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The impact of desert aerosols on climate, atmospheric processes, andthe environment is still debated in the scientific community. The extent oftheir influence remains to be determined and particularly requires a betterunderstanding of the variability of their distribution. In this work, westudied the variability of these aerosols in western Africa using differenttypes of satellite observations. SeaWiFS (Sea-Viewing Wide Field-of-ViewSensor) and OMI (Ozone Monitoring Instrument) data have been used tocharacterize the spatial distribution of mineral aerosols from their opticaland physical properties over the period 2005–2010. In particular, we focusedon the variability of the transition between continental western African andthe eastern Atlantic Ocean. Data provided by the lidar scrolling CALIOP(Cloud-Aerosol Lidar with Orthogonal Polarization) onboard the satelliteCALIPSO (Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations)for the period 2007–2013 were then used to assess the seasonal variabilityof the vertical distribution of desert aerosols. We first obtained a goodrepresentation of aerosol optical depth (AOD) and single-scattering albedo(SSA) from the satellites SeaWiFS and OMI, respectively, in comparison with AERONETestimates, both above the continent and the ocean. Dust occurrence frequencyis higher in spring and boreal summer. In spring, the highest occurrences arelocated between the surface and 3 km above sea level, while in summer thehighest occurrences are between 2 and 5 km altitude. The verticaldistribution given by CALIOP also highlights an abrupt change at the coastfrom spring to fall with a layer of desert aerosols confined in anatmospheric layer uplifted from the surface of the ocean. This uplift of theaerosol layer above the ocean contrasts with the winter season during whichmineral aerosols are confined in the atmospheric boundary layer. Radiosondesat Dakar Weather Station (17.5° W, 14.74° N) provide basicthermodynamic variables which partially give a causal relationship between thelayering of the atmospheric circulation over western Africa and their aerosolcontents throughout the year. A SSA increase is observed in winter and springat the transition between the continent and the ocean. The analysis of meanNCEP (National Centers for Environmental Prediction) winds at 925 hPa between2000 and 2012 suggest a significant contribution of coastal sand sources fromMauritania in winter which would increase SSA over the ocean

Seasonal cycle of desert aerosols in western Africa: analysis of the coastal transition with passive and active sensors