International audienceSystème d'analyse fournissant des renseignements atmosphériques à la neige (SAFRAN) is a mesoscale atmospheric analysis system for surface variables. It produces an analysis at the hourly time step using ground data observations. One of SAFRAN's main features is that it is based on climatically homogeneous zones and is able to take vertical variations into account. Originally intended for mountainous areas, it was later extended to cover France. This paper focuses on the validation of the extended version. The principle of the analysis is described and its quality was tested for five parameters (air temperature, humidity, wind speed, rainfall, and incoming radiation), using Météo-France's observation network and data of some well-instrumented stations. Moreover, SAFRAN's rainfall was compared with another analysis, known as analyse utilisant le relief pour l'hydrométéorologie (Aurelhy). Last, two different versions of SAFRAN were compared for mountain conditions. Temperature and relative humidity were well reproduced, presenting no bias. Wind speed was also well reproduced; however, its bias was - 0.3 m s–1. The interpolation from the 6-h time step of the analysis to the 1h time step was one of the sources of error. The precipitation analysis was robust and not biased; its root-mean-square error was 2.4 mm day-1. This error was mainly due to the spatial heterogeneity of the precipitation within the geographical zones of analysis (1000 km2). The analysis of incoming solar radiation presented some biases, especially in coastal areas. The results of the comparison with some well-instrumented sites were encouraging. SAFRAN is being run operationally at Météo-France on a real-time basis for various applications

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Résumé

Disposer de longues séries de mesures d'insolation exploitables nécessite au préalable un effort de recherche de données anciennes, puis de numérisation. Dix-huit séries ont été homogénéisées sur la période 1931-2000. Ces séries viennent enrichir le jeu de diagnostics sur le changement climatique à l'échelle du territoire, confortent une partie des résultats établis pour les températures et offrent de nouvelles pistes d'analyse des mécanismes d'évolution du climat.