Effects of vertical mixing scheme on upper ocean simulation of the East Sea

Abstract

This study investigates effects of four different parameterizations of vertical mixing on the East Sea circulation, focusing on the seasonal variations of the sea surface temperature (SST) and mixed layer depth (MLD). The considered vertical mixing schemes are Laplacian scheme (L scheme), Pacanowski- Phillander scheme (PP scheme), Mellor-Yamada scheme (MY scheme), and a new scheme (Noh et al. 2002) (NEW scheme). The New scheme, a second-order turbulence closure, was developed considering recent observational evidences such as the enhancement of turbulent kinetic energy near the sea surface (Noh and Kim 1999). Model simulations using GFDL MOM1.1 were started from the rest with horizontally-uniform density field, and integrated for 50 years with in-out flows and monthly-mean climatology of Haney-type heat flux and wind stress. The model sea surface salinity was restored to a monthly climatology with a 10-day timescale. During summer L scheme underestimates the SST, while PP and MY schemes overestimate the SST, compared to climatological SST. NEW scheme produces the SST close to climatological SST. During winter all schemes overestimate the SST up to 4℃ compared to climatological SST. Vertical profiles of the basin-mean temperature show that L scheme produces higher temperature below the thermocline than those of other schemes. The MLD simulated from L scheme is rather large during winter compared to that from other schemes, but the differences in MLD during summer are not significant.