The potential of infrared satellite data for the retrieval of Saharan-dust optical depth over Africa

Optical depth of Saharan dust derived from photometric measurements made during the dry season at a Sahelian site (Niamey, Republic of Niger) is compared with METEOSAT-2 radiance in the 10.5-12.5 μm channel for different times of the daily cycle. The ability of retrieving dust optical depth using the outgoing radiance of infrared atmospheric window is clearly demonstrated for the middle of the day. Results obtained with nighttime data through a relation between dust optical depth and visibility are also disussed. -from Authors