The Eastward Subtropical Countercurrent on Isopycnal Surface in the Western North Pacific
Abstract
The monthly circulations on isopycnal surface in the western North Pacific are calculated based on the Navy's Generalized Digital Environmental Model climatological temperature and salinity data on a 1/2 deg x 1/2 deg grid using a P-vector method. The eastward Subtropical Countercurrent (STCC) in the central subtropical gyre has been studied with emphasis on its spatial distribution, vertical structure, volume transport and its nearby eddy phenomenon. The results reproduce the observed feature of STCC, and reveal some new phenomena on isopycnal surface, such as: (1) At sigma theta = 24.6, there is strong seasonal variability in the distribution, origin and flow status of STCC. There is no STCC in January, February and March. (2) From May to October, a branch of the Kuroshio Countercurrent to the south of Japan merges into STCC, which increases the velocity of STCC and widens its width. (3) The velocity vector field shows that STCC and nearby eddies coexist. (4) The eastward volume transport of STCC across 137.5 deg E is the strongest in summer with the maximum of 6.9 Sv ( 1 Sv equivalent to 10(6) M(3) S(-1)) in August, and weaker in spring and autumn with 1.7 Sv in April and 1.6 Sv in November. Most of the transports of STCC occur between isopycnal surfaces 24.0 sigma theta; and 25.0 sigma theta. (5) The distributions of the zonal flow along 137.5 deg E show that the flow core of STCC is between 24.3sigma theta and 24.7sigma theta.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2005
- Accession Number
- ADA575161
Entities
People
- Peter Cheng Chu
- Rongfeng Li
- Xiaobao You
Organizations
- Naval Postgraduate School