American Meteorological Society;Boston, MA: American Meteorological Society
摘要:
摘要： AbstractThe North Pacific Subtropical Countercurrent (STCC) has a weak eastward velocity near the surface, but the region is populated with eddies. Studies have shown that the STCC is baroclinically unstable with a peak growth rate of 0.015 day−1 in March, and the ~60-day growth time has been used to explain the peak eddy kinetic energy (EKE) in May observed from satellites. It is argued here that this growth time from previously published normal-mode instability analyses is too slow. Growth rates calculated from an initial-value problem without the normal-mode assumption are found to be 1.5 to 2 times faster and at shorter wavelengths, due to the existence of (i) nonmodal solutions and (ii) sea surface temperature front in the mixed layer in winter. At interannual time scales it is shown that because of rapid surface adjustments, the STCC geostrophic shear, hence also the instability growth, is approximately in phase with surface forcing, leading to EKE modulation that peaks approximately 10 months later. However, the EKE can only be partially explained by this mechanism of modulation by baroclinic instability. It is suggested that the unexplained variance may be caused additionally by modulation of the EKE by dissipation. 出版者： Boston, MA: American Meteorological Society 出版日期： 2014-03-01 出處： Journal of Physical Oceanography, 2014-03, Vol.44 (3), p.818-833 資源來源： Agricultural & Environmental Science Collection 版權： 2015 INIST-CNRS 版權： Copyright American Meteorological Society Mar 2014 版權： Copyright American Meteorological Society 2014 識別號： ISSN: 0022-3670 識別號： EISSN: 1520-0485 識別號： DOI: 10.1175/jpo-d-13-0162.1 識別號： CODEN: JPYOBT
