동해 순환 모델링에서 순환에 미치는 연직 혼합 방안의 영향

Abstract

Vertical mixing plays a crucial role in upper ocean processes such as sea surface temperature (SST) and mixed layer depth (MLD). Effects of parameterization of vertical mixing have been investigated intensively for modeling of both the global ocean and regional oceans. Few modeling efforts for the East Sea, however, have been paid to effects of vertical mixing. We investigate effects of vertical mixing parameterization on the East Sea circulation using four different mixing schemes, focusing on the seasonal variations of the SST and MLD. The considered vertical mixing schemes are constant mixing scheme (hereafter, C scheme), Pacanowski-Phillander scheme (PP scheme), Mellor-Yamada scheme (MY scheme), and a new scheme (NEW). New scheme, a second-order turbulence closure, has been developed considering recent observational evidences such as the enhancement of turbulent kinetic energy near the sea surface. Model simulations with GFDL MOM1.1 were started from the rest with horizontally-uniform density field, and integrated for 50 years with in-out flows and a monthly-mean climatology of Haney-type heat flux and wind stress. During summer C scheme underestimates the SST, while PP and MY schemes overestimate the SST, compared to climatological SST. The summer SST from NEW scheme is much closer to the climatology. During winter all schemes overestimate the SST up to 4℃ compared to climatological SST. Vertical profiles of basin-mean temperature show that C scheme produces higher temperature below the thermocline than that of other schemes. The MLD simulated from C scheme is rather large during winter compared to that from other schemes, while the differences in MLD during summer are not significant. Deep mixed layer near Vladivostok associated with the wintertime convection is not simulated properly regardless of vertical mixing schemes, which significantly alters deep water temperature and salinity. The NEW scheme improves significantly the seasonal variation of heat s