Comparisons of atmospheric data and reduction methods for the analysis of satellite gravimetry observations
Comparisons of atmospheric data and reduction methods for the analysis of satellite gravimetry observations
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DOI：
10.1002/jgrb.50160
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发表时间：
2013-05
期刊：
影响因子：
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通讯作者：
E. Forootan;O. Didova;Jürgen Kusche;A. Löcher
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文献类型：
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作者：
E. Forootan;O. Didova;Jürgen Kusche;A. Löcher
重力恢复和气候实验（GRACE）导出的重力解包含误差，主要是由于仪器噪声，各向异性空间采样和时间混叠。在设计未来卫星重力测量任务的设想方案时，讨论了通过使用更灵敏的传感器和（或）增加空间各向同性来提高卫星重力测量观测质量的问题。然而，由于背景模型的不完全简化而引起的时间混叠仍然是影响重力场解质量的一个因素。本文具体探讨了可能的物理，几何和数值修改的三维（3 D）的积分方法，以消除卫星重力测量观测的高频大气的影响。新的修改后的三维方法，然后应用于计算新的一套大气去混叠产品，使用欧洲中期天气预报中心（ECMWF）业务分析模型和ERA的中期再分析的大气场。修改的影响进行了比较，发射前的基线和当前的GRACE的误差修正曲线，以及一个Bender型多轨道卫星配置的误差修正曲线。具体地说，我们发现，使用依赖于纬度的半径，纬度和高度依赖于重力加速度沿着与数值修改有相当大的影响的三维积分。将新产品与GRACE大气和海洋去混叠级别1B的产品进行比较，显示出GRACE和可能的本德大气去混叠类型使命发射前基线的不可忽略的差异，分别高达13和50谐波度。ECMWF业务分析的去混叠产品与ERA ERAM-Interim的去混叠产品也有很大的差异，说明了输入参数对最终大气去混叠产品的重要性。
The Gravity Recovery and Climate Experiment (GRACE) derived gravity solutions contain errors mostly due to instrument noise, anisotropic spatial sampling, and temporal aliasing. Improving the quality of satellite gravimetry observations, in terms of using more sensitive sensors and/or increasing the spatial isotropy, has been discussed in the context of the designed scenarios of future satellite gravimetry missions. Temporal aliasing caused by incomplete reducing of background models, however, is still a factor that affects the quality of the gravity field solutions. This paper specifically explores the possible physical, geometrical, and numerical modifications of the three‒dimensional (3‒D) integration approach to eliminate the high‒frequency atmospheric effects from satellite gravimetry observations. The new modified 3‒D approach is then applied to compute new sets of atmospheric dealiasing products, using atmospheric fields from the European Centre for Medium‒Range Weather Forecasts (ECMWF) operational analysis model and ERA‒Interim reanalysis. Impacts of modifications are compared to the prelaunch baseline and the current error‒curve of GRACE as well as an error‒curve of a Bender‒type multiorbit satellite configuration. Specifically, we found that using latitude‒dependent radius, latitude‒ and altitude‒dependent gravity accelerations along with numerical modifications have a considerable impact on the 3‒D integral. Comparing the new products to those of GRACE Atmosphere and Ocean Dealiasing level‒1B shows a nonnegligible difference with respect to the prelaunch baseline of GRACE and a possible Bender‒type mission up to harmonic degrees 13 and 50, respectively. A big difference is also found between the derived dealiasing products from ECMWF operational analysis and ERA‒Interim indicating the importance of input parameters on the final atmospheric dealiasing products.