Nadège Martiny,1
Robert Frouin,2
and Richard Santer1
1N. Martiny (martiny@mren2.univ-littoral.fr) and R. Santer are with the Laboratoire Inter-disciplinaire des Sciences de l’Environnement, Etudes des Systèmes Littoraux et Côtiers, Unité Mixte de Recherche 8013, Université du Littoral Côte d’Opale, 32 Avenue Foch, 62930 Wimereux, France
2R. Frouin is with the Climate Research Division, Scripps Institution of Oceanography, University of California San Diego, 8810 La Jolla Shores Drive, La Jolla, California 92037
The radiometric calibration of the Sea-Viewing Wide-Field-of-View Sensor (SeaWiFS) in the near infrared (band 8, centered on 865 nm) is evaluated by use of ground-based radiometer measurements of solar extinction and sky radiance in the Sun’s principal plane at two sites, one located 13 km off Venice, Italy, and the other on the west coast of Lanai Island, Hawaii. The aerosol optical thickness determined from solar extinction is used in an iterative scheme to retrieve the pseudo aerosol phase function, i.e., the product of single-scattering albedo and phase function, in which sky radiance is corrected for multiple scattering effects. No assumption about the aerosol model is required. The aerosol parameters are the inputs into a radiation-transfer code used to compute the SeaWiFS radiance. The calibration method has a theoretical inaccuracy of plus or minus 2.0–3.6%, depending on the solar zenith angle and the SeaWiFS geometry. The major source of error is in the calibration of the ground-based radiometer operated in radiance mode, assumed to be accurate to ±2%. The establishment of strict criteria for atmospheric stability, angular geometry, and surface conditions resulted in selection of only 26 days for the analysis during 1999–2000 (Venice site) and 1998–2001 (Lanai site). For these days the measured level-1B radiance from the SeaWiFS Project Office was generally lower than the corresponding simulated radiance in band 8 by 7.0% on average, ±2.8%.
Robert E. Eplee, Wayne D. Robinson, Sean W. Bailey, Dennis K. Clark, P. Jeremy Werdell, Menghua Wang, Robert A. Barnes, and Charles R. McClain Appl. Opt. 40(36) 6701-6718 (2001)
Robert E. Eplee, Gerhard Meister, Frederick S. Patt, Robert A. Barnes, Sean W. Bailey, Bryan A. Franz, and Charles R. McClain Appl. Opt. 51(36) 8702-8730 (2012)
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Average values of mid-latitude summer and mid-latitude winter profiles: associated relative errors for six couples of solar and view zenith angles (θs, θυ).
Table 4
Influence of Aerosol Polarization on TOA Radiance Simulationsa
ν
θυ(°)
τa(865 nm) = 0.05
τa(865 nm) = 0.15
θs = 20°
θs = 60°
θs = 20°
θs = 60°
m1
m2
m3
m1
m2
m3
m1
m2
m3
m1
m2
m3
−4.5
20°
−1.10
−0.97
−0.91
−0.93
−0.81
−0.73
−2.04
−1.80
−1.60
−1.06
−0.86
−0.75
60°
−0.77
−0.68
−0.66
+1.21
+1.04
+0.89
−1.17
−0.93
−0.80
+1.70
+1.30
+1.05
−4.0
20°
−0.63
−0.51
−0.48
−0.59
−0.51
−0.44
−1.08
−0.81
−0.89
−0.90
−0.62
−0.50
60°
−0.52
−0.47
−0.45
+0.83
+0.65
+0.50
−0.78
−0.68
−0.60
+1.15
+0.90
+0.63
−3.5
20°
−0.30
−0.21
−0.19
−0.32
−0.25
−0.19
−0.50
−0.30
−0.47
−0.53
−0.39
−0.24
60°
−0.25
−0.23
−0.27
+0.29
+0.17
+0.03
−0.51
−0.41
−0.42
+0.49
+0.20
+0.06
The relative difference between nonpolarized and polarized radiance is indicated in percent. Three Junge power law slopes (ν = −4.5, −4.0, −3.5), two view zenith angles (θν = 20°, 60°), two values of aerosol optical thickness (νa = 0.05, 0.15), two solar zenith angles (θs = 20°, 60°), and three aerosol refractive indices (m1 = 1.33, m2 = 1.45, and m3 = 1.55–0.005i) are considered. Azimuth angle difference Δφ is set to 90°.
Table 5
Characteristics of SeaWiFS Images Selected for the Near-Infrared Calibrationa
Day
GMT
θs (°)
θυ (°)
Δφ (°)
Θ (°)
χ (°)
τa (865 nm)
PPL
V990803
10:46
28.1
60.6
58.9
130.2
49.8
0.074
1
V990906
11:12
38.9
39.7
56.2
145.3
34.7
0.101
2
V990908
12:41
45.3
67.4
63.3
124.4
55.6
0.032
1
V990912
12:21
44.9
57.1
62.0
131.6
48.4
0.051
2
V991126
11:50
67.4
25.4
30.4
133.6
46.4
0.050
3
V991222
12:53
72.8
69.1
75.8
109.0
71.0
0.021
2
V991231
12:55
72.3
69.8
76.8
108.0
72.0
0.019
2
V000425
12:13
35.7
53.1
56.4
138.3
41.7
0.130
2
V000609
12:06
26.2
47.6
47.1
145.8
34.2
0.126
5
V000618
12:04
25.4
46.0
47.0
146.9
33.1
0.063
1
V000623
12:25
27.6
60.5
50.3
133.9
46.1
0.091
4
V000727
12:27
31.1
61.7
56.6
131.0
49.0
0.120
3
V000731
12:04
29.7
45.8
54.0
144.6
35.4
0.021
3
V000807
12:13
52.8
32.3
57.5
137.7
42.3
0.023
4
V000810
12:45
36.5
69.4
58.9
124.8
55.2
0.038
2
V000908
12:24
44.0
59.4
62.5
130.0
50.0
0.018
2
V000910
12:13
43.8
51.8
60.3
135.7
44.3
0.026
6
V000911
12:56
48.4
73.0
63.7
120.8
59.2
0.043
2
V000912
12:01
43.7
42.1
55.2
143.3
36.7
0.062
5
L980712
23:10
8.4
50.3
21.4
137.5
42.5
0.036
1
L981026
23:07
36.1
47.7
53.5
143.4
36.6
0.020
1
L990127
23:08
39.8
48.7
68.2
133.4
46.6
0.047
3
L990427
22:25
6.9
39.5
50.8
144.5
35.5
0.062
3
L990616
23:15
10.9
56.7
22.8
133.20
46.8
0.044
1
L991129
22:26
42.4
37.1
52.7
146.6
33.4
0.044
5
L010301
22:58
28.5
38.0
58.2
147.9
32.1
0.056
2
The Day column indicates the site (V, Venice; L, Lanai) and the date (year, month, day). The GMT column indicates the time of the SeaWiFS overpass. The geometry of the corresponding SeaWiFS image is defined with solar zenith angle θs; view zenith angle θυ, azimuth difference Δφ, and scattering angles Θ and χ. Aerosol optical thickness τa(865 nm) is measured by CIMEL at the time of SeaWiFS overpass. The PPL column indicates the number of proper PPL protocols during the morning.
Table 6
Values of Five Pseudo Phase Functions at the Θ and χ Scattering Angles on 9 June 2000 over the Venice Sitea
Ground Observation Time
ωaPa(Θ)
ΔωaPa(Θ)
ωaPa(χ)
ΔωaPa(χ)
5:37
0.266
0.004
2.561
0.019
7:12
0.241
0.021
2.561
0.019
8:13
0.258
0.004
2.604
0.062
9:18
0.249
0.013
2.685
0.143
12:18
0.256
0.006
2.461
0.081
Average
0.254
0.005
2.574
0.007
Θ = 145.8° and χ = 34.2°.
Table 7
Summary of the Aerosol Single-Scattering Albedos ωa Derived at Hours hi for Each Selected Day
Average values of mid-latitude summer and mid-latitude winter profiles: associated relative errors for six couples of solar and view zenith angles (θs, θυ).
Table 4
Influence of Aerosol Polarization on TOA Radiance Simulationsa
ν
θυ(°)
τa(865 nm) = 0.05
τa(865 nm) = 0.15
θs = 20°
θs = 60°
θs = 20°
θs = 60°
m1
m2
m3
m1
m2
m3
m1
m2
m3
m1
m2
m3
−4.5
20°
−1.10
−0.97
−0.91
−0.93
−0.81
−0.73
−2.04
−1.80
−1.60
−1.06
−0.86
−0.75
60°
−0.77
−0.68
−0.66
+1.21
+1.04
+0.89
−1.17
−0.93
−0.80
+1.70
+1.30
+1.05
−4.0
20°
−0.63
−0.51
−0.48
−0.59
−0.51
−0.44
−1.08
−0.81
−0.89
−0.90
−0.62
−0.50
60°
−0.52
−0.47
−0.45
+0.83
+0.65
+0.50
−0.78
−0.68
−0.60
+1.15
+0.90
+0.63
−3.5
20°
−0.30
−0.21
−0.19
−0.32
−0.25
−0.19
−0.50
−0.30
−0.47
−0.53
−0.39
−0.24
60°
−0.25
−0.23
−0.27
+0.29
+0.17
+0.03
−0.51
−0.41
−0.42
+0.49
+0.20
+0.06
The relative difference between nonpolarized and polarized radiance is indicated in percent. Three Junge power law slopes (ν = −4.5, −4.0, −3.5), two view zenith angles (θν = 20°, 60°), two values of aerosol optical thickness (νa = 0.05, 0.15), two solar zenith angles (θs = 20°, 60°), and three aerosol refractive indices (m1 = 1.33, m2 = 1.45, and m3 = 1.55–0.005i) are considered. Azimuth angle difference Δφ is set to 90°.
Table 5
Characteristics of SeaWiFS Images Selected for the Near-Infrared Calibrationa
Day
GMT
θs (°)
θυ (°)
Δφ (°)
Θ (°)
χ (°)
τa (865 nm)
PPL
V990803
10:46
28.1
60.6
58.9
130.2
49.8
0.074
1
V990906
11:12
38.9
39.7
56.2
145.3
34.7
0.101
2
V990908
12:41
45.3
67.4
63.3
124.4
55.6
0.032
1
V990912
12:21
44.9
57.1
62.0
131.6
48.4
0.051
2
V991126
11:50
67.4
25.4
30.4
133.6
46.4
0.050
3
V991222
12:53
72.8
69.1
75.8
109.0
71.0
0.021
2
V991231
12:55
72.3
69.8
76.8
108.0
72.0
0.019
2
V000425
12:13
35.7
53.1
56.4
138.3
41.7
0.130
2
V000609
12:06
26.2
47.6
47.1
145.8
34.2
0.126
5
V000618
12:04
25.4
46.0
47.0
146.9
33.1
0.063
1
V000623
12:25
27.6
60.5
50.3
133.9
46.1
0.091
4
V000727
12:27
31.1
61.7
56.6
131.0
49.0
0.120
3
V000731
12:04
29.7
45.8
54.0
144.6
35.4
0.021
3
V000807
12:13
52.8
32.3
57.5
137.7
42.3
0.023
4
V000810
12:45
36.5
69.4
58.9
124.8
55.2
0.038
2
V000908
12:24
44.0
59.4
62.5
130.0
50.0
0.018
2
V000910
12:13
43.8
51.8
60.3
135.7
44.3
0.026
6
V000911
12:56
48.4
73.0
63.7
120.8
59.2
0.043
2
V000912
12:01
43.7
42.1
55.2
143.3
36.7
0.062
5
L980712
23:10
8.4
50.3
21.4
137.5
42.5
0.036
1
L981026
23:07
36.1
47.7
53.5
143.4
36.6
0.020
1
L990127
23:08
39.8
48.7
68.2
133.4
46.6
0.047
3
L990427
22:25
6.9
39.5
50.8
144.5
35.5
0.062
3
L990616
23:15
10.9
56.7
22.8
133.20
46.8
0.044
1
L991129
22:26
42.4
37.1
52.7
146.6
33.4
0.044
5
L010301
22:58
28.5
38.0
58.2
147.9
32.1
0.056
2
The Day column indicates the site (V, Venice; L, Lanai) and the date (year, month, day). The GMT column indicates the time of the SeaWiFS overpass. The geometry of the corresponding SeaWiFS image is defined with solar zenith angle θs; view zenith angle θυ, azimuth difference Δφ, and scattering angles Θ and χ. Aerosol optical thickness τa(865 nm) is measured by CIMEL at the time of SeaWiFS overpass. The PPL column indicates the number of proper PPL protocols during the morning.
Table 6
Values of Five Pseudo Phase Functions at the Θ and χ Scattering Angles on 9 June 2000 over the Venice Sitea
Ground Observation Time
ωaPa(Θ)
ΔωaPa(Θ)
ωaPa(χ)
ΔωaPa(χ)
5:37
0.266
0.004
2.561
0.019
7:12
0.241
0.021
2.561
0.019
8:13
0.258
0.004
2.604
0.062
9:18
0.249
0.013
2.685
0.143
12:18
0.256
0.006
2.461
0.081
Average
0.254
0.005
2.574
0.007
Θ = 145.8° and χ = 34.2°.
Table 7
Summary of the Aerosol Single-Scattering Albedos ωa Derived at Hours hi for Each Selected Day
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