Impact of non-smooth observation operators on variational and sequential data assimilation for a limited-area shallow-water equation model

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題名:	Impact of non-smooth observation operators on variational and sequential data assimilation for a limited-area shallow-water equation model
作者:	吳劍鋒;Steward, J. L.;Navon, I. M.;Zupanski, M.;Karmitsa, N.
貢獻者:	地球科學學院大氣科學學系
關鍵詞:	4D-Var;Earth, ocean, space;Exact sciences and technology;External geophysics;L-BFGS;LMBM;Meteorology;MLEF;non-smooth optimization;Physics of the high neutral atmosphere
日期:	2012-01-01
上傳時間:	2026-04-21 13:34:18 (UTC+8)
出版者:	Wiley-Blackwell;Chichester, UK: John Wiley & Sons, Ltd
摘要:	摘要： AbstractWe investigate the issue of variational and sequential data assimilation with nonlinear and non‐smooth observation operators using a two‐dimensional limited‐area shallow‐water equation model and its adjoint. The performance of the four‐dimensional variational approach (4D‐Var: two dimensions plus time) compared with that of the maximum‐likelihood ensemble filter (MLEF), a hybrid ensemble/variational method, is tested in the presence of non‐smooth observation operators.Following the work of Lewis & Overton and Karmitsa, we investigate minimization of the data‐assimilation cost functional using the limited‐memory Broyden–Fletcher–Goldfarb–Shanno (L‐BFGS) quasi‐Newton algorithm originally intended for smooth optimization and the limited‐memory bundle method (LMBM) algorithm specifically designed to address large‐scale non‐smooth minimization problems.Numerical results obtained for the MLEF method show that the LMBM algorithm yields results superior to the L‐BFGS method. Results for 4D‐Var suggest that L‐BFGS performs well when the non‐smoothness is not extreme, but fails for non‐smooth functions with large Lipschitz constants. The LMBM method is found to be a suitable choice for large‐scale non‐smooth optimization, although additional work is needed to improve its numerical stability. Finally, the results and methodologies of 4D‐Var and MLEF are compared and contrasted. Copyright © 2011 Royal Meteorological Society 其他題名： Q.J.R. Meteorol. Soc 出版者： Chichester, UK: John Wiley & Sons, Ltd 出版日期： 2012-01 出處： Quarterly Journal of the Royal Meteorological Society, 2012-01, Vol.138 (663), p.323-339 資源來源： Wiley Online Library Journals 版權： Copyright © 2011 Royal Meteorological Society 版權： 2015 INIST-CNRS 識別號： ISSN: 0035-9009 識別號： EISSN: 1477-870X 識別號： DOI: 10.1002/qj.935 識別號： CODEN: QJRMAM
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