Effects of Vertical Mixing Parameterization on the Mixed Layer Depth over the North Pacific in a Global OGCM

장찬주,강현우 한국해양과학기술원 2009 Ocean science journal Vol.44 No.4

We present MLD variability over the North Pacific Ocean in a global ocean general circulation model and impacts of three different vertical mixing schemes on it, based on statistical measures (annual mean difference, root-mean-square difference and correlation coefficient). The constant vertical mixing scheme tends to underestimate MLD over the whole basin. The Pacanowski-Philander scheme tends to overestimate MLD (> 20 m) in the mid- to high latitude during summer, implying that vertical mixing in the mid- to high latitude may not be represented properly by simple internal mixing mechanisms such as stratification or vertical shear of horizontal velocity. On the other hand, the new vertical mixing scheme (Noh et al. 2002) gives the most consistent MLD and its seasonal and spatial variability when compared with observation. These results suggest that parameterization of vertical mixing has significant effects on simulation of the seasonal and spatial variability of MLD over the North Pacific Ocean. We present MLD variability over the North Pacific Ocean in a global ocean general circulation model and impacts of three different vertical mixing schemes on it, based on statistical measures (annual mean difference, root-mean-square difference and correlation coefficient). The constant vertical mixing scheme tends to underestimate MLD over the whole basin. The Pacanowski-Philander scheme tends to overestimate MLD (> 20 m) in the mid- to high latitude during summer, implying that vertical mixing in the mid- to high latitude may not be represented properly by simple internal mixing mechanisms such as stratification or vertical shear of horizontal velocity. On the other hand, the new vertical mixing scheme (Noh et al. 2002) gives the most consistent MLD and its seasonal and spatial variability when compared with observation. These results suggest that parameterization of vertical mixing has significant effects on simulation of the seasonal and spatial variability of MLD over the North Pacific Ocean.

중해상도 전지구 해양대순환 모형의 상층 수온과 혼합층 깊이 모사 성능 평가

장찬주,강석구,김철호,이흥재,민홍식 한국해양과학기술원 2006 Ocean and Polar Research Vol.28 No.3

We investigated seasonal variations of the upper ocean temperature and the mixed layer depth (MLD) in an eddy-permitting global ocean general circulation model (OGCM) to assess the OGCM performance. The OGCM is based on the GFDL MOM3 which has a horizontalresolution of 0.5 degree and 30 vertical levels. The OGCM was integrated for 68 years using a monthly-mean climatological wind stress forcing. The model sea surface temperature (SST) and sea surface salinity were restored to the Levitus climatology with a time scale of 30 days. Annual-mean model SST shows a cold bias (< 2oC) in the summer hemisphere and a warm bias (> oC) in the winter hemisphere mainly due to the restoring boundary condition of temperature. The model MLD captures well the observed features in most areas, with a slightly deep bias. However, in the Ross Sea and Weddell Sea, the model shows significantly deeper MLD than the climatology--mainly due to weak salinity stratifications in the model. For amplitude of seasonal variation, the model SST is smaller (1~3oC) than the observation largely due to the restoring surface boundary condition, while the model MLD has larger seasonal variation (~50It is suggested that for more realistic simulation of the upper ocean structure in the present eddy-permitting ocean model, more refinements in the surface boundary condition for the thermohaline forcing and parameterization for vertical mixing are required, together with the incorporation of a sea-ice model.

가을철 대한해협 표면혼합층의 단기변화

장찬주,김구,심태보,Jang, Chan-Joo,Kim, Kuh,Shim, Tae-Bo 한국해양학회 1995 韓國海洋學會誌 Vol.30 No.5

To investigate a short-term (from 2 hours to 24 hours) variability of a mixed layer, oceanographical data (water temperature, salinity, current) and meteorological data (wind, air temperature, solar radiation) were collected at a site in the Korea Strait at the interval of one hour for 48 hours from October 12 to 14, 1993. The average rates of temporal variations of the mixed layer depth (MLD) and temperature of the mixed layer (MLT), which are very weakly correlated with the wind stress and buoyancy flux at the sea surface, are about 5.2 m/hour and 0.2$^{\circ}C$/hour, respectively. The mixed layer is relatively shallow when both MLT and MLS (salinity of the mixed layer) are low, while MLD is relatively deep when they are high. MLT shows a sudden decrease or increase. Analysis of satellite infrared images and XBT data shows that sudden increase of MLT is caused by advection of warm water. These results suggest that the short-term variation of the mixed layer in the Korea Strait in autumn, in which surface current is relatively strong and different water masses exist, is mainly determined by advection rather than air0sea interaction such as wind stress or buoyancy flux.

연직혼합모수화가 동해 상층 모사에 미치는 영향

장찬주,임세한,Jang, Chan-Joo,Lim, Se-Han 한국군사과학기술학회 2010 한국군사과학기술학회지 Vol.13 No.6

This study investigates effects of three different parameterizations of vertical mixing scheme on upper ocean simulation of the East Sea, focusing on the seasonal variations of the sea surface temperature(SST) and the mixed layer depth(MLD) using an ocean general circulation model(GFDL MOM1.1). The considered vertical mixing schemes are the Laplacian scheme(L scheme) that use a constant eddy coefficient, the Mellor-Yamada scheme(MY scheme), and a new scheme(Noh scheme). The Noh scheme, a second-order turbulence closure, was developed considering recent observational evidences such as the enhancement of turbulent kinetic energy near the sea surface. During summer L scheme underestimates the SST, while MY scheme overestimates the SST, compared to climatological SST. Noh scheme produces the SST in better agreement with climatological one. During winter all schemes overestimate the SST up to $4^{\circ}C$ 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 winter MLD simulated from L scheme is rather large compared to that from other schemes, but the differences in MLD during summer are not significant.

Seasonal Variation of Global Volume Transport Calculated from an Ocean General Circulation Model

장찬주,김철호,Yign Noh 한국해양과학기술원 2002 Ocean and Polar Research Vol.24 No.1

Seasonal variation in global transport calculated from an ocean general circulation model (OGCM) has been assessed through the comparison with observational estimates. The OGCM based on the GFDL MOM1.1 has horizontal grid interval of 10 and 21 vertical levels, and was integrated for 31 years forced by climatological wind stress, freshwater flux, and heat flux with restoring. General features of the world ocean circulation are well reproduced, which include the western boundary currents such as the Kuroshio and the Agulhas Current, the Equatorial Current system, the Antarctic Circumpolar Current, and the Weddell Sea gyres. Also well resolved is the remarkable seasonal variation in the depth-integrated flows in the northern Indian Ocean due to the monsoonal wind. Monthly variation is found to be dominant in the transport of the Antarctic Circumpolar Current through the Drake Passage in accordance with observational estimates. It has been shown that the mid-latitude depth-integrated flows obey the Sverdrup relation, except for some regions such as continental shelf regions where the interaction between stratification and bottom topography is critical.

Simulation of the Mixed Layer in the Western Equatorial Pacific Warm Pool

장찬주,Yign Noh 한국해양과학기술원 2002 Ocean and Polar Research Vol.24 No.2

The upper ocean in the western equatorial Pacific warm pool during TOGA-COARE IMET IOP was simulated using a one-dimensional turbulence closure ocean mixed-layer model, which considered recent observations, such as the remarkable enhancement of turbulent kinetic energy near the ocean surface. The shoaling/deepening of the mixed layer and warming/cooling subsurface water in the model were in reasonable agreement with the observations. There was a significant improvement in simulating the cooling trend of the sea surface temperature under a westerly wind burst with heavy rainfall over previous simulations using bulk mixed-layer models. By contrast, the simulated sea surface salinity (SSS) departed significantly from the observed SSS, especially during a westerly burst and the subsequent restratification period, which might be due to 3-D control processes, such as downwelling/upwelling or advection.

해양혼합층 모형과 해양 대순환모형의 접합 : 상층 해양 과정의 개선

장찬주,노의근,김선태,김정우 한국기상학회 2000 한국기상학회 학술대회 논문집 Vol.2000 No.-

지역기후 접합모델링을 이용한 우리나라 해면수온 미래변화 시범전망

장찬주(Chan Joo Jang),신호정(Ho Jeong Shin),정희석(Hee seok Jung),김철호(Cheol Ho Kim) 한국연안방재학회 2017 한국연안방재학회지 Vol.4 No.1

In spite of an increasing demand on the detailed information on climate change, future climate projections for Korean waters have been conducted very limitedly. Even for the regional climate projections, most of the previous studies used a regional ocean-only model forced by a global model projection result for the atmosphere and thus could not properly simulate the air-sea interactions on a high resolution. The goal of this study is to develop a regional climate coupled model (RCCM) for the Northwest Pacific and present a future climate projection in Korean waters with including high-resolution air-sea interaction effects. In this paper, we present preliminary results focusing on sea surface temperature (SST) changes projected for Korean waters using the RCCM developed for the Northwest Pacific. The RCCM consists of an ocean model, Regional Ocean Modeling System (ROMS) and an atmospheric model, Weather Research Forecast (WRF). The projection results show some prominent features such as a considerable surface warming in the East Sea relative to the Yellow and East China Sea and a stronger warming in summer than in winter. Compared to the ocean-only model result, the RCCM result shows a significant difference in the projected SST, especially in the Yellow Sea, implying that the regional climate modeling allowing air-sea interaction can have a considerable influence on a future climate change projection.

한국해 해양열파

장찬주(Chan Joo Jang),최원근(Wonkeun Choi) 한국에너지기후변화학회 2021 한국에너지기후변화학회 학술대회 Vol.2021 No.5

남극해 여름 클로로필 경년 변동: 엔소의 영향

김용선,장찬주,손영백 한국해양과학기술원 2015 Ocean and Polar Research Vol.37 No.2

The Southern Ocean (SO) plays a primary role in global climate by storing and transporting anthropogenic carbon dioxide through the meridional overturning circulation and the biological pumping process. In this study, we aim to investigate interannual variability of summer chlorophyll concentration in the SO and its relation with the El Niño Southern Oscillation (ENSO), using satellite ocean color data covering 16 years from 1997 to 2012. During El Niño periods, chlorophyll concentration tends to increase in the subtropics (north of the subantarctic front). This chlorophyll increase is likely linked to El Niñoinduced surface cooling that increases nutrient supply through enhanced vertical mixing in the subtropics. On the other hand, the subpolar gyres show localized chlorophyll changes in response to the ENSO. The localized response seems to be primarily attributed to changes in sea-ice concentrations. Our findings suggest that ENSO contributes interannual variability of chlorophyll in the SO through different mechanisms depending on regions.