地球物理学报  2013, Vol. 56 Issue (6): 1850-1856 PDF

1. 中国科学院计算地球动力学重点实验室, 北京 100049;
2. 中国科学院大学地球科学学院, 北京 100049

Mean dynamic topography calculated by GOCE gravity field model and CNES-CLS2010 mean sea surface height
WAN Xiao-Yun1,2, YU Jin-Hai1,2
1. Key Laboratory of Computational Geodynamics, Chinese Academy of Sciences, Beijing 100049, China;
2. College of Earth Science, University of Chinese Academy of Sciences, Beijing 100049, China
Abstract: Global mean dynamic topographies (MDT) are computed with three groups of GOCE gravity field models and CNES-CLS2010 mean sea surface height (MSS), and then geostrophic surface currents are also computed. Finally Kuroshio is analyzed emphatically. The results show that the different GOCE gravity field models are stable, i.e., the differences of MDT calculated using different GOCE gravity field models are all less than several centimeters. It indicates the accuracy of geoid provided by GOCE arrives at magnitude of centimeter. The comparison with GRACE shows that GOCE can provide more local information of the currents. Especially for the boundary currents such as Kuroshio and the Gulf Stream which are fast and narrow, the result from GOCE is much clearer and the velocity is more accurate. Hence, GOCE is more appropriate for research on the currents than GRACE..
Key words: GOCE gravity field model      Mean dynamic topography      Ocean current
1 引言

2 计算方法

 (1)

 (2)

3 采用的数据资料

4 结果与讨论 4.1 海面地形

 图 1 不同模型计算所得MDT（单位：m） Fig. 1 MDT calculated with different models (units:m)

 图 2 第二时段直接法、空域法与时域法模型的对比（单位：m） Fig. 2 Comparisons between DIR2, SPA2 and TIM2 (units:m)
 图 3 第二、三时段直接法、时域法各自模型的对比（单位：m） Fig. 3 Comparisons between DIR3 and DIR2, TIM3 and TIM2 (units:m)

4.2 洋流

 图 4 由TIM3及GRACE模型解算的地转流速度图（单位：m/s） Fig. 4 Geostrophic current velocity calculated with TIM3 and GRACE gravity field model (units:m/s)

①从各个洋流，如：黑潮、墨西哥湾流、阿古拉斯海流、巴西洋流、南极洲环流等均可发现GOCE所得结果条纹更细更清晰.如位于60°N，314°E的拉布拉多洋流，GRACE所得结果极为模糊，因为该洋流近岸分支宽度仅约100km，GRACE空间分辨率显然不够；

②赤道附近差异显著，一是因为GOCE的空间分辨率更高，展现了更多的高频信号；二是因为GOCE模型的阶数更高，公式（2）由奇异因子产生的累积误差更大；

③在许多区域，GOCE计算结果局部量值比GRACE所得结果稍大，特别是靠近陆地的边界流，如北半球的黑潮和墨西哥湾流等.

 图 5 GOCE模型和GRACE模型在黑潮流域解算的地转流速度图（单位：m/s） Fig. 5 Geostrophic current velocity of Kuroshio calculated with GOCE and GRACE gravity field models (units:m/s)

①GRACE比GOCE更加平滑，GOCE能显示更多的局部特征；

②在中国台湾北端和日本九州之间的区域，GOCE所得洋流速度约35 cm/s左右，这和Knudsen[20]所给值基本一致（37cm/s），而GRACE引力场模型的计算值仅约27cm/s，由此可见，利用GOCE重力场模型解出的洋流速度较GRACE的结果精度更高；

③在东京以东的海域GRACE所得解也明显偏小.

5 结论