두 가지 연직혼합방안에 따른 해양대순환모형 혼합층깊이 및 상층수온 모사 민감도 비교
A Comparison of Two Vertical-Mixing Schemes on the Simulation of the Mixed Layer Depth and Upper Ocean Temperature in an Ocean General Circulation Model
2
조회
0
다운로드
0
인용
0
참고문헌
키워드
초록
Vertical and horizontal mixing processes in the ocean mixed layer determine sea surface temperature and temperature variability. Accordingly, simulating these processes properly is crucial in order to obtain more accurate climate simulations and more reliable future projections using an ocean general circulation model (OGCM). In this study, by using Modular Ocean Model version 4 (MOM4) developed by Geophysical Fluid Dynamics Laboratory, the upper ocean temperature and mixed layer depth were simulated with two different vertical mixing schemes that are most widely used and then compared. The resultant differences were analyzed to understand the underlying mechanism, especially in the Tropical Pacific Ocean where the differences appeared to be the greatest. One of the schemes was the so-called KPP scheme that uses K-Profile parameterization with nonlocal vertical mixing and the other was the N scheme that was rather recently developed based on a second-order turbulence closure. In the equatorial Pacific, the N scheme simulates the mixed layer at a deeper level than the KPP scheme. One of the reasons is that the total vertical diffusivity coefficient simulated with the N scheme is ten times larger, at maximum, in the surface layer compared to the KPP scheme. Another reason is that the zonal current simulated with the N scheme peaks at a deeper ocean level than the KPP scheme, which indicates that the vertical shear was simulated on a larger scale by the N scheme and it enhanced the mixed layer depth. It is notable that while the N scheme simulates a deeper mixed layer in the equatorial Pacific compared to the KPP scheme, the sea surface temperature (SST) simulated with the N scheme was cooler in the central Pacific and warmer in the eastern Pacific. We postulated that the reason for this is that in the central Pacific atmospheric forcing plays an important role in determining SST and so does a strong upwelling in the eastern Pacific. In conclusion, what determines SST is crucial in interpreting the relationship between SST and mixed layer depth.
Abstract
Vertical and horizontal mixing processes in the ocean mixed layer determine sea surface temperature and temperature variability. Accordingly, simulating these processes properly is crucial in order to obtain more accurate climate simulations and more reliable future projections using an ocean general circulation model (OGCM). In this study, by using Modular Ocean Model version 4 (MOM4) developed by Geophysical Fluid Dynamics Laboratory, the upper ocean temperature and mixed layer depth were simulated with two different vertical mixing schemes that are most widely used and then compared. The resultant differences were analyzed to understand the underlying mechanism, especially in the Tropical Pacific Ocean where the differences appeared to be the greatest. One of the schemes was the so-called KPP scheme that uses K-Profile parameterization with nonlocal vertical mixing and the other was the N scheme that was rather recently developed based on a second-order turbulence closure. In the equatorial Pacific, the N scheme simulates the mixed layer at a deeper level than the KPP scheme. One of the reasons is that the total vertical diffusivity coefficient simulated with the N scheme is ten times larger, at maximum, in the surface layer compared to the KPP scheme. Another reason is that the zonal current simulated with the N scheme peaks at a deeper ocean level than the KPP scheme, which indicates that the vertical shear was simulated on a larger scale by the N scheme and it enhanced the mixed layer depth. It is notable that while the N scheme simulates a deeper mixed layer in the equatorial Pacific compared to the KPP scheme, the sea surface temperature (SST) simulated with the N scheme was cooler in the central Pacific and warmer in the eastern Pacific. We postulated that the reason for this is that in the central Pacific atmospheric forcing plays an important role in determining SST and so does a strong upwelling in the eastern Pacific. In conclusion, what determines SST is crucial in interpreting the relationship between SST and mixed layer depth.
참고문헌 (30)
- 이지혜, "GAIA과제: Comparison of the Vertical Mixing Schemes in the OGCM with the Sensitivity to the Latitudinal Dependence", 2012년도 한국 해양과학기술 공동학술대회 초록집, pp.16~ (2012)
- Agrawal YC, "Enhanced dissipation of kinetic-energy beneath surfacewaves", Nature, 359(6392), pp.219~220 (1992)
- Alexander MA, "Winter-towinter recurrence of sea surface temperature, salinity and mixed layer depth anomalies", Prog Oceanogr, 49(1-4), pp.41~61 (2001)
- Anis A, "The Superadiabatic Surface-Layer of the Ocean during Convection", J Phys Oceanogr, 22(10), pp.1221~1227 (1992)
- Ayotte KW, "An evaluation of neutral and convective planetary boundary-layer parameterizations relative to large eddy simulations", Bound-Lay Meteorol, 79(1-2), pp.131~175 (1996)
- Bleck R, "An Oceanic general circulation model framed in hybrid isopycnic-Cartesian coordinates (Vol.4, p.55, 2002)", Ocean Model, 4(2), pp.219~219 (2002)
- Carton JA, "A reanalysis of ocean climate using Simple Ocean Data Assimilation (SODA)", Mon Weather Rev, 136(8), pp.2999~3017 (2008)
- Carton JA, "Variability of the oceanic mixed layer, 1960-2004", J Climate, 21(5), pp.1029~1047 (2008)
- Chen D, "A hybrid vertical mixing scheme and its application to tropical ocean models", J Phys Oceanogr, 24(10), pp.2156~2179 (1994)
- DiNezio PN, "Mean climate controls on the simulated response of ENSO to increasing greenhouse gases", J Climate, 25(21), pp.7399~7420 (2013)
- Ekman VW, "On the influence of the earth's rotation on ocean currents", Ark Mat Astr Fys, 2(11), pp.1~53 (1905)
- Elements of MOM4p1, "Griffies SM", NOAA Geophysical Fluid Dynamics Laboratory, 444~ (2009)
- Griffies SM, "The Large and Yeager (2004) dataset and CORE", NOAA Geophysical Fluid Dynamis Laboratory, 5~ (2004)
- Halliwell GR, "Evaluation of vertical coordinate and vertical mixing algorithms in the HYbrid-Coordinate Ocean Model (HYCOM)", Ocean Model, 7(3-4), pp.285~322 (2004)
- Large WG, "Modeling and parameterizing the ocean planetary boundary layer", Nato Adv Sci IC-Mat, 516, pp.81~120 (1998)
- Large WG, "Oceanic vertical mixing - a review and a model with a nonlocal boundarylayer parameterization", Rev Geophys, 32(4), pp.363~403 (1994)
- Li XJ, "A comparison of two vertical-mixing schemes in a Pacific Ocean general circulation model", J Climate, 14(7), pp.1377~1398 (2001)
- Mailhot J, "A finite-element model of the atmospheric boundary-layer suitable for use with numerical weather prediction models", J Atmos Sci, 39(10), pp.2249~2266 (1982)
- Mellor GL, "Development of a turbulence closure-model for geophysical fluid problems", Rev Geophys, 20(4), pp.851~875 (1982)
- Montegut CD, "Mixed layer depth over the global ocean: An examination of profile data and a profile-based climatology", J Geophys Res-Oceans, 109(C12003) (2004)[DOI]
- NCAR, "NCAR ASCII Version of ETOPO5 earth surface elevation", Data Support Section (National Center for Atmospheric Research, ~ (1989)
- The NCAR CSM Ocean Model, "NCAR", National Center For Atmospheric Research Boulder, 75~, pp.NCAR (1996), TN- 423+STR
- Noh Y, "Dynamics of diurnal thermocline formation in the oceanic mixed layer", J Phys Oceanogr, 26(10), pp.2183~2195 (1996)
- Noh Y, "Simulation of more realistic upper-ocean processes from an OGCM with a new ocean mixed layer model", J Phys Oceanogr, 32, pp.1284~1307 (2002)
- Noh Y, "Simulations of temperature and turbulence structure of the oceanic boundary layer with the improved near-surface process", J Geophys Res- Oceans, 104(C7), pp.15621~15634 (1999)
- O'Brien JJ, "A note on the vertical structure of the eddy exchange coefficient in the planetary boundary layer", J Atmos Sci, 27, pp.1213~1215 (1970)
- Osborn T, "Measurements of bubble plumes and turbulence from a submarine", Atmos Ocean, 30(3), pp.419~440 (1992)
- Pacanowski RC, "Parameterization of vertical mixing in numerical-models of tropical oceans", J Phys Oceanogr, 11(11), pp.1443~1451 (1981)
- Price JF, "Diurnal cycling - observations and models of the upper ocean response to diurnal heating, cooling, and wind mixing", J Geophys Res-Oceans, 91(C7), pp.8411~8427 (1986)
- Thomson RE, "Estimating mixed layer depth from oceanic profile data", J Atmos Ocean Tech, 20(2), pp.319~329 (2003)