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GTS的温盐资料在BCC_GODAS中的同化结果分析
The Assimilation Results of Ocean Temperature and Salinity Data from GTS in BCC_GODAS 2.0
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摘要: 分析了从GTS（全球无线通讯系统）获得的2002—2007年海洋温盐观测资料在国家气候中心第2代全球海洋资料同化系统（BCC_GODAS 2.0）中的同化结果。与SODA (简易海洋同化数据) 资料的比较表明:GTS中的海洋温盐资料同化对模式温盐场的改进之处主要表现在混合层暖区的范围和中心强度、温跃层中温度槽脊的深度、温跃层附近的温度梯度以及盐度高、低值区的范围和中心强度等方面，同化后全球温盐场的均方根误差得到一定程度的降低。挑选位于不同海区的单点温盐廓线与ARGO (地转海洋学实时观测阵) 观测作了进一步比较，结果表明：大多数情况下，同化后温盐廓线的均方根误差得到明显降低，模拟的温盐垂向分布特征也更为准确。与TAO (热带大气海洋观测网) 资料的比较也同样表明:同化后的温盐场特征会得到一定程度改善。Abstract: Ocean temperature and salinity observations data from GTS (Global Telecommunication System) are assimilated in second generation global ocean data assimilation system of Beijing Climate Center (BCC_GODAS 2.0) and the results are analyzed. First, the comparison with SODA (Simple Ocean Data Assimilation) reveals the vertical distribution features of root mean square error (RMSE) of global temperature and salinity in model and assimilation system. The analysis shows that, for the RMSE of temperature with assimilation, compared with the results without assimilation, it has a slight decline with a range of 0—0.3 ℃ in the sea surface layer, and an obvious descent with a range of 0.1—0.7 ℃ in depth from about 100 m to deep layer, but has no obvious variation in depth from the middle and lower mixed layer to about 100 m. For the RMSE of salinity after assimilation, it has a descent with a range of 0—0.2 psu in depth from ocean surface to deep layer. Second, further comparison is made for some vertical cross sections, including the zonal cross section along equator, the meridional cross section along 165°E in Pacific Ocean, the meridional cross section along 30°W in Atlantic Ocean, the longitudinal cross section along 90°E in Indian Ocean. The results show that, generally speaking, the GTS data assimilation improves the temperature and salinity simulation in many aspects including the extension and central intensity of warm sector in mixed layer, the depth of temperature ridge and trough in thermocline, the temperature gradient near thermocline, the extension and central intensity of high and low salinity sector, and so on. Moreover, the further comparison with some ARGO (Array for Real time Geostrophic Oceanography) observation indicates that, in most cases, the RMSE of temperature and salinity profiles has an obvious descent after assimilation, leading to more accurate vertical distribution features of temperature and salinity simulations. For selected single point profiles in different ocean areas in January, after assimilation, the RMSE of temperature and salinity decrease by 0.49 ℃ and 0.19 psu, respectively; for selected profiles in July, the descent of RMSE of temperature and salinity is 0.87 ℃ and 0.18 psu, respectively. The comparison with TAO (Tropical Atmosphere Ocean) data also shows that the assimilation can improve the temperature and salinity features to a certain extent. The BCC_GODAS 2.0 has superiority in some degree in ocean data assimilation, however, there is still some deficiency, and the assimilation effect is not very good in some areas or periods, which may be induced by lack of observations, uncertainties of the data, the imperfection of assimilation system, as well as the simulation capability of model, and so on.
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图 1 2002—2007年6年平均的全球温度､盐度均方根误差的廓线分布 (实线为BCC_GODAS同化结果, 虚线为MOM4模拟)
Fig. 1 The profiles of 6-year averaged global temperature and salinity RMSE during 2002—2007 (solid line: assimilated by BCC_GODAS; dashed line:simulated by MOM4)
图 2 2002—2007年7月温度 (单位:℃)､盐度 (单位:psu) 场沿赤道的深度-纬向剖面特征
Fig. 2 The depth-zone cross section of temperature (unit:℃) and salinity (unit:psu) fields along equator in July during 2002—2007
图 3 2002—2007年7月温度 (单位:℃)､盐度 (单位:psu) 场沿165°E的深度-经向剖面特征
Fig. 3 The depth-meridian cross section of temperature (unit:℃) and salinity (unit:psu) fields along 165°E in July during 2002—2007
图 6 2007年1月和7月的模式 (MOM4)､同化结果 (BCC_GODAS) 及ARGO温盐廓线的比较
Fig. 6 The comparison of temperature and salinity profiles among model results (MOM4), assimilation results (BCC_GODAS), and ARGO observations in January and July of 2007
图 7 2002年1月—2007年12月的模式及同化结果的温度场 (单位:℃)､盐度场 (单位:psu) 与TAO资料的比较
Fig. 7 The comparison of temperature (unit:℃) and salinity (unit:psu) fields among MOM4, BCC_GODAS and TAO from January 2002 to December 2007
表 1 模式和同化结果中部分温盐廓线的均方根误差
Table 1 The RMSE of some temperature and salinity profiles in model and assimilation results
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