The comparison was
performed separately for molecular, aerosol and mixed (molecular +
aerosol) atmospheres. For a molecular atmosphere, TOA
(top-of-atmosphere) reflectances produced by the RT codes were compared
to Coulson's tabulated values. In two other cases, the 6SV1
simulations were compared to those produced by the Monte Carlo code
and then used as benchmarks for other codes.
(please double click on each item with an asterisk to
see or hide the contents)
1. Molecular atmosphere
Conditions of the comparison
(6SV1, RT3, MODTRAN, & SHARM vs.
Coulson's)*
Table 1.
Conditions of the comparison for a pure molecular atmosphere.
Optical
thickness
t
= 0.1 (l
= 530 nm)
t
= 0.25
(l
= 440 nm)
t
= 0.5 (l
= 360 nm)
Ground
reflectance
r
= 0.0
r
= 0.25
r
= 0.0
r
= 0.25
r
= 0.0
r
= 0.25
SZA
23.0739
53.1301
78.4630
0.0
36.8699
66.4218
0.0
36.8699
66.4218
23.0739
53.1301
78.4630
23.0739
53.1301
78.4630
0.0
36.8699
66.4218
AZ
0.0; 90.0; 180
VZA
as in
Coulson-s tables (see the Excel file)
Here SZA denotes the solar zenith angle, VZA is the view
zenith angle, and AZ is the relative azimuth.
The relative differences between the simulations of each
code and Coulson's values are calculated as
|Coulson-Code|*100%/Coulson.
Results of the
comparison (6SV1, RT3,
MODTRAN, & SHARM vs. Coulson's)*
Figure 1.
Some results of the comparison with Coulson's tabulated
values for a molecular atmosphere.
Download
the Excel file
with the results. An Excel
file with VPD results is available by request.
(Note:
VPD was dropped from
the comparison after the completion of the molecular case.)
Conditions of the comparison
(6SV1 vs. Monte Carlo)*
Figure 2.
Results of the comparison of 6SV1 and Monte Carlo for a
pure molecular atmosphere.
Instead
of calculating an exact value of TOA reflectance for a given
geometric configuration, Monte Carlo calculates the average
value of all TOA reflectances confined within a given solid
angle. The hemispherical space at the top of atmosphere is
divided into a number of solid angles, specified by VZA and
AZ values. In this case, the angular sampling for the
relative AZ space (0- - 180-) is 22.5-. The sampling for VZA
space (0- - 90-) is shown in Figure 2. The boundary VZA
values are presented as angular coordinates. The relative
difference varies as the radius coordinate from 0 to 0.4%.
A special integration method was applied to match the
outputs of 6SV1 and Monte Carlo.
Results of the comparison
(RT3, MODTRAN, & SHARM vs. 6SV1)*
(Note:
In addition to the Excel files with the results, we also
provide 6SV1 Mie-files with the calculated phase function values
(251 Gaussian angles) for each value of optical thickness.)
Figure 3. Some results of the comparison of RT3,
MODTRAN, and SHARM for the UI aerosol model.
Conditions of the comparison
(6SV1 vs. Monte Carlo)*
UI: l
= 412 nm,
taer =
{0.2; 0.8}, SZA = {0.0-; 23.0-; 50.0-}, 2 x 1010
photons
AF:
l
= 670 nm,
taer =
{0.2; 0.8}, SZA = {0.0-; 23.0-; 50.0-}, 2 x 1010
photons
AS:
l
= 440 nm,
taer =
{0.2; 0.8}, SZA = {0.0-; 23.0-; 50.0-}, 2 x 1010
photons
Results of the comparison
(6SV1 vs. Monte Carlo)*
Figure 4.
The results of the comparison of 6SV1 and Monte Carlo
for the UI aerosol model.
The
MC geometric configuration is explained in captions for
Fig. 2 (Double-click on 'Results of the comparison (6SV1
vs. Monte Carlo)' in the 'Molecular atmosphere' section.
Conditions of the comparison
(RT3, MODTRAN, & SHARM vs. 6SV1)*
To
create a mixed atmosphere, a molecular US62 atmosphere was
added to each aerosol model. The molecular optical thickness
depended on the wavelength:
l
= 412 nm,
tmol
= 0.30319;
l
= 440 nm,
tmol
= 0.2322;
l
= 670 nm,
tmol
= 0.04172.
The aerosol profile
was exponential with the scale height of 2 m for all codes
except MODTRAN. The molecular profile was exponential with
the scale height of approximately 8 m. The surface was
simulated as Lambertian with the reflectancersurf
= {0.0; 0.05}.
Results of the comparison
(RT3, MODTRAN, & SHARM vs. 6SV1)*
(Note:
)
Figure 5. Some results of the comparison of RT3,
MODTRAN, and SHARM for a mixed atmosphere with the AS
aerosol constituent, bounded by black surface.
Files are organized depending on the aerosol
constituent:
Conditions of the comparison
(6SV1 vs. Monte Carlo)*
To
create a mixed atmosphere, a molecular US62 atmosphere
was added to each aerosol model. The molecular optical
thickness depended on the wavelength:
l
= 412 nm,
tmol
= 0.30319;
l
= 440 nm,
tmol
= 0.2322;
l
= 670 nm,
tmol
= 0.04172.
The aerosol
profile was exponential with the scale height of 2 m for
all codes except MODTRAN. The molecular profile was
exponential with the scale height of approximately 8 m.
Only black surface cases were simulated for this part of
the comparison.
Results of the comparison
(6SV1 vs. Monte Carlo)*
Figure 6.
Results of the comparison of 6SV1 and Monte Carlo for a
mixed atmosphere with the AS aerosol constituent.
The
MC geometric configuration is explained in captions for
Fig. 2 (Double-click on 'Results of the comparison (6SV1
vs. Monte Carlo)' in the 'Molecular atmosphere' section.
