Proceedings Article | 8 November 2012
KEYWORDS: Clouds, Decision support systems, Composites, MODIS, Particles, Ocean optics, Satellites, Thermography, Water, Radiative transfer
The AVI method can detect the dust and sandstorms (DSS) in satellite images both at daytime and night. The aerosol
vapor index (AVI) is defined as AVI=T12-T11, where T12 and T11 are the brightness temperatures at 12μm and 11μm
wave lengths, respectively. The fault of AVI method is to mistake thick clouds for DSS rarely. Iino et al. (2002, 2004)
proposed the composite color images for discriminating DSS from clouds in daytime NOAA-AVHRR images. In this
paper, Terra/Aqua-MODIS data are used. First, it is explained that usual clouds bring the effect of AVI<0, and the clouds
with very large optical thickness and very large particle size may bring the effect of AVI<0, by using the BTD vs. T11
charts of Inoue (2006), where BTD=-AVI. Examples of the cloud images of AVI<0 are shown and interpreted using the
AVI vs. T11 scatter chart. Next, the views of objects (DSS, usual ice-cloud, usual water-cloud, ice-cloud with large
optical thickness, water-cloud with large optical thickness, snow field and ice, land, sea) in the single-band images
(bands 1, 3, 4, 6, 7 and T11(band31), T12(band32)) and the band-difference images (band1-band3, band4-band3, band6-
band1, band7-band1, AVI) are examined. The good composite color images which can discriminate DSS from clouds etc.
are {R,G,B=AVI, band7-band1, T11} and {R,G,B=AVI, band4-band3, T11} for daytime images, and {R,G,B=T11, AVI,
none} for nighttime images.
