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

5.1.2 CALIPSO measurements and VFM product
The measurements of CALIPSO are free to public, from June 2006 to present. The
size of each file (version 2.01) of daytime is around 500 Mb. The data provide such
parameter as total attenuated backscatter at 532nm and 1064nm, perpendicular attenuated
backscatter, height, elevation, latitude, longitude, and so on. Table 5.2 gives the
measurable height relative to sea level. The vertical and horizontal spatial resolution
varies with the height.
In CALIPSO measurements, total attenuated backscatter at 532nm and 1064nm and
perpendicular attenuated backscatter at 532nm directly provide vertical information about
aerosols. Fig.5.1 is an example to show CALIPSO attenuated backscatter signal at
1064nm on March 30, 2007. The horizontal axis stands for the geolocation of sample
point and vertical axis represents the height relative to sea level. Usually, the value of
attenuated backscatter is from 0.0001 ~ 0.1.
Fig. 5.1 displays the CALIPSO attenuated backscattering signal at 1064 nm in the
northwest China on July 26, 2006 at the UTC time 07:30. In the figure, the red solid line
in horizontal direction is the elevation of the ground surface. A heavy aerosol (or cloud)
over Taklimakan Desert is captured by CALIPSO, floating at the height of 2 -3 km from
38.27 0 N to 40.3 0 N. Heavy clouds are floating at the height of 7 ~ 8 km in the south side
of desert and at the height of 5 km in the north side of desert.
The VFM, level-2 product of CALIPSO, reports the scene classification based on
the physical feature differences of aerosols and clouds. With the SCA (Scene
Classification Algorithm), the atmospheric features are classified as either clouds or
66