A strategy for producing refined currents in the Equatorial Atlantic in the context of the search of the AF447 wreckage

Abstract

On the night of 1st June 2009, a Rio-Paris Air France flight (AF447) disappeared in a highly variable and poorly observed part of the western tropical Atlantic Ocean. The first debris was located 5 days after the accident. Several reverse drift computations were conducted in order to define the likely position of the wreckage. Unfortunately, the performance of the operational ocean analyses available in the region of interest ranges from 80 to 100 km of positioning error after 5 days of inverse drift computation. In preparation of the third phase of research of the wreckage at sea, a series of numerical experiments was performed at Météo-France and Mercator Océan in an attempt to better compute the surface currents in the region and for the period of the accident of the AF447 (May and June 2009). Tailored high-resolution atmosphere and ocean reanalyses were first produced respectively at Météo-France and Mercator Océan. Several nested experiments were then performed with a small and flexible ocean model limited to the region of interest. The date of the initial conditions and the type of atmospheric forcing fields were varied in order to produce a small ensemble from which information on the sensitivity to these changes could be derived. Probabilistic and statistical combinations between model and observations were tested and a solution was finally selected by means of a comparison of drift computations with independent surface drift observations.

Estimates of surface drifter trajectories in the equatorial Atlantic: a multi-model ensemble approach

“…The airplane disappeared on June 1st 2009 near 3 • N and 31 • W, and a large international effort was organized to try to find the wreckage. The contribution of oceanographers is described in (Ollitrault 2010) and part of it in Drévillon et al (2012). This region is very challenging for ocean models because of tropical waves and especially for SURCOUF because of the breakdown in geostrophic balance at the equator.…”

Personal recommendation system for foraging

“…The corresponding probability of other area r is updated to 1 ' 1 r r r pq = > − (There is in a similar way) As for after search some primary simulating point (1,1), calculate primary joint probability p0 is 0.2883. After search, the probability of this point is updated to:…”

Status and future of global and regional ocean prediction systems

“…An improved process for taking into account available observations in the assimilation scheme will also be developed thanks to a tuning of the observation errors based on Desroziers criteria (Desroziers et al 2005) and with an optimization of the assimilation window to improve the initial state and consequently the forecast. Previous studies have shown improvements in forecasting with a shorter assimilation window from 7 to 5 days, for example (Drévillon et al 2013), or with a time window depending on the type of observation . From a more long-term perspective, the horizontal and vertical resolution will be improved, and the assimilation scheme will be updated to take into account satellite ocean colour observations, which are already available in real time with a good global coverage and a high resolution.…”

“…The IBI system was developed in 2011 in the context of the EU-founded project MyOcean in collaboration with Puertos del Estado (Spain). This system is characterized not only by the inclusion of the tidal signal in the OGCM (NEMO) model but also by an improved mixed layer scheme (Dombrowsky et al 2012).…”