Covariance Modeling by Means of Eigenfunctions of Laplace Operator

0457014 - ÚI 2016 RIV US eng C - Konferenční příspěvek (zahraniční konf.)
Turčičová, Marie - Mandel, Jan - Eben, Kryštof
Covariance Modeling by Means of Eigenfunctions of Laplace Operator.
JSM 2015 Proceedings. Alexandria: ASA, 2015, s. 3454-3461. ISBN 978-0-9839375-5-5.
[JSM 2015. Seattle (US), 08.08.2015-13.08.2015]
Grant CEP: GA ČR GA13-34856S
Grant ostatní: NSF(US) DMS-1216481
Institucionální podpora: RVO:67985807
Klíčová slova: data assimilation * discrete Fourier transform * spectral * diagonal covariance * maximum likelihood
Kód oboru RIV: BB - Aplikovaná statistika, operační výzkum

Large dimension of both state vector and data is a well-known challenge in environmental modeling (e.g., numerical weather forecast) and, in particular, in data assimilation. The Ensemble Kalman Filter addresses this problem by estimating the current system state and its uncertainty via their sample counterparts. However, sample covariance matrix based on a small ensemble is not a sufficiently good estimate of the true covariance. In this paper, we deal with techniques relying on transformation of the state to the spectral space and assuming a particular covariance structure based on the Laplace operator. Parameters, which this special structure depends on, are estimated by a least squares method and a maximum likelihood method. The behavior of both estimators is illustrated by a simulation. Both methods have a smaller error in Frobenius norm than the sample covariance, moreover, the latter method performs better than the former one, which corresponds to its stronger assumptions.
Trvalý link: http://hdl.handle.net/11104/0257464