. • 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.
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 The DUPOM (duo-grid Pacific Ocean Model) 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 • Volume transport 1. 2. 3. • Vertical current structure
Near PN • 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) 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.
Near PN • 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. 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) Quarterly data of CTD and shipboard ADCP from 1987 to 1997.
Near TK • 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). Model results of Year 37 to Year 39.
Future Work • Continue my paper writing.
Near TK E. Oka et al. (2003) • 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.
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.