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arXiv 2301.04828stat.MEcs.NAmath.NAphysics.ao-ph
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局部协方差估计:贝叶斯观点

Localized covariance estimation: A Bayesian perspective

Robert J. Webber, Matthias Morzfeld

摘要:

数值天气预报中的一个主要问题是从少量样本中估计高维协方差阵。当总体维数远大于样本数时,极大似然估计不能提供可靠的估计。幸运的是,NWP从业者已经找到了巧妙的方法,通过利用相关性随空间距离衰减的假设来提高协方差估计的准确性。在这项工作中,贝叶斯统计是用来提供一个新的理由和分析的实际数值预报协方差估计。贝叶斯框架涉及操纵对称正定矩阵上的分布,它导致两个主要发现:(i)协方差阵的常用“混合估计量”具有自然的贝叶斯解释;(ii)非常常用的“舒尔乘积估计量”不是贝叶斯的,但它可以在贝叶斯框架内进行研究和理解。作为实际意义,贝叶斯框架显示了如何减少协方差估计所需的调整量,它表明有效的协方差估计应该植根于理解和惩罚条件相关性,而不是相关性。

英文摘要:

A major problem in numerical weather prediction (NWP) is the estimation of high-dimensional covariance matrices from a small number of samples. Maximum likelihood estimators cannot provide reliable estimates when the overall dimension is much larger than the number of samples. Fortunately, NWP practitioners have found ingenious ways to boost the accuracy of their covariance estimators by leveraging the assumption that the correlations decay with spatial distance. In this work, Bayesian statistics is used to provide a new justification and analysis of the practical NWP covariance estimators. The Bayesian framework involves manipulating distributions over symmetric positive definite matrices, and it leads to two main findings: (i) the commonly used "hybrid estimator" for the covariance matrix has a naturally Bayesian interpretation; (ii) the very commonly used "Schur product estimator" is not Bayesian, but it can be studied and understood within the Bayesian framework. As practical implications, the Bayesian framework shows how to reduce the amount of tuning required for covariance estimation, and it suggests that efficient covariance estimation should be rooted in understanding and penalizing conditional correlations, rather than correlations.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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