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Multiple‐truncation incremental approach for four‐dimensional variational data assimilation
Author(s) -
Veerse F.,
Thepaut J.N.
Publication year - 1998
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49712455006
Subject(s) - truncation (statistics) , data assimilation , mathematics , truncation error , mathematical optimization , barotropic fluid , computer science , algorithm , statistics , physics , meteorology , mechanics
The incremental approach provides an approximate solution to four‐dimensional variational data assimilation (4D‐Var) at a reasonable CPU cost. An extension of this approach is studied, namely the multiple‐truncation incremental technique, and is compared to the standard and single‐truncation incremental implementations of 4D‐Var, using a two‐dimensional barotropic vorticity‐equation model. The quasi‐continuous approach deals with the cut‐off problem and spreads the computer requirements over time. Quasi‐continuous incremental and quasi‐continuous multiple‐truncation incremental techniques are assessed. The same number of iterations is specified in all the experiments. The multiple‐truncation incremental technique is found to produce a good approximate analysis at a lower CPU cost. Applying the quasi‐continuous approach to the incremental methods adds some benefit in terms of computer time.