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

After spatial registration, the overlapped areas (namely over CALIPSO path) can be
divided into two categories according to MODIS BTD (12, 11) values: BTD (12, 11) > 0
and BTD (12, 11) < 0. The comparison between measurements of two sensors is
performed. If a layer is labeled as cloud in CALIPSO VFM product but it located in the
area having positive BTD (12, 11μm) values, it is identified as dust aerosol.
5.2.2 Results
The same region is also observed by Aqua MODIS and shown with MODIS true
color image in Fig. 5.4(a). The image is generated with measurements extracted from two
swaths at UTC time 7:25 and 7:30. The dust aerosol is located at the eastern desert. The
blue dash line is the footprint of CALIPSO in this area. It is clear that CALIPSO passes
cross the dust aerosol. The BTD (12, 11μm) values of the same region is given in Fig.
5.4(b). And the BTD (12, 11μm) values over the CALIPSO footprint is given in Fig. 5.3.
Obviously, the BTD (12, 11μm) values is larger than zero in the area having the latitude
from 36.75 0 N - 40.80 0 N, which means dust aerosol is dominated in this area. Therefore,
the dust aerosol in that area is identified and marked with dark circle in Fig. 5.2.
Fig. 5.5 gives the MODIS true color image of another case in which the dust aerosol
aroused in the northeast China on March 30, 2007. The footprint of CALIPSO is plotted
in blue dash line from equator to North Pole. The corresponding measurements of images
are extracted partly from two MODIS swaths at the UTC time 05:55 and 06:00. The
MODIS BTD (12, 11μm) image is plotted in Fig. 5.5(b) and corresponding BTD (12,
11μm) over CALIPSO footprint is given in Fig. 5.6. The CALIPSO is just passing
through this dust storm. From MODIS true color image, the dust aerosol is overlapped
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