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Section: New Results

High resolution reconstruction of a tracer dispersion event

Participant : Marc Bocquet.

In a previous QJRMS two-part paper, new methods to reconstruct the source for an atmospheric tracer at regional scale have been developed. Specifically the Maximum Entropy on the Mean (MEM) method was extended to large (although linear) data assimilation problem. Tests using twin experiments and a limited subset of the data from the European Tracer Experiment [ETEX] were performed. Although temporal reconstruction knowing the location of the source was satisfying, a full 3D reconstruction was still out of reach with real data. In this work, using the MEM method and some of its refinements, a reconstruction using all ETEX-I measurements at a resolution of 1.125° x 1.125° x 1 hour is shown to be possible. This allows for a reconstruction of the full dispersion event. The MEM retrieval of the tracer plume using what is believed to be a good prior is then compared to other priors including Gaussian ones. Eventually, a reconstruction using all data sequentially in time (not all together) is obtained. This helps define what a maximum entropy filter applied to sequential data assimilation of a linear tracer should be able to do, with a view to an efficient emergency response in case of an accidental release of pollutant.


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