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An overview of the variational assimilation in the ALADIN/France numerical weather‐prediction system
Author(s) -
Fischer Claude,
Montmerle Thibaut,
Berre Loïk,
Auger Ludovic,
ŞTEFĂNESCU Simona Ecaterina
Publication year - 2005
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 - 10.1256/qj.05.115
Subject(s) - data assimilation , mesoscale meteorology , suite , numerical weather prediction , robustness (evolution) , computer science , precipitation , meteorology , quantitative precipitation forecast , covariance , assimilation (phonology) , north american mesoscale model , environmental science , weather research and forecasting model , weather prediction , climatology , mathematics , statistics , global forecast system , geography , geology , linguistics , biochemistry , chemistry , philosophy , archaeology , gene
We present an overview of the 3D‐Var data assimilation in the framework of the ALADIN/France model. The purpose of this system is to provide improved precipitation forecasts at mesoscale and in the short range, up to 18 hours. The goal of the paper is threefold. Firstly, we present initial considerations for the design of the 3D‐Var system. Secondly, we discuss in more detail the specification of the background‐error covariance matrix, by comparing three different error simulation techniques, namely two variants of the NMC method and an ensemble‐based approach. The formal, diagnostic and impact studies have led to the selection of the ensemblebased covariances for the ALADIN/France assimilation. Thirdly, scores of quantitative precipitation forecasts are shown in order to illustrate the robustness and the preliminary meteorological performance of the ALADIN/France assimilation suite. The results indicate that the tested configuration improves some aspects of the precipitation forecast, while being neutral for others, when compared with the spin‐up model. We conclude the paper by providing a more explicit insight into the future evolution of limited‐area variational analysis towards convective‐scale data assimilation. Copyright © 2005 Royal Meteorological Society