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A Wavelet based Suboptimal Kalman Filter for Assimilation of Stratospheric Chemical Tracer ObservationsA suboptimal Kalman filter system which evolves error covariances in terms of a truncated set of wavelet coefficients has been developed for the assimilation of chemical tracer observations of CH4. This scheme projects the discretized covariance propagation equations and covariance matrix onto an orthogonal set of compactly supported wavelets. Wavelet representation is localized in both location and scale, which allows for efficient representation of the inherently anisotropic structure of the error covariances. The truncation is carried out in such a way that the resolution of the error covariance is reduced only in the zonal direction, where gradients are smaller. Assimilation experiments which last 24 days, and used different degrees of truncation were carried out. These reduced the covariance size by 90, 97 and 99 % and the computational cost of covariance propagation by 80, 93 and 96 % respectively. The difference in both error covariance and the tracer field between the truncated and full systems over this period were found to be not growing in the first case, and growing relatively slowly in the later two cases. The largest errors in the tracer fields were found to occur in regions of largest zonal gradients in the constituent field. This results indicate that propagation of error covariances for a global two-dimensional data assimilation system are currently feasible. Recommendations for further reduction in computational cost are made with the goal of extending this technique to three-dimensional global assimilation systems.
Document ID
20040031503
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Tangborn, Andrew
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Auger, Ludovic
(Meteo France Toulouse,)
Date Acquired
August 21, 2013
Publication Date
January 1, 2003
Subject Category
Numerical Analysis
Meeting Information
Meeting: IUGG 2003
Location: Sapporro
Country: Japan
Start Date: June 30, 2003
End Date: July 11, 2003
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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