Three-dimensional distribution of a major Saharan dust outbreak in June 2011 derived from IASI satellite observations

Abstract : The daily evolution of the three-dimensional (3D) structure of a major Sahran dust outbreak over the Sahara is observed from space for the first time, using new aerosol retrievals derived from IASI (Infrared Atmospheric Sounding Interferometer). This dust event was initiated by a suite of cold-pools generated by mesocale convective systems over West Africa in June 2011. We have used a novel auto-adaptive Tikhonov-Philips-type approach called AEROIASI to retrieve vertical profiles of dust extinction coefficient at 10 μm for most cloud-free IASI pixels, both over land (including bright desert surfaces) and ocean. The dust vertical distribution derived from AEROIASI is shown to agree remarkably well with along-track transects of CALIOP space-borne lidar vertical profiles as well as with aerosol optical depth derived from AERONET sun photometer measurements over West Africa. A comparison is as well made with airbone lidar and in situ measurements over the Sahara performed in the framework of the FENNEC field campaign. We also compare AEROIASI with several satellite retrievals available over the Sahara (MODIS-Deepblue, OMI, SEVIRI). AEROIASI allows the daily characterization of the 3D transport pathways of a major dust plumes across the Sahara. We focus our study on the role of the mesoscale atmospheric circulation over the Sahara and the Saharan atmospheric boundary layer on the 3D distribution of Saharan dust.