الوصف: |
EnglishAlthough the evolution of the state of the atmosphere intrinsically is to be considered as a geographically global problem, numerical weather prediction also has been, and still is, dealing with limited area models besides global ones. One important reason is the opportunity offered by limited area models to increase, sometimes drastically, the spatial resolution of the model grids, since the forecast does not have to cover the whole globe. Physical processes are then potentially represented with a higher degree of realism as well as sometimes complexity. For instance, today operational limited area models describe heavy convective events, and their modelled representation of microphysics, clouds, turbulence or the exchanges with continental and oceanic surfaces is becoming increasingly realistic. At the same time, for data assimilation, the use of fine scale observations becomes widespread, such as radar data or very high density satellite observations. In this article, a historical and scientific overview of operational limited area modelling over the last twenty years at Meteo-France is presented, addressing the two specific models Aladin and Arome. francaisL'evolution de l'etat de l'atmosphere est un probleme a apprehender a priori dans sa globalite geographique, c'est-a-dire sur tout le globe terrestre. Pour autant, la prevision numerique du temps s'appuie a la fois sur des modeles a domaine limite et des modeles a domaine global. Une raison principale a cela est la possibilite offerte en domaine limite, ou a aire limitee, a augmenter, parfois considerablement, la resolution spatiale des grilles des modeles, puisque la prevision n'a plus besoin de couvrir tout le globe. Les processus physiques sont alors a priori « vus » avec plus de realisme, mais aussi parfois davantage de complexite. Ainsi, aujourd'hui, les modeles a aire limitee operationnels representent les phenomenes convectifs intenses et gagnent toujours plus en realisme quant aux descriptions des processus de la microphysique, des nuages, de la turbulence ou des echanges avec les surfaces continentales et oceaniques. De meme, en assimilation de donnees, l'utilisation d'observations de fine echelle se generalise, comme les radars ou les observations satellitaires a tres haute densite. Nous presentons ici un tour d'horizon historique et scientifique des deux modeles a aire limitee qui ont marque le paysage operationnel de Meteo-France ces vingt dernieres annees, Aladin puis Arome. |