多变量变模分解提取 GRACE 谐波系数中的条纹噪声

IF 2.8 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Guangyu Jian, Fang Zou, Chuang Xu, Zhengwen Yan
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引用次数: 0

摘要

摘要 在这项工作中,开发了一种新方法来去除重力恢复和气候实验(GRACE)任务收集的二级球谐波系数产品中的南北向条纹噪声。所提出的方法通过多变量变模分解算法从等效水高(EWH)图中提取条纹噪声。该方法的理念是提取多通道序列中经度方向的同频模式。我们方法的参数是根据经验确定的。闭环模拟研究证明,与奇异频谱分析空间(SSAS)滤波器相比,我们的方法有所改进。随后,我们使用真实的 GRACE 数据进行了空间域和频谱域研究。我们的方法只能抑制低纬度(南纬 30°∼北纬 30°)的条纹噪声,对球谐波系数的影响取决于阶次,但有可能过度平滑。同时,有据可查的水位证明,与 SSAS 过滤器相比,我们的方法进一步减少了局部质量变化时间序列中的异常值。更重要的是,用户可以降低我们方法的过滤强度,以保留小尺度的强信号,同时抑制条纹噪声。此外,还对低纬度海洋的噪声水平进行了评估。使用经验参数,我们的方法的噪声水平为 32.48 毫米 EWH,而 SSAS 和 DDK6 的噪声水平分别为 31.54 毫米和 53.52 毫米。我们的工作介绍了一种解决空间域南北条纹噪声问题的新方法。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Multivariate variational mode decomposition to extract the stripe noise in GRACE harmonic coefficients
Summary In this work, a novel method has been developed to remove the north-south stripe noise in the Level-2 spherical harmonic coefficient products collected by the Gravity Recovery and Climate Experiment (GRACE) mission. The proposed method extracts the stripe noise from the Equivalent Water Height (EWH) map via the Multivariate Variational Mode Decomposition algorithm. The idea behind our method is to extract the co-frequency mode in multiple-channel series in the longitude direction. The parameters of our method are empirically determined. The investigation in a closed-loop simulation proves the improvement of our methods compared with the Singular Spectrum Analysis Spatial (SSAS) filter. Subsequently, the spatial-domain and spectral-domain investigations are conducted by using real GRACE data. Our method only suppresses stripe noise at low latitudes (30°S∼30°N) and imposes an order-dependent impact on spherical harmonic coefficients but with potential over-smoothing. Meanwhile, the well-documented water level proves that our method further reduces outliers in a time series of localized mass variations compared with the SSAS filter. More importantly, users are allowed to reduce the filtering strength of our method to preserve small-scale strong signals while suppressing stripe noise. Moreover, noise levels over the ocean at low latitudes are evaluated as well. The noise level of our method using empirical parameters is 32.48 mm of EWH, with 31.54 and 53.52 mm for SSAS and DDK6, respectively. Our work introduces a novel method to address the issue of north-south stripe noise in the spatial domain.
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来源期刊
Geophysical Journal International
Geophysical Journal International 地学-地球化学与地球物理
CiteScore
5.40
自引率
10.70%
发文量
436
审稿时长
3.3 months
期刊介绍: Geophysical Journal International publishes top quality research papers, express letters, invited review papers and book reviews on all aspects of theoretical, computational, applied and observational geophysics.
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