Determination of the wind speed threshold for the emission of desert dust using satellite remote sensing in the thermal infrared

The Infrared Difference Dust Index (IDDI), derived from images obtained from the Meteosat 10.5- to 12.5-mu m channel, describes the dust distribution over the Saharan-Sahelian region. This IDDI, associated with the 10-m wind speed reanalyses from the European Centre for Medium-Range Weather Forecasts (ECMWF), reveals whether or not the observed dust is associated with emission from an underlying source. This result allows one to determine the wind speed thresholds for dust emission from targets located in the western, central, and eastern Saharan-Sahelian region, by means of satellite remote sensing. Threshold values determined for seven targets are presented. A comparison is carried out between such values and direct determinations obtained through the description of the soil texture and surface roughness of these targets. The agreement between these quite independent determinations is conclusive, with an average difference of 0.3 m s(-1) and a rms difference of 0.35 m s(-1).