Meteo-France and Mercator Ocean contribution to the search of the AF447 wreckage
Drévillon, M. ; Greiner, E. ; Paradis, Denis ; Payan, Christophe ; Lellouche, J.-M. ; Reffray, G. ; Durand, E. ; Law-Chune, S. ; Cailleau, S.
On the night of June 1st to June 2nd 2009 at 2h10 GMT, the Air France AF447 flight from Rio to Paris disappeared in a highly variable and poorly observed part of the western tropical Atlantic Ocean. In the following days the wreckage was not located and the first debris was sighted only 5 days after the accident. From June 10th to July 10th, 2009 (period hereafter called phase 1) several ships including the "Pourquoi Pas?" (Ifremer/SHOM) have conducted acoustic researches to find the beacons. Reverse drift computations were performed by several search-and-rescue groups in the world including at Météo-France, using background ocean currents from Mercator Ocean. The drift computations were started from the debris found from June 5th to June 17th and their backward trajectory until the time of the accident was computed. The results indicated very different locations for the wreckage. All these likely locations were searched during phase 2 (from July 27th to August 17th 2009) using submarine robots. The research conditions were very difficult as the bottom of the ocean is very deep (around 4000m) in that region with a very rugged topography that can be compared to the Alps under 4000m of water. These two phases of research at sea of the AF447 wreckage were both unsuccessful. The "Bureau d'Enquêtes et d'Analyses pour la sécurité de l'aviation civile" (BEA) (for the investigation of airplane accidents) decided in November 2009 to gather a group of ocean scientists and mathematicians in order to prepare the third phase of research. They had to apply new methods to reduce uncertainties in the drift computations and propose a region to begin phase 3. The latter was to start in February 2010 and finally took place from April 2nd to May 24th, 2010. The task of reducing uncertainties was challenging as very little environmental information was available at the time. Moreover the study had to be performed within a short delay (3 months) and only a few more observations were made available during this period. Ollitrault et al. (2010) present in detail the work that was done by the group of scientist hereafter called the "drift committee". The study performed by Mercator Océan and Météo-France as part of this group is described in Drévillon et al. (2012), and includes the operation of an ensemble of numerical experiments to calculate the probability of presence of the wreckage. In this article, we focus on the modelling part of the common contribution of Météo-France and Mercator Ocean as an attempt to improve the currents and winds and consequently the drift accuracy.
The common Mercator Océan and Météo-France strategy is outlined in section 2. The numerical experiments that were performed for this study are introduced in section 3. In section 4 we analyse the improvements obtained. A conclusion is drawn in section 5.
Accès à la notice sur le site du portail documentaire de Météo-France