Collaborative Research: Localized Analysis of Geophysical Signals Acquired by Satellites: Making the most of GRACE

合作研究：卫星获取的地球物理信号的本地化分析：充分利用 GRACE

• 批准号: 1013333
• 负责人: C. K. Shum
• 金额: $ 11万
• 依托单位: Ohio State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-15 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1013333&HistoricalAwards=false
• 关键词: Collaborative; Research; Localized; Analysis; Geophysical

Almost every geophysical process leaves it signature in the terrestrial gravity field or its changes. If the process is "big'' enough, it can be measured by GRACE, a twin satellite mission that is sensitive to the Earth's time-variable gravity field, which has been yielding data for about seven years now. Among its many other accomplishments, models based on GRACE have provided evidence that the Earth's polar regions are losing mass due to progressive melting of their ice cover, and GRACE modeling has also helped constrain crustal deformation resulting from large earthquakes, thereby inaugurating an era of a new class of earthquake observations. The GRACE data are noisy and require extensive processing, filtering, and statistical analysis to yield signals of this kind, which are buried deeply beneath the noise and contaminated by the geophysical signatures of ocean currents, the hydrological cycle, or post-glacial rebound. Our methods development will enable us, and the scientific community, to make the most of today's available GRACE data. Well-constrained mass flux rates from Earth's polar regions, and their errors, and the robust detection, analysis and modeling of the coseismic deformation from large earthquakes will stand alone as scientific results, but they will also feed back into climate research, glaciology, seismology, and geodesy. Even more broadly than that, the problems we solve are relevant in providing new estimation methods for noisy and incomplete data distributed on a sphere, in the most general sense, e.g. as used in biomedical and statistical research, in physics, cosmology and computer science.We develop a new mathematical technique for the inversion of GRACE data, which are noisy and incomplete. Central to this effort is the development of "noise-cognizant Slepian functions'', a function basis, alternative to spherical harmonics, that is eminently suited to represent and analyze geographically localized, bandlimited, signals on the sphere. No longer producing only spatial averages of the signal, nor reprocessing global models based on spherical harmonics, we perform inversions on time series of the inter-satellite potential difference derived from GRACE, directly in this basis. From this we recover estimates of the entire spatial dependence of the mass gain/loss in ice-covered regions and hydrological basins, as well as estimates of the gravity perturbations accompanying large earthquakes. The former are important to science and society per se, the latter add information on a different temporal and spatial scale to that which can be had from GPS measurements or seismological data.This project is supported by the Geophysics, Arctic Natural Sciences, and Antarctic Earth Sciences Programs.

几乎每一个地球物理过程都会在地球重力场或其变化中留下自己的印记。如果这个过程足够“大”，就可以用GRACE来测量。GRACE是一个对地球随时间变化的重力场很敏感的双卫星任务，它已经产生了大约7年的数据。在许多其他成就中，基于GRACE的模型提供的证据表明，由于冰盖的逐渐融化，地球的极地地区正在失去质量，GRACE模型还有助于抑制大地震引起的地壳变形，从而开创了一个新的地震观测时代。GRACE的数据是有噪声的，需要大量的处理、过滤和统计分析才能产生这样的信号，这些信号深埋在噪声之下，受到洋流、水文循环或冰川后反弹的地球物理特征的污染。我们的方法开发将使我们和科学界能够充分利用今天可用的GRACE数据。来自地球极地地区的质量通量率及其误差，以及对大地震同震形变的可靠检测、分析和建模，将作为科学成果单独存在，但它们也将反馈到气候研究、冰川学、地震学和大地测量学中。甚至更广泛地说，我们解决的问题与提供新的估计方法有关，这些方法在最一般的意义上分布在一个球体上的有噪声和不完整的数据，例如用于生物医学和统计研究，物理学，宇宙学和计算机科学。我们提出了一种新的数学方法来反演具有噪声和不完整的GRACE数据。这项工作的核心是开发“噪声识别Slepian函数”，这是一种函数基础，可替代球面谐波，非常适合表示和分析地理上本地化，带宽有限的球体信号。我们不再只生成信号的空间平均值，也不再对基于球面谐波的全球模型进行再处理，而是直接在此基础上对GRACE导出的卫星间电位差的时间序列进行反演。由此，我们恢复了冰覆盖地区和水文盆地质量增益/损失的整个空间依赖性的估计值，以及伴随大地震的重力扰动估计值。前者对科学和社会本身都很重要，后者在不同的时间和空间尺度上增加了GPS测量或地震数据所能获得的信息。本项目由地球物理、北极自然科学和南极地球科学项目资助。