Adaptive observations: a feasibility study
Observations Adaptives : une étude de faisabilité
Bergot, T. ; Hello, G. ; Joly, A. ; Malardel, S.
The feasibility of the recently proposed concept of adaptive <br>observations is tested on a typical case of poorly forecast North <br>Atlantic cyclogenesis. Only numerical tools are employed, no special <br>observations. Although based on simulated data, this study addresses <br>both theoretical and practical problems of adaptive observations.In<br> the first stage of this study, the role of the data assimilation <br>processes is neutralized; the correction is done by forcing correct <br>continuous fields within the target area. These experiments prove that <br>it is necessary to correct the projection of the initial errors on the <br>first unstable plane (the first two leading singular vectors) in order <br>to significantly improve the forecast. These results also clearly <br>demonstrate that the quality of the initial conditions on a limited, but<br> quite large, area could be a major factor influencing the forecast <br>quality. In a second stage, the focus is on <br>operational aspects. The correction is done through the assimilation of a<br> discrete set of simulated profiles using a 3DVAR analysis system. This <br>leads to studying the impact of the assimilation scheme and to testing <br>different sampling strategies. These experiments suggest that the <br>concept of adaptive observations shows great promise in situations <br>comparable to the one studied here. But the current assimilation <br>systems, such as 3DVAR, require that all the structure of the target has<br> to be well sampled to have a significant beneficial effect; sampling <br>only the extremum does not suffice.</p>
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