Short-wave and mid-infrared imagery to distinguish silicate dusts and volcanic aerosols from meteorological clouds

摘要

Silicate dusts, volcanic ash clouds and Asian dust, are well detected by the 'split-window' method, which calculates the brightness temperature difference of the 11 and 12 μm bands. Volcanic plumes containing less ash are enhanced by the difference of the visible and near infrared bands of NOAA/AVHRR data. In order to supplement these difference images and improve the discrimination of volcanic ash- rich/poor plumes and of Asian dust from various meteorological clouds, various combinations of AVHRR imagery were investigated. It was found that the differences of the 3.7 and 11 μm bands and of the 1.6 μm and visible bands are useful to distinguish between thick clouds and dusts. Colour composite images containing the 1.6 or 3.7 μm bands are useful for distinguishing the objects from any meteorological clouds, because these bands are sensitive to droplet size.