Quantitative Remote Sensing of African Dust Transport to the Mediterranean
Résumé
We present here an overview of our quantitative studies of African dust transport to the Mediterranean, based on Meteosat and CZCS spaceborne images of the reflected sunlight, and coincident exogeneous meteorological and chemical atmospheric or marine data. Investigations include the retrieval of the desert dust aerosol optical thickness and mass column density over seawater, of the dust deposition flux and its fate in surface seawater. The comparison between measured and Meteosat-derived dust deposition fluxes indicates that cloud cover limits short-term Meteosat survey, but that long-term averaged dust fluxes to seawater can be approximated from Meteosat data. Results from our analysis of multi-year series of Meteosat ISCCP-B2 data indicate a marked seasonal cycle of dust transport in the Mediterranean, with a high dust load in spring and summer, and a strong year to year variability. A case study of the apparent velocity and altitude of dust transport shows a primary transport of dust particles above the atmospheric boundary layer. Finally, a combined survey of desert aerosol and phytoplankton in summertime seems to provide a first observation of the impact of strong dust inputs on the phytoplankton growth.