Three-dimensional distribution of a major Saharan dust outbreak in June2011 derived from IASI satellite observations

International audienceThe Sahara is the world’s largest source of mineral dust in the atmosphere, which is a key player ofthe Earth system. At the regional scale, the environmental impacts of desert dust strongly depend onthe three-dimensional (3D) distribution of dust plumes resulting from long-range transport. Dustlayers can impact chemical balances, atmospheric stability or cloud properties depending on thealtitude at which they are transported. Near the surface, dust can directly affect air quality and settledown on the surface by dry deposition. The quantification of such impacts are highly uncertain,particularly due to the sporadic character of dust emissions as well as the large variability of dustproperties and occurrence linked to the meteorological controls. A better understanding of the 3Ddistribution of Saharan dust and the associated mechanisms for uplifting and redistributing it in thevertical is fundamental for quantifying its environmental impacts.This research work presents the first observation of the 3D distribution of a major Saharan dustoutbreak over the Sahara in June 2011, using new aerosol retrievals derived from IASI (InfraredAtmospheric Sounding Interferometer). For this, we use a novel auto-adaptive Tikhonov-Philips-typeapproach called AEROIASI to retrieve vertical profiles of dust extinction coefficient at 10 μm formost cloud-free IASI pixels, both over land (including bright desert surfaces) and ocean. The dustvertical distribution derived from AEROIASI is shown to agree remarkably well with along tracktransects of CALIOP space-borne lidar vertical profiles as well as with aerosol optical depth derivedfrom AERONET sun photometer measurements over West Africa. A comparison is as well madewith airborne lidar and in situ measurements over the Sahara performed in the framework of theFENNEC field campaign. We also compare AEROIASI with several satellite retrievals availableover the Sahara (e.g. MODIS-DeepBlue, OMI, SEVIRI).Using AEROIASI observations, we analyse the 3D pathways of the Saharan dust plumes as they aretransported across the Sahara. Particularly, we focus our study on the role of cold pools generated bymesoscale convective system, convective mixing in the Saharan atmospheric boundary layer andstrong Harmattan winds as mechanisms for vertically redistributing the Saharan dust plumes