A comparison of two vertical-mixing schemes in a Pacific Ocean general circulation model

The upper Pacific Ocean Current and temperature have been simulated by a th ree-dimensional ocean general circulation model (OGCM) with two different v ertical-mixing schemes. One corresponds to the modified Richardson number-d ependent scheme of Pacanowski and Philander (PP); the other is adapted from the newly developed K-Profile Parameterization (KPP) scheme. The performan ce of both schemes in a Pacific OGCM is evaluated under the same model conf iguration 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 tr opical thermal and current structures; however, KPP is better than PP in se veral important aspects. For example, the KPP scheme simulates a more reali stic thermocline and significantly reduces the cold surface temperature bia s in the eastern equatorial Pacific. The depth of the maximum Equatorial Un dercurrent simulated by the KPP scheme is much closer to the observation. I n the extratropics the KPP scheme is significantly better than the PP schem e in simulating the thermal and current structures, including the annual me an, annual cycle, and interannual-to-interdecadal variability.