i Detection of Smoke and Dust Aerosols Using Multi-sensor Satellite ...

The dust has a high reflectivity at band 7 but a low reflectivity at band 3 (blue band).
Contrarily, blue band is sensitive to cloud but band 7 is insensitive to cloud. This inverse
spectral feature helps greatly for distinguishing dust and cloud. Qu et al. (2006) raised
NDDI to detect dust, with the formula NDDI = (R3 − R7) / (R3 + R7).
The BTD (3.7, 11) is selected to separate dust from surface scenes. Both dust and
surface scenes have a similar BT at the band 20 (3.7μm) but dust has much lower BT at
the LWIR than surface scenes. Among bands in LWIR, the BTD of band 31 (11μm)
relative to band 20 has the largest statistical difference between dust and surface scenes.
Moreover, in reflective solar spectrum the relative large reflectance difference
between dust and surface scenes (both bright and dark surfaces) is found at band 1.
Therefore, the single reflectance of band 1 is picked up to differentiate dust from surface
scenes.
Overall, the BTD (12, 11) and NDDI are chosen for discriminating dust and cloud,
while BTD (3.7, 11) and the single reflectance of band 1 are chosen for identify dust over
both dark and bright surfaces. In each branch, both RSBs and TEBs are used.
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