Harker Alexander A, Schindelegger Michael, Ponte Rui M, Salstein David A
Institute of Geodesy and Geoinformation, University of Bonn, Nussallee 15, 53115 Bonn, Germany.
Atmospheric and Environmental Research, Inc., Lexington, MA USA.
J Geod. 2021;95(9):110. doi: 10.1007/s00190-021-01555-z. Epub 2021 Sep 7.
We revisit the problem of modeling the ocean's contribution to rapid, non-tidal Earth rotation variations at periods of 2-120 days. Estimates of oceanic angular momentum (OAM, 2007-2011) are drawn from a suite of established circulation models and new numerical simulations, whose finest configuration is on a grid. We show that the OAM product by the Earth System Modeling Group at GeoForschungsZentrum Potsdam has spurious short period variance in its equatorial motion terms, rendering the series a poor choice for describing oceanic signals in polar motion on time scales of less than 2 weeks. Accounting for OAM in rotation budgets from other models typically reduces the variance of atmosphere-corrected geodetic excitation by 54% for deconvolved polar motion and by 60% for length-of-day. Use of OAM from the model does provide for an additional reduction in residual variance such that the combined oceanic-atmospheric effect explains as much as 84% of the polar motion excitation at periods < 120 days. Employing statistical analysis and bottom pressure changes from daily Gravity Recovery and Climate Experiment solutions, we highlight the tendency of ocean models run at a 1 grid spacing to misrepresent topographically constrained dynamics in some deep basins of the Southern Ocean, which has adverse effects on OAM estimates taken along the 90 meridian. Higher model resolution thus emerges as a sensible target for improving the oceanic component in broader efforts of Earth system modeling for geodetic purposes.
我们重新审视了海洋对2至120天周期内地球快速非潮汐自转变化的贡献建模问题。海洋角动量（OAM，2007 - 2011年）的估计值来自一系列既定的环流模型和新的数值模拟，其最精细的配置是在一个[具体网格规格未给出]网格上。我们表明，波茨坦地学研究中心地球系统建模小组的OAM产品在其赤道运动项中存在虚假的短周期方差，这使得该序列在描述小于2周时间尺度上的极移海洋信号时不是一个好的选择。在其他模型的自转预算中考虑OAM，对于去卷积后的极移，通常会使大气校正后的大地测量激发方差降低54%，对于日长则降低60%。使用[具体模型未给出]模型的OAM确实能进一步降低残余方差，使得海洋 - 大气综合效应在周期<120天的情况下能解释高达84%的极移激发。通过统计分析以及每日重力恢复与气候实验解的海底压力变化，我们强调了以1[具体网格规格未给出]网格间距运行的海洋模型在南大洋一些深海盆地中往往会错误表征地形约束动力学的趋势，这对沿90°子午线获取 的OAM估计有不利影响。因此，更高的模型分辨率成为在大地测量目的的地球系统建模更广泛努力中改善海洋成分的一个合理目标。
