An Assessment of Southern Ocean Circulation Simulation by LASG/IAP Climate system Ocean Model
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摘要: 使用中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室(LASG/IAP)开发的第三代气候海洋模式(LASG/IAP Climate system Ocean Model version 3, LICOM3.0)低分辨率版本在海洋模式比较计划(Ocean Model Intercomparison Project, OMIP)试验中的模拟数据,描述了南极绕极流(Antarctic Circumpolar Current, ACC)和南大洋经向翻转环流(Meridional Overturning Circulation, MOC)在1958~2009年的平均状态及其变化,并与已有的模式模拟结果和观测结果对比以评估LICOM模式的模拟效果。通过对比已有模式模拟数据发现,LICOM3.0模式模拟的ACC和南大洋MOC在两组OMIP试验中平均状态相仿、结果在合理范围内,但OMIP1试验中海表强迫的变化趋势较OMIP2试验中的变化更大,得到的环流输送在OMIP1试验中增长趋势也更大。Abstract: An analysis of the Antarctic Circumpolar Circulation (ACC) and the southern ocean Meridional Overturning Circulation (MOC) simulated by the LICOM3.0 using the model outputs obtained from the Ocean Model Intercomparison Project (OMIP) is presented in this article. The mean, variability, and trends of the ACC and MOC over the 1958–2009 period are focused and their relationships with the surface forcing are studied. The model results are compared with available observations, simulation results from other models having finer resolutions, and also with theoretical constraints to check the reliability of the simulations. Generally, the ACC and the Southern Ocean MOC simulated by LICOM3.0 have a similar and reasonable mean state in the two experiments, presenting similar trends from 1958–2009. However, Southern Ocean transport has a larger trend in the OMIP1 experiment, which is related to surface forces. Their correlation needs to be studied further.
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图 1 整个时段和前后两个时段平均的纬向平均纬向风应力,其中实线为1958~2009,虚线为1958~1967,点线为2000~2009,点横线为距平(最后十年均值减去最初十年均值)。蓝色和红色分别为OMIP1和OMIP2结果
Figure 1. Zonal-mean zonal wind stress for the entire period (1958–2009, solid curves), first decade (1958–1967, dashed curves), last decade (2000–2009, dotted curves), and the anomalies (last decade minus first decade, point horizontal curves). OMIP1 and OMIP2 were the blue and red outcomes, respectively
图 3 (a)OMIP1和 OMIP2的6个循环中南极绕极环流(Antarctic Circumpolar Circulation, ACC)体积输送随时间(1958~2009 年)的变化;(b)各模式结果比较:△表示 22 个 CMIP3 模式 1976~2006 年的平均值 144.6±74.1 Sv(Sen Gupta et al., 2009),*表示 23 个 CMIP5 模式 1976~2006 年平均值 155±51 Sv(Meijers et al., 2012),▽表示 34 个CMIP6 模式 1986~2005 年平均值 137±37 Sv(Beadling et al., 2020),x为 COREII 驱动多模式模拟得到的 1958~2007 的平均值 136.8±28 Sv(Farneti et al., 2015),o 和□分别表示 1993~2000 年和2007~2011 年观测的平均值 136.7±7.8 Sv(Cunningham et al., 2003)和 127.7±8.1 Sv(Chidichimo et al., 2014)
Figure 3. (a) Annual mean Antarctic Circumpolar Circulation (ACC) volume transport over time (1958–2009) in six cycles of OMIP1 and OMIP2; (b) comparison of model simulations: △ represents the mean data (144.6±74.1 Sv) of 22 CMIP3 models in 1976–2006 (Sen Gupta et al., 2009), * represents the mean data (155±51 Sv) of 23 CMIP5 models in 1976–2006 (Meijers et al., 2012), ▽ represents the mean data (137±37 Sv) of 34 CMIP6 models in 1986–2005 (Beadling et al., 2020), x represents the mean data (136.8±28 Sv) in 1958–2007 (Farneti et al., 2015), o and □ represent the observed mean data (136.7±7.8 Sv) of 1993–2000 (Cunningham et al., 2003) and mean data (127.7±8.1 Sv) of 2007–2011 (Chidichimo et al., 2014), respectively
图 4 OMIP1(蓝线)和OMIP2(红线)第六个循环(1958~2009年)年平均的ACC体积输送。 o和□分别表示1993~2000年和2007~2011年观测的平均值136.7±7.8 Sv(Cunningham et al., 2003)和127.7±8.1 Sv(Chidichimo et al., 2014)
Figure 4. Annual mean ACC volume transport over the sixth cycle (1958–2009) in OMIP1 (blue curve) and OMIP2 (red curve). o and □ represented the averages of 136.7±7.8 Sv (Cunningham et al., 2003) and 127.7±8.1 Sv (Chidichimo et al., 2014) observed in 1993–2000 and 2007–2011, respectively
图 5 OMIP1(左)和OMIP2(右)第六个循环(1958~2009年)年平均的ACC体积输送和海洋上层(−1500~0 m深度)位密度65°S和40°S的梯度
$ \Delta \rho $ (以−2000 m为参考)的散点图Figure 5. Scatter plots of OMIP1 (left) and OMIP2 (right) of the sixth cycle (1958–2009) with a time-mean ACC volume transport and a gradient ∆ρ (with reference to −2000 m) of the upper ocean (−1500−0 m) with densities of 65°S and 40°S
图 6 OMIP1(左)和OMIP2(右)第六个循环(1958~2009年)平均的纬向平均位密度(等值线,单位:kg/m3;以−2000 m为参考面,)以及纬向平均温度的线性十年变化(阴影),即年平均值随时间(1958~2009年)的10倍线性变化值
Figure 6. Time-mean (1958−2009) and zonal-mean potential densities (contours, unit: kg/m3; referenced to -2000 m) computed over the sixth CORE-II cycle in OMIP1 (left) and OMIP2 (right). Also included are the linear decadal trend of zonal-mean temperature (shadings), which means ten times the linear trend of yearly-mean value
图 7 OMIP1(左)和OMIP2(右)第六个循环(1958~2009年)平均的纬向平均位密度(等值线,单位:kg/m3;以−2000 m为参考面)以及纬向平均盐度的线性十年变化(阴影)
Figure 7. Time-mean (1958−2009) and zonal-mean potential densities (contours, units: kg/m3; referenced to -2000 m) computed over the sixth CORE-II cycle in OMIP1 (left) and OMIP2 (right). Also included are the linear decadal trend of zonal-mean salinity (shadings)
图 9 (a)OMIP1和(b)OMIP2第六个循环(1958~2009年)平均的纬向平均位密度(等值线,单位:kg/m3;以−2000 m为参考面)以及纬向平均位密度的十年变化(阴影),即年平均值随时间(1958~2009年)的10倍线性变化值
Figure 9. Linear decadal trend in zonal mean density for the years 1958–2009, computed over the sixth CORE-II cycle in (a) OMIP1 and (b) OMIP2. Also included are the linear decadal trend of zonal-mean density, which means ten times the linear trend of yearly-mean value
图 10 OMIP1(蓝线)和OMIP2(红线)第六个循环(1958~2009年)年平均ACC体积输送距平和SAM指数。SAM指数分别是基于CORE-II和JRA55-do数据集中纬向平均海平面气压在40°S和65°S的标准值之差
Figure 10. Annual mean ACC volume transport (solid lines) and SAM index (dashed lines) for the years 1958–2009, computed over the sixth CORE-II cycle in OMIP1 (blue lines) and OMIP2 (red lines). SAM index is based on the difference between the standard zonal-mean sea level pressure at 40oS and 65oS in the CORE-II and JRA55-do data sets, respectively. r1/r2 represents correlation coefficients
图 11 (a)OMIP1和(b)OMIP2第六个循环平均的(1958~2009年)MOC流函数
${\varPsi }_{\rm res}\left(y,z\right)$ 的深度—纬度剖面。流函数为正时,MOC的流动方向为顺时针;等值线范围是−30~30 Sv,间隔是3 SvFigure 11. Depth–latitude cross section of time-mean (1958–2009) residual meridional overturning circulation function
${\varPsi }_{\rm res}\left(y,z\right)$ , computed over the sixth CORE-II cycle in (a) OMIP1 and (b) OMIP2. The circulation is clockwise with positive data; the contour ranges from −30−30 Sv and their interval is 3 Sv图 12 (a)OMIP1和(b)OMIP2第六个循环平均的(1958~2009年)欧拉平均环流流函数在深度—纬度坐标上的分布。流函数为正时为顺时针,等值线范围是−30~30 Sv,间隔是3 Sv
Figure 12. Depth–latitude cross section of time-mean (1958–2009) Euler-mean meridional overturning circulation function
$\stackrel{-}{{\varPsi }}\left(y,z\right)$ , computed over the sixth CORE-II cycle in (a) OMIP1 and (b) OMIP2. Positive values imply a clockwise circulation; the contour ranges from −30−30 Sv and their interval is 3 Sv图 13 (a)OMIP1和(b)OMIP2第六个循环平均的(1958~2009年)涡致环流流函数在深度—纬度坐标上的分布。流函数为正时为顺时针,等值线间隔是1 Sv
Figure 13. Depth–latitude cross section of time-mean (1958–2009) Eddy-induced meridional overturning circulation function
${{\varPsi }}^{*}\left(y,z\right)$ , computed over the sixth CORE-II cycle in (a) OMIP1 and (b) OMIP2. Positive values imply a clockwise circulation; the contour ranges from −10−10 Sv and their interval is 1 Sv图 14 OMIP1试验第六个循环平均的(1958~2009年)(a)欧拉流函数
$\stackrel{-}{{\varPsi }}$ 、(b)涡致流函数${{\varPsi }}^{*}$ 和(c)余差流函数${{\varPsi }}_{\rm res}$ 的线性十年变化;(d−f)与(a−c)相同,但为OMIP2的结果。等值线范围是−0.4~1.6 Sv (10 a)−1,间隔是0.2 Sv (10 a)−1Figure 14. Linear decadal trend of the zonally-averaged (a) Euler-mean stream function
$\stackrel{-}{{\varPsi }}$ , (b) eddy-induced stream function${{\varPsi }}^{*}$ , and (c) residual stream function${{\varPsi }}_{\rm res}$ for the years 1958–2007 in OMIP1; (d−f) the same as (a−c), but for OMIP2. The contour ranges from −0.4−1.6 Sv (10 a)−1 and their interval is 0.2 Sv (10 a)−1图 15 南大洋MOC上层环流输送年际平均值距平(1958~2009年)和SAM指数的时间序列;SAM(OMIP1)和SAM(OMIP2)分别是基于CORE-II和JRA55-do数据集中纬向平均海平面气压在40°S和65°S的标准值之差
Figure 15. Annual mean residual MOC volume transport (solid lines) and SAM index (dashed lines) for the years 1958–2009 in OMIP1 (blue lines) and OMIP2 (red lines). SAM index is based on the difference between the standard zonal-mean sea level pressure at 40oS and 65oS in the CORE-II and JRA55-do data sets, respectively. r1/r2 represents correlation coefficients
表 1 CORE-II和JRA55-do强迫场时空分辨率
Table 1. Spatiotemporal resolution in CORE-II and JRA55-do forcing data
大气数据集中的强迫变量的分辨率 10 m风场、温度、湿度、海平面气压 表面向下短波辐射、向下长波辐射 日降水量 河水径流 海冰密集度 CORE-II 6 h,1.875° 1 d,1.875° 1月,1.875° — 1 d,0.5° JRA55-do 3 h,0.5625°
(瞬时值)3 h,0.5625°
(平均值)3 h,0.5625°
(含固态和液态)1 d,0.25° — 表 2 LICOM模式模拟的ACC体积输送的平均值、变化率、前后十年变化、与风应力和经向密度变化的相关系数
Table 2. The average, rate of change, decadal trend, and corelation coefficents with wind stress and meridional density change of volume ACC transport shown by LICOM are reported
数据来源 平均值/Sv 变化率 十年变化/ Sv (10 a)−1 与风应力
相关系数与经向密度变
化相关系数LICOM(OMIP1)(1958~2009年) 131.1±3.3 4.06% 1.80 0.81 0.81 LICOM (OMIP2)(1958~2009年) 131.9±2.3 1.76% 1.03 0.73 0.59 MMM*(Farneti et al., 2015;1958~2007年) 136.8±28 6.56%±0.98% 2.70±0.55 − − CMIP6(Beadling et al., 2020;1986~2005年) 137±37 − − − − CMIP5 (Meijers et al., 2012;1976~2006年) 155±51 − − − − CMIP3 (Sen Gupta et al., 2009;1976~2006年) 144.6±74.1 − − − − 观测值(Cunningham et al., 2003;1993~2000年) 136.7±7.8 − − − − 观测值(Chidichimo et al., 2014;2007~2011年) 127.7±8.1 − − − − 观测值(Koshlyakov et al., 2007;2005年) 130 − − − − 观测值(Renault et al., 2011;2006年) 136.3 − − − − 注:变化是2000~2009年相较于1958年改变的平均百分比,10年变化是ACC输送在1958~2009年间线性10年变化;相关系数(风应力)和相关系数(经向密度变化)分别是ACC输送与纬向平均纬向风应力峰值变化、经向密度变化(深度上−1500~0 m平均、经向平均位势密度在65°S和40°S间的差值)的相关系数。*引自Farneti et al.(2015)。 -
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