![Page 1: Experimental validation of the MODTRAN 5.3 sea surface ...Experimental validation of the MODTRAN 5.3 sea surface radiance model Denis Dion, Vincent Ross* and Daniel St-Germain 33rd](https://reader036.vdocument.in/reader036/viewer/2022071420/61199c7f8d984d730241378f/html5/thumbnails/1.jpg)
Experimental validation of the MODTRAN 5.3 sea surface radiance model
Denis Dion, Vincent Ross* andDaniel St-Germain
33rd Review of Atmospheric Transmission Models Meeting
June 2011
* With AEREX Avionic Inc
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Contents
• Introduction
• The sea surface BRDF model
• Complementary models
• The MIRAMER campaign
• Experimental and modeling uncertainties
• Experimental Results
• Conclusions
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Introduction
Complexity of sea surface radiance– Background
• Thermal emissions• Direct solar reflections• Indirect solar reflections
– Foreground• Contributes to atmospheric radiance
Radiative coupling
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Introduction
A sea surface BRDF for greater radiance accuracy
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Situation with MODTRAN
• No full BRDF coupling up to MODTRAN 4• No sea surface BRDF up to MODTRAN 5 v2• Basic aerosol models, limited user inputs• Shortcomings in refracted path at horizon ranges in
MODTRAN 4
• MODTRAN 5 v3– Fully coupled analytical sea surface BRDF– SAP (Spectral Aerosol Profile) input– Refracted path input
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The sea surface BRDF
( ) ( )[ ]3
, ( ) ( , ) ( , ),
4 ( ) 1 ( ) ( ) cos coss r r r
s rn n r r s r s
r p W Hf
z v vζπ
θ θ=
⋅ + Λ + Λψ ψ ζ ζ Ψ ζ Ψ
ψ ψU U
Ross, V., D. Dion, and G. Potvin, “Detailed analytical approach to the Gaussian surface bidirectional reflectance distribution function specular component applied to the sea surface,” J. Opt. Soc. Am. A Opt. Image Sci., 22, 2442– 2453 (2005).
Fresnel reflectance
Probability of specular reflection
Wave facet angle weighing
Wave facet hiding
Bistatic wave shadowing
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Coupling to MODTRAN
• BRDF is coded in FORTRAN in MODTRAN 5
• Fourier moments are computed– Input in DISORT
• DISORT multiple scattering uses BRDF as a lower boundary condition
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Other modeling considerations
• Marine aerosols are computed using MEDEX– Well suited for the Mediterranean– Input in MODTRAN using the SAP input
• MBL (marine boundary layer) thermodynamic profiles are computed using the DRDC modules– Monin-Obukhov similarity theory
• Refracted optical paths are used as input
• Sea surface statistical properties: Elfouhaily et al.– Fetch, atmospheric stability
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The MIRAMER campaign (May 2008)• Cedip Jade (Flir ATS) cameras on board
the Atalante ship– 3.4 – 5.5 mm (3.93 – 4.14 mm filter for glint)– 8.19 – 8.96 mm
• Environmental characterization– Radiosondes (2-3 day)– Local meteorological measurements
• Air and sea temperature• Wind speed/direction• Relative humidity
– Visibility meter (aerosols)– Aeronet station nearby (Toulon)– Solar pyranometer (solar irradiance)
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• Experimental– Image calibration and limited dynamic range
• Can reach 20% but probably lower (4-5%)– Horizontal variations (temperature, etc.) not measured
• Temperature +/- 1o
– Wind gusts– Bulk vs. skin temperature
• +/- 1o
• Modeling– Slope statistics values
• 80% between models– Aerosol modeling– Multiple reflections– Cirrus clouds
Experimental and modeling uncertainties
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Results• Non glint
– Midwave
– Longwave
-7 -6 -5 -4 -3 -2 -1 02.15
2.2
2.25
2.3
Rad
ianc
e (W
/m2 /s
ter)
ATAL 95 (1159) BII
-7 -6 -5 -4 -3 -2 -1 0-2
-1
0
1
Diff
eren
ce (%
)
Elevation (degrees)
12.5
13
13.5
14
14.5
15
App
aren
t tem
pera
ture
(o C)
Measurment
Simulation (-0.227 W/m2/ster)
σerr = 0.56%
-7 -6 -5 -4 -3 -2 -1 02.3
2.35
2.4
2.45
Rad
ianc
e (W
/m2 /s
ter)
ATAL 109 (1267) BII
-7 -6 -5 -4 -3 -2 -1 0-2
0
2
Diff
eren
ce (%
)
Elevation (degrees)
14.5
15
15.5
16
16.5
17
App
aren
t tem
pera
ture
(o C)
Measurment
Simulation (-0.099 W/m2/ster)
σerr = 0.76%
-7 -6 -5 -4 -3 -2 -1 04
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
Rad
ianc
e (W
/m2 /s
ter)
ATAL 89 (1116) BIII
-7 -6 -5 -4 -3 -2 -1 0-2
0
2
4
Diff
eren
ce (%
)
Elevation (degrees)
-10
-5
0
5
App
aren
t tem
pera
ture
(o C)
Measurment
Simulation (-1.39 W/m2/ster)
σerr = 1.76%
-7 -6 -5 -4 -3 -2 -1 05.5
5.6
5.7
5.8
5.9
6
6.1
Rad
ianc
e (W
/m2 /s
ter)
ATAL 107 (1255) BIII
-7 -6 -5 -4 -3 -2 -1 0-2
0
2
Diff
eren
ce (%
)
Elevation (degrees)
4
6
8
10
12
14
16
18
20
App
aren
t tem
pera
ture
(o C)
Measurment
Simulation (-0.133 W/m2/ster)
σerr = 1.14%
-7 -6 -5 -4 -3 -2 -1 05.9
6
6.1
6.2
6.3
6.4
Rad
ianc
e (W
/m2 /s
ter)
ATAL 109 (1267) BIII
-7 -6 -5 -4 -3 -2 -1 0-3-2-101
Diff
eren
ce (%
)Elevation (degrees)
10
12
14
16
18
20
App
aren
t tem
pera
ture
(o C)
Measurment
Simulation (+0.265 W/m2/ster)
σerr = 1.42%
-7 -6 -5 -4 -3 -2 -1 0
2.32
2.34
2.36
2.38
2.4
2.42
2.44
Rad
ianc
e (W
/m2 /s
ter)
ATAL 107 (1255) BII
-7 -6 -5 -4 -3 -2 -1 0-1
-0.5
0
0.5
Diff
eren
ce (%
)
Elevation (degrees)
14.5
15
15.5
16
16.5
17
App
aren
t tem
pera
ture
(o C)
Measurment
Simulation (-0.113 W/m2/ster)
σerr = 0.19%
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Results
• Glint
Relative azimuth (degrees)E
leva
tion
(deg
rees
)
ATAL 145 (1416) BII reference image
-4 -2 0 2 4 6
-7
-6
-5
-4
-3
-2
-1
0
Rad
ianc
e (W
/m2 /s
ter)
0
0.5
1
1.5
2
2.5
3
3.5
4A
B
B
A
-7 -6 -5 -4 -3 -2 -1 00
0.5
1
1.5
2ATAL 145 (1416) BII vertical
Rad
ianc
e (W
/m2
/ste
r)
-7 -6 -5 -4 -3 -2 -1 0-100
0
100
200
Elevation (degrees)
Diff
eren
ce (%
)
Measurment
Simulation (-0.05 W/m 2 /ster)
-4 -3 -2 -1 0 1 2 3 4 5 60
0.5
1
1.5ATAL 145 (1416) BII horizontal
Rad
ianc
e (W
/m2
/ste
r)
-4 -3 -2 -1 0 1 2 3 4 5 6
-20
0
20
Relative Azimuth (degrees)
Diff
eren
ce (%
)
Measurment
Simulation (-0.05 W/m 2/ster)
(Note: Cirrus cloud modeled using Aeronet AOD data)
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Results
• Glint
Relative Azimuth (degrees)E
leva
tion
(deg
rees
)
ATAL 64 (902) BII reference image
-6 -4 -2 0 2
-8
-7
-6
-5
-4
-3
-2
-1
Rad
ianc
e (W
/m2 /s
ter)
5
10
15
20AA
B
B
-9 -8 -7 -6 -5 -4 -3 -2 -1 01
2
3
4
5
6
7ATAL 64 (902) BII vertical
Elevation (degrees)
Rad
ianc
e (W
/m2 /s
ter)
MeasurementSimulation (+0.2 W/m2/ster)Horizon correction
-8 -6 -4 -2 0 2 40
1
2
3
4
5
6ATAL 64 (902) BII horizontal
Relative Azimuth (degrees)
Rad
ianc
e (W
/m2 /s
ter)
MeasurementSimulation (+0.2 W/m2/ster)Horizon correction
Ross, V., Dion, D., "Sea surface slope statistics derived from Sun glint radiance measurements and their apparent dependence on sensor elevation, J. Geophys. Res., 112, C09015, (2007)
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Conclusions
• A radiatively coupled sea surface BRDF is important in maritime environment radiative transfer
• MODTRAN 5 v3 will introduce a coupled sea surface BRDF
• Analysis of MIRAMER radiometric images supports the validation of the MODTRAN sea radiance implementation– Simulations and measurements agree well within experimental
uncertainties
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