VIIRS Suspended Matter ATBD - Nasa

D43315_D
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where V is the visibility in kilometers and C is the smoke concentration in g/m 3 . This
approximate expression is accurate to about 50% and needs to be refined. The visibility is
horizontal visibility and VIIRS is responding to vertical visibility, so there probably will be no
one expression that is always applicable due to the complex structure associated with smoke
plumes.
Visibility can also be related to aerosol optical thickness. From Iqbal (1983) the relationship for
low visibilities can be written as:
V = 3.9449 / (/0.55 - 0.08498) (2)
where and are the Angstrom coefficients, V is the visibility in kilometers, and 0.55 is the
wavelength at which visibility is measured, namely 0.55 microns (or 550nm).
The previous expression can be written in terms of the aerosol optical thickness at 550 nm (550)
as follows:
V = 3.9449 / (550 – 0.08498) (3)
The first and third equations above can be combined to give the smoke concentration C as
follows:
C = 253.5 550 –21.5 (4)
A plot of this relationship is shown in Figure 10:
Smoke Concentration (ug/m^3)
1800
1600
1400
1200
1000
800
600
400
200
Smoke Concentration vs AOT at 550 nm
0
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0
AOT at 550 nm
Figure 2. Smoke concentration (g/m 3 ) vs aerosol optical thickness at 550 nm.