and Physics Saharan dust infrared optical depth and altitude retrieved from AIRS: a focus over North Atlantic – comparison to MODIS and

Abstract. Monthly mean infrared (10 µm) dust layer aerosol optical depth (AOD) and mean altitude are simultaneously retrieved over the tropics (30 ◦ S–30 ◦ N) from almost seven years of Atmospheric Infrared Sounder (AIRS) observations covering the period January 2003 to September 2009. The method developed relies on the construction of look-up-tables computed for a large selection of atmospheric situa-tions and follows two main steps: first, determination of the observed atmospheric thermodynamic situation and, second, determination of the dust properties. A very good agree-ment is found between AIRS-retrieved AODs and visible op-tical depths from the Moderate resolution Imaging Spectro-radiometer (MODIS/Aqua) during the main (summer) dust season, in particular for three regions of the tropical North Atlantic and one region of the north-western Indian Ocean