A Comparison of Two Vertical-Mixing Schemes in a Pacific Ocean General Circulation Model

• Published in: Journal of climate Vol. 14; no. 7; pp. 1377 - 1398
• Main Authors: Li, Xianjin, Chao, Yi, McWilliams, James C., Fu, Lee-Lueng
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01.04.2001
• Subjects: Boundary layers; Buoyancy; Climate models; Climatology; Comparative analysis; Diffusion coefficient; Earth, ocean, space; Exact sciences and technology; External geophysics; Marine; Modeling; Ocean currents; Oceans; Physics of the oceans; Thermohaline structure and circulation. Turbulence and diffusion; Turbulence; Velocity; Pacific Ocean; I, Pacific; Temperature distribution; Parametrization; Undercurrent; General circulation models; Annual variation; Ocean circulation; Bias; Surface temperature; Thermocline; Boundary condition; Interannual variation; Three dimensional model; Sea current; Depth profile; Interdecadal variation; Numerical simulation; Performance; Richardson number
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/1520-0442(2001)014<1377:ACOTVM>2.0.CO;2

The upper Pacific Ocean Current and temperature have been simulated by a three-dimensional ocean general circulation model (OGCM) with two different vertical-mixing schemes. One corresponds to the modified Richardson number–dependent scheme of Pacanowski and Philander (PP); the other is adapted from the newly developedK-Profile Parameterization (KPP) scheme. The performance of both schemes in a Pacific OGCM is evaluated under the same model configuration and boundary conditions. Model and data comparisons are made for the mean state, annual cycle, and interannual-to-interdecadal variability. In the Tropics, both the PP and KPP schemes produce reasonably realistic tropical thermal and current structures; however, KPP is better than PP in several important aspects. For example, the KPP scheme simulates a more realistic thermocline and significantly reduces the cold surface temperature bias in the eastern equatorial Pacific. The depth of the maximum Equatorial Undercurrent simulated by the KPP scheme is much closer to the observation. In the extratropics the KPP scheme is significantly better than the PP scheme in simulating the thermal and current structures, including the annual mean, annual cycle, and interannual-to-interdecadal variability.