Extended Abstract (408K)3.4
Data assimilation with a multiscale chemistry-transport forecast model
Blond Nadege, Laboratoire de Meteorologie Dynamique/CNRS, Palaiseau, France; and L. Bel and V. Robert
CHIMERE is a 3D eulerian chemistry-transport model covering a part of Western Europe with a resolution of about 50km. Several zooms over subregions of France permit a more detailed study of urban pollution phenomena with a resolution of about 4-6km. The model is simplified enough to allow for long simulation and real-time forecast of photoxidant pollution. With this multiscale system, a series of data assimilation processes is performed at regional and European scale. Observational ozone data are assimilated with a Statistical Interpolation method. This process is chosen for its low computer cost, unavoidable constraint for a model designed to forecast in real-time. The space isotropy and homogeneity assumptions, usually made in order to estimate error covariances, are avoided by a new scheme. Compared to simulation without assimilation using the leave-one-out method, the analysis allows a reduction of the RMS-error of 40%. A comparison of several approaches is discussed.
Since the May, 1, 2001, results of the experimental real-time forecasts of Ozone are presented on a web site (http://euler.polytechnique.fr/pioneer/). A forecast with re-initialization of the model using analysis is tested. About 200 observations are used. The improvement of the forecast due to the introduction of observational information is quantified.
Session 3, Emerging role of data assimilation in the oceans, land surface, atmospheric chemistry, hydrology, and the water cycle: Part I
Tuesday, 15 January 2002, 4:00 PM-5:30 PM
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