Propagation of atmospheric model errors to gravity potential harmonics—impact on GRACE de-aliasing
Propagation of atmospheric model errors to gravity potential harmonics—impact on GRACE de-aliasing
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DOI：
10.1111/j.1365-246x.2010.04669.x
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发表时间：
2010-06
影响因子：
2.8
通讯作者：
Lieselotte Zenner;T. Gruber;A. Jäggi;G. Beutler
中科院分区：
文献类型：
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作者：
Lieselotte Zenner;T. Gruber;A. Jäggi;G. Beutler
由于信号和轨道的时空采样特性，海洋和大气中的高频时变质量再分布对GRACE重力场解产生影响。因此，这些信号与GRACE观测结果之间存在混叠，需要在数据分析过程中通过应用大气和海洋模型数据（去混叠）加以考虑。由于在对真实的GRACE数据进行分析时还不能达到发射前预测的精度，因此去混叠过程和相关的地球物理模型不确定性被认为是GRACE重力场确定中的潜在误差源。因此，本研究旨在改进去混叠过程，以获得更精确的GRACE重力场时间序列。由于这些时间序列提供了对地球系统中综合物质输运的估计，如全球水循环和固体地球物理过程，任何准确性的提高都将导致对结果的地球物理解释的改进。因此，总之，改善去混叠对于更好地理解地球物理过程具有重要意义。通过不再将大气和海洋模型输出视为无误差，可以更深入地了解这种不确定性对去混叠和对所产生的GRACE重力场模型的影响。为此，在第一步中，进行大气和海洋模型参数到去混叠重力场系数的完全误差传播，并分析作为中间重力场结果的GRACE K波段卫星对卫星跟踪（KBR-SST）残差。本文回顾了标准GRACE去混叠过程，并给出了误差传播的数学模型。具体而言，大气输入参数（温度、表面压力、特定湿度、地球势）的不确定性对用于去混叠的重力场位系数的影响在几种情况下显示。最后，去混叠产品（有和没有误差传播）的GRACE重力场解的影响进行了研究的水平上的观测残差。从本研究中得到的结果可以得出结论，相对于目前的GRACE误差预算，大气模型的不确定性不发挥突出的作用，目前的GRACE重力场解决方案的误差预算。然而，为了充分利用GRACE测量的基线精度，需要优化的去混叠。在这种情况下，GRACE重力场解对大气和海洋模型的不确定性很敏感。因此，在去混叠过程中应考虑相关的地球物理模型误差。
SUMMARY High-frequency, time-varying mass redistributions in the ocean and atmosphere have an impact on GRACE gravity field solutions due to the space–time sampling characteristics of signal and orbit. Consequently, aliasing of these signals into the GRACE observations is present and needs to be taken into account during data analysis by applying atmospheric and oceanic model data (de-aliasing). As the accuracy predicted prior to launch could not yet be achieved in the analysis of real GRACE data, the de-aliasing process and related geophysical model uncertainties are regarded as a potential error source in GRACE gravity field determination. Therefore, this study aims to improve the de-aliasing process in order to obtain a more accurate GRACE gravity field time-series. As these time-series provide estimates for the integrated mass transport in the Earth system, like the global water cycle and solid Earth geophysical processes, any increase in accuracy will lead to improvements in the geophysical interpretation of the results. So in conclusion, improving the de-aliasing is of relevance for a better understanding of geophysical processes. By no longer regarding the atmosphere and ocean model output as error-free, deeper insight into the impact of such uncertainties on the de-aliasing and on the resulting GRACE gravity field models can be obtained. For this purpose, in a first step, a full error propagation of the atmospheric and oceanic model parameters up to the de-aliasing gravity field coefficients is performed and the GRACE K-Band-Satellite-to-Satellite Tracking (KBR-SST) residuals, as an intermediate gravity field result, are analysed. The paper reviews the standard GRACE de-aliasing process and presents the mathematical model applied for the error propagation. Specifically, the effect of uncertainties in the atmospheric input parameters (temperature, surface pressure, specific humidity, geopotential) on the gravity field potential coefficients used for de-aliasing is shown in several scenarios. Finally, the impact of dealiasing products (with and without error propagation) on a GRACE gravity field solution is investigated on the level of observation residuals. From the results obtained in this study it can be concluded that with respect to the current GRACE error budget, atmospheric model uncertainties do not play a prominent role in the error budget of current GRACE gravity field solutions. Nevertheless, in order to fully exploit the GRACE measurements towards the baseline accuracy, an optimized de-aliasing is needed. In this case, GRACE gravity field solutions are sensitive to uncertainties in atmospheric and oceanic models. Thus, the associated geophysical model errors shall be taken into account in the de-aliasing process.