A 4D-Var reanalysis of FASTEX

Année de publication

2003

A complete re-analysis of the Fronts and Atlantic Storm-Track EXperiment<br> (5 January27 February 1997) is performed. It provides a reference <br>description of the life cycle of an ensemble of cyclogeneses over the <br>north Atlantic. Many aspects make this re-analysis noteworthy. In <br>particular, the FASTEX period is characterized by an exceptional <br>increase in the number of dropsoundings or radiosoundings concentrated <br>on the storm track. Another striking point of the re-analysis is the use<br> of a four-dimensional variational (4D-Var) assimilation scheme on such a<br> long period associated with the French Arpège (Action des Recherche <br>Petite Echelle et Grand Echelle) global stretched model, that allows a <br>locally high resolution in the area where dense networks of dropsondes <br>were deployed. A twin re-analysis with the same characteristics but <br>without any FASTEX data is also performed. It shows that the impact of <br>the special FASTEX data is quite noticeable in the resulting analyses <br>and is lower, but still perceptible, in the associated short-range <br>forecasts (6 h36 h). The impact of FASTEX observations on a particular <br>FASTEX case is also shown. <br>Copyright © 2003 Royal Meteorological Society</div>

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