| 海潮误差对GRACE时变重力场解算的影响研究 |
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| 引用本文： | 王长青,许厚泽,钟敏,冉将军,周江存.海潮误差对GRACE时变重力场解算的影响研究[J].地球物理学报,2015,58(9):3072-3079. |
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| 作者姓名： | 王长青 许厚泽 钟敏 冉将军 周江存 |
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| 作者单位： | 1. 中国科学院测量与地球物理研究所大地测量与地球动力学国家重点实验室, 武汉 430077;
2. 中国科学院大学, 北京 100049 |
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| 基金项目： | 国家重大科学研究计划(2013CB733305,2012CB957703),国家自然科学基金(41174066,41131067,41374087,41431070,41374025)联合资助. |
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| 摘 要： | 海潮误差是GRACE时变重力场反演中重要的误差源,目前发布的海潮模型中主要包含振幅较大的主潮波分量模型,在时变重力场反演中次潮波的影响也是不可忽略的,因此,GRACE时变重力场反演中的海潮误差主要包括受限于海潮模型误差和次潮波影响.本文利用轨道模拟方法检测了短周期潮波的混频周期以及次潮波对ΔC20,ΔC30的时序特征,并进一步通过轨道模拟结果分析了海潮误差对时变重力场反演的影响,然后通过实测数据解算分析了海潮误差对当前GRACE时变重力场解算的影响,研究发现:(1)利用轨道模拟能够有效地检测短周期潮波的混频周期;(2)时变重力场解算过程中,次潮波的影响大于海潮模型误差的影响;(3)海潮模型误差以及次潮波影响是当前GRACE没有达到基准精度的重要因素之一.
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| 关 键 词： | GRACE 时变重力场反演 轨道模拟 海潮混频周期 次潮波 |
| 收稿时间： | 2015-01-15 |
A study on the effect of ocean tides error in GRACE temporal gravity field recovery |
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| WANG Chang-Qing,XU Hou-Ze,ZHONG Min,RAN Jiang-Jun,ZHOU Jiang-Cun.A study on the effect of ocean tides error in GRACE temporal gravity field recovery[J].Chinese Journal of Geophysics,2015,58(9):3072-3079. |
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| Authors: | WANG Chang-Qing XU Hou-Ze ZHONG Min RAN Jiang-Jun ZHOU Jiang-Cun |
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| Institution: | 1. State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophsics, Chinese Academy of Sciences, Wuhan 430077, China;
2. University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | The ocean tides with periods of about 12 and 24 hours are rarely sampled by GRACE. The tidal signal and their errors can only be recognized after rather long "alias" periods. The ocean tide error is one of the error sources in GRACE temporal gravity field recovery. This paper aimed to study the effect of ocean tide error in GRACE temporal gravity field recovery. Generally, the ocean tide model released involves only the largest tides or main waves. However, the impact of secondary tides on temporal gravity field recovery cannot be negligible as well. Therefore, ocean tide errors in GRACE temporal gravity field recovery contain major wave's error induced by accuracy level of ocean tide model and errors induced by secondary tides.
Differences between the two ocean tide models (FES2004 and EOT08a) were used to estimate the magnitude of ocean tide model errors in this paper. Ocean tide model EOT11a with 18 major ocean tides and EOT11a with 238 secondary tides (plus 18 major ocean tides) were used to check the impact of 238 secondary tides on temporal gravity field recovery. We performed two methods to achieve the above goals: the orbit simulation using GRACE GNV1B products and the real GRACE recovery of monthly gravity solution using the variational equations approach. Based on orbit simulation, we analyzed the spatial distribution of tide model errors in terms of geoid height changes and time series of global spherical harmonic coefficient ΔC20 and ΔC30 induced by each of eight short period tide model errors and 238 secondary tides. Furthermore, we estimated the magnitude of ocean tide model errors and analyzed the impact of 238 secondary tides using the real GRACE recovery of monthly gravity solution.
The analysis of the spatial distribution of ocean tide errors in terms of geoid height changes showed that ocean tide model errors in S2, K2 and M2 had significantly larger magnitudes than errors in other constituents. In addition, spatial distributions of tide model errors in S2 and K2 had long wavelength features and had no significant meridional strips. However, errors induced by 238 secondary tides had large amplitudes and significant meridional strips. Temporal alias errors obtained by orbit simulation analyses showed that alias periods of tide model errors in K2, S2 and P1 had an alias period of 3.7 years, 163 days and 171 days, respectively. These results coincided well with their theoretical values. What's more, global spherical harmonic coefficient changes in ΔC20 and ΔC30 induced by 238 secondary tides mainly showed two different periods. The longer period might be larger than five years, and the shorter period was near 110 days. Orbit simulation results suggested that ocean tide model errors in S2 and K2 exceeded the GRACE baseline accuracy at degree larger than 30 and 18, and all nine short tide models' error exceeded the GRACE baseline accuracy at degree 2~60. The results based on real GRACE observation data also indicated that the ocean tide model errors and the impact of secondary tides exceeded the GRACE baseline accuracy at degree 2~60. The analysis of orbit simulation and real GRACE recovery of monthly gravity solution suggested that the impact of secondary tide on temporal gravity field recovery was larger than ocean tide model errors.
Based on the above investigations, we concluded that: (1)The orbit simulation can effectively detect alias periods of short period ocean tide model errors and also be used to check time series properties of the global spherical harmonic coefficients induced by secondary tides; (2) The impact of secondary tides on the current GRACE temporal gravity field recovery is greater than that of 18 major ocean tide model errors; (3) Ocean tide errors, including ocean tide model errors and the impact of the secondary tides, are important factors why current GRACE does not reach the GRACE baseline accuracy. |
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| Keywords: | GRACE Temporal gravity field recovery Orbit simulation Ocean tide alias period Secondary tides error |
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