Validation of fascod3 and modtran3: comparison of model calculations with ground-based and airborne interferometer observations under clear-sky conditions
Jinxue Wang, Gail P. Anderson, Henry E. Revercomb, and Robert O. Knuteson
Jinxue Wang,1,3
Gail P. Anderson,1
Henry E. Revercomb,2
and Robert O. Knuteson2
1When this research was performed, J. Wang and G. P. Anderson were with the U.S. Air Force Phillips Laboratory, Geophysics Directorate, 29 Randolph Road, Hanscom Air Force Base, Massachusetts 01731-3010.
2Space Science and Engineering Center, University of Wisconsin-Madison, 1225 W. Dayton Street, Madison, Wisconsin 53706.
3J. Wang is now with the Atmospheric Chemistry Division, National Center for Atmospheric Research, P.O. Box 3000, Boulder, Colorado 80307-3000.
Jinxue Wang, Gail P. Anderson, Henry E. Revercomb, and Robert O. Knuteson, "Validation of fascod3 and modtran3: comparison of model calculations with ground-based and airborne interferometer observations under clear-sky conditions," Appl. Opt. 35, 6028-6040 (1996)
The validation of fascod3 and modtran3 against ground-based and airborne high-resolution Michelson interferometer measurements under clear-sky conditions is presented. Important considerations including water vapor continuum, frequency-dependent sea surface emissivity in the IR window region, and spectral resolution of modtran3 in the comparison of model calculations with high-resolution interferometer measurements are discussed. Our results indicate that it is not adequate to assume sea surface emissivity of 1.0 [ɛ(ν) = 1.0] or a constant in the simulation of upwelling radiance observed by the airborne Michelson interferometer. The use of spectral emissivity (frequency-dependent emissivity) leads to much better agreement between model calculations and interferometer measurements in the IR window region from 750.0 to 1050.0 cm−1. This could have important implications for the retrieval of sea surface temperature, thin cirrus properties, and aerosol parameters because of the sea surface emissivity of 1.0 assumption commonly used by many researchers. Comparisons of modtran3 calculations with interferometer measurements show that the agreement might not be adequate at the nominal resolution of 2.0 cm−1, and further spectral degradation might be necessary to improve the agreement between measurements and modtran3 calculations. modtran should be used with caution for relatively high spectral resolution remote-sensing applications.
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Characteristics of the AERI and Spectra Used in the fascod3 Comparison
Channel 1
520–1800 cm−1
Channel 2
1800–3020 cm−1
Optical path
1.03702766 cm
Data spacing
0.48214722 cm−1
HWHM
0.290906 cm−1
Interferometer
Bomem MB 100
Table 2
Atmospheric Temperature and Profiles of Radiatively Important Trace Species at 45 Levels from 0.0 to 30.0 km
Z (km)
P(mbar)
T (°C)
H2O (g/kg)
CO2 (ppmv) (×102)
O3 (ppmv)
N2O (ppmv) (×10−1)
CO (ppmv) (×10−1)
CH4 (ppmv)
0.000
999.30
−0.34
1.157
3.606
1.526
3.072
1.592
1.822
0.060
991.78
−0.57
1.352
3.603
1.927
3.072
1.585
1.817
0.187
976.08
−0.71
1.764
3.598
2.163
3.072
1.570
1.806
0.365
954.56
−1.92
1.753
3.591
2.347
3.072
1.550
1.790
0.585
928.39
−3.00
1.910
3.582
2.432
3.071
1.524
1.771
0.843
898.44
−3.93
1.911
3.572
2.436
3.071
1.494
1.748
1.138
865.48
−3.92
1.992
3.560
2.763
3.071
1.460
1.723
1.466
830.07
−5.61
1.995
3.550
2.881
3.070
1.430
1.700
1.825
792.63
−7.89
1.857
3.550
2.947
3.070
1.430
1.700
2.214
753.69
−10.35
1.294
3.550
3.048
3.069
1.430
1.700
2.633
713.58
−12.89
1.243
3.550
3.399
3.069
1.430
1.700
3.079
672.94
−13.26
9.662
3.550
3.654
3.068
1.430
1.700
3.552
632.19
−15.23
7.741
3.550
4.322
3.068
1.430
1.700
4.051
591.88
−13.43
1.094
3.550
3.846
3.067
1.430
1.700
4.575
552.33
−14.98
1.145
3.550
4.579
3.067
1.430
1.700
5.124
513.33
−18.21
6.432
3.550
4.533
3.066
1.430
1.700
5.697
475.20
−21.36
3.946
3.550
4.066
3.065
1.430
1.700
6.293
437.93
−25.50
3.125
3.550
4.669
3.064
1.430
1.700
6.912
401.66
−30.99
2.370
3.550
4.195
3.064
1.430
1.700
7.554
366.54
−36.00
1.294
3.550
4.441
3.063
1.430
1.700
8.218
332.69
−41.89
1.206
3.550
4.562
3.062
1.430
1.700
8.904
300.25
−47.37
1.096
3.550
4.775
3.061
1.430
1.700
9.611
269.47
−51.56
4.450
3.550
6.478
3.060
1.430
1.700
10.338
240.77
−53.91
1.027
3.550
1.038
3.060
1.430
1.700
11.087
214.18
−54.05
6.910
3.550
1.545
3.060
1.430
1.700
11.856
189.96
−54.52
4.290
3.550
1.920
3.060
1.430
1.700
12.644
167.94
−55.40
3.380
3.550
2.266
3.060
1.430
1.700
13.453
147.96
−57.50
3.070
3.550
2.713
3.060
1.430
1.700
14.281
129.89
−61.20
2.960
3.550
1.559
3.060
1.430
1.700
15.128
113.80
−61.70
2.920
3.550
3.678
3.060
1.430
1.700
15.994
99.39
−62.80
2.860
3.550
5.364
3.060
1.430
1.700
16.879
86.48
−66.70
2.810
3.550
6.806
3.060
1.430
1.700
17.783
75.15
−65.20
2.810
3.550
1.177
3.060
1.430
1.700
18.704
65.18
−61.00
2.800
3.550
2.027
3.060
1.430
1.700
19.644
56.34
−58.57
2.790
3.550
2.510
3.060
1.430
1.700
20.602
48.46
−62.27
2.790
3.550
2.823
3.060
1.430
1.700
21.577
41.68
−58.51
2.800
3.550
3.642
3.060
1.430
1.700
22.570
35.72
−56.70
2.830
3.550
4.202
3.060
1.430
1.700
23.581
30.51
−57.24
2.840
3.550
4.394
3.060
1.430
1.700
24.609
25.99
−57.44
2.880
3.550
4.983
3.060
1.430
1.700
25.653
22.09
−56.92
2.890
3.550
5.335
3.060
1.430
1.700
26.715
18.74
−53.46
2.910
3.550
5.913
3.060
1.430
1.700
27.793
15.83
−55.70
2.930
3.550
5.842
3.060
1.430
1.700
28.888
13.36
−51.60
2.930
3.550
7.839
3.060
1.430
1.700
30.000
11.23
−54.09
2.960
3.550
8.349
3.060
1.430
1.700
Table 3
Spectral Resolution and Maximum Optical Path Difference of the HIS for the Eastern Pacific Flight on 14 April 1986
HIS Band
Spectral Range (cm−1)
Spectral Resolution (cm−1)
Maximum Optical Path (cm)
I
600–1080
0.3640322
1.3735050
II
1080–1850
0.6370564
0.7848598
III
2000–2600
0.6370564
0.7848598
Table 4
Condition and Profiles of Temperature, Water vapor, and Ozone of the HIS Eastern Pacific Experimenta,b
Index
Altitude (km)
Pressure (mbar)
Sonde Temp. (K)
H2O Relative Humidity, (%)
CO2 (ppmv)
Retrieved O3 (g/kg) (×10−3)
1
0.0000
1000.0
286.9
62.9
349.0
0.045
2
0.4310
950.0
285.2
44.4
349.0
0.045
3
0.6990
920.0
284.6
26.5
349.0
0.046
4
1.3570
850.0
282.2
15.7
349.0
0.047
5
2.0630
780.0
278.6
11.9
349.0
0.048
6
2.9390
700.0
273.4
27.2
349.0
0.050
7
3.2880
670.0
271.0
30.7
349.0
0.050
8
3.9000
620.0
267.0
39.0
349.0
0.050
9
4.5530
570.0
263.0
47.1
349.0
0.052
10
5.5500
500.0
256.1
36.9
349.0
0.057
11
5.9330
475.0
253.6
61.1
349.0
0.059
12
6.6650
430.0
248.4
44.5
349.0
0.066
13
7.1870
400.0
244.7
21.4
349.0
0.070
14
8.1310
350.0
237.9
17.9
349.0
0.085
15
9.1870
300.0
229.7
2.8
349.0
0.120
16
10.3880
250.0
220.2
2.5
349.0
0.173
17
11.7930
200.0
211.5
11.9
349.0
0.270
18
13.5900
150.0
213.7
4.8
349.0
0.500
19
14.2480
135.0
213.3
4.9
349.0
0.600
20
15.2450
115.0
211.1
10.1
349.0
0.850
21
16.1090
100.0
211.3
3.5
349.0
1.150
22
17.1180
85.0
212.8
1.2
349.0
1.650
23
18.3270
70.0
212.4
1.2
349.0
2.400
24
19.2870
60.0
212.6
1.0
349.0
3.200
25
20.4230
50.0
213.1
0.6
349.0
4.200
Supplied by R. Knuteson.
Date, 14 April 1986; Time, 1800 UTC; Location, off the California coast (−120.5, +34.7); SST, 287.3 K (HIS estimate with 1.0 sea surface emissivity assumption); Surface altitude, unknown; Surface air temperature, unknown; Surface wind speed, unknown; Comment, area and time average of conventional NWS sondes. Retrieved ozone.
Table 5
Emissivity of Sea Water at Zero Zenith Angle and Zero Surface Wind Speed in the IR Window Regiona
Characteristics of the AERI and Spectra Used in the fascod3 Comparison
Channel 1
520–1800 cm−1
Channel 2
1800–3020 cm−1
Optical path
1.03702766 cm
Data spacing
0.48214722 cm−1
HWHM
0.290906 cm−1
Interferometer
Bomem MB 100
Table 2
Atmospheric Temperature and Profiles of Radiatively Important Trace Species at 45 Levels from 0.0 to 30.0 km
Z (km)
P(mbar)
T (°C)
H2O (g/kg)
CO2 (ppmv) (×102)
O3 (ppmv)
N2O (ppmv) (×10−1)
CO (ppmv) (×10−1)
CH4 (ppmv)
0.000
999.30
−0.34
1.157
3.606
1.526
3.072
1.592
1.822
0.060
991.78
−0.57
1.352
3.603
1.927
3.072
1.585
1.817
0.187
976.08
−0.71
1.764
3.598
2.163
3.072
1.570
1.806
0.365
954.56
−1.92
1.753
3.591
2.347
3.072
1.550
1.790
0.585
928.39
−3.00
1.910
3.582
2.432
3.071
1.524
1.771
0.843
898.44
−3.93
1.911
3.572
2.436
3.071
1.494
1.748
1.138
865.48
−3.92
1.992
3.560
2.763
3.071
1.460
1.723
1.466
830.07
−5.61
1.995
3.550
2.881
3.070
1.430
1.700
1.825
792.63
−7.89
1.857
3.550
2.947
3.070
1.430
1.700
2.214
753.69
−10.35
1.294
3.550
3.048
3.069
1.430
1.700
2.633
713.58
−12.89
1.243
3.550
3.399
3.069
1.430
1.700
3.079
672.94
−13.26
9.662
3.550
3.654
3.068
1.430
1.700
3.552
632.19
−15.23
7.741
3.550
4.322
3.068
1.430
1.700
4.051
591.88
−13.43
1.094
3.550
3.846
3.067
1.430
1.700
4.575
552.33
−14.98
1.145
3.550
4.579
3.067
1.430
1.700
5.124
513.33
−18.21
6.432
3.550
4.533
3.066
1.430
1.700
5.697
475.20
−21.36
3.946
3.550
4.066
3.065
1.430
1.700
6.293
437.93
−25.50
3.125
3.550
4.669
3.064
1.430
1.700
6.912
401.66
−30.99
2.370
3.550
4.195
3.064
1.430
1.700
7.554
366.54
−36.00
1.294
3.550
4.441
3.063
1.430
1.700
8.218
332.69
−41.89
1.206
3.550
4.562
3.062
1.430
1.700
8.904
300.25
−47.37
1.096
3.550
4.775
3.061
1.430
1.700
9.611
269.47
−51.56
4.450
3.550
6.478
3.060
1.430
1.700
10.338
240.77
−53.91
1.027
3.550
1.038
3.060
1.430
1.700
11.087
214.18
−54.05
6.910
3.550
1.545
3.060
1.430
1.700
11.856
189.96
−54.52
4.290
3.550
1.920
3.060
1.430
1.700
12.644
167.94
−55.40
3.380
3.550
2.266
3.060
1.430
1.700
13.453
147.96
−57.50
3.070
3.550
2.713
3.060
1.430
1.700
14.281
129.89
−61.20
2.960
3.550
1.559
3.060
1.430
1.700
15.128
113.80
−61.70
2.920
3.550
3.678
3.060
1.430
1.700
15.994
99.39
−62.80
2.860
3.550
5.364
3.060
1.430
1.700
16.879
86.48
−66.70
2.810
3.550
6.806
3.060
1.430
1.700
17.783
75.15
−65.20
2.810
3.550
1.177
3.060
1.430
1.700
18.704
65.18
−61.00
2.800
3.550
2.027
3.060
1.430
1.700
19.644
56.34
−58.57
2.790
3.550
2.510
3.060
1.430
1.700
20.602
48.46
−62.27
2.790
3.550
2.823
3.060
1.430
1.700
21.577
41.68
−58.51
2.800
3.550
3.642
3.060
1.430
1.700
22.570
35.72
−56.70
2.830
3.550
4.202
3.060
1.430
1.700
23.581
30.51
−57.24
2.840
3.550
4.394
3.060
1.430
1.700
24.609
25.99
−57.44
2.880
3.550
4.983
3.060
1.430
1.700
25.653
22.09
−56.92
2.890
3.550
5.335
3.060
1.430
1.700
26.715
18.74
−53.46
2.910
3.550
5.913
3.060
1.430
1.700
27.793
15.83
−55.70
2.930
3.550
5.842
3.060
1.430
1.700
28.888
13.36
−51.60
2.930
3.550
7.839
3.060
1.430
1.700
30.000
11.23
−54.09
2.960
3.550
8.349
3.060
1.430
1.700
Table 3
Spectral Resolution and Maximum Optical Path Difference of the HIS for the Eastern Pacific Flight on 14 April 1986
HIS Band
Spectral Range (cm−1)
Spectral Resolution (cm−1)
Maximum Optical Path (cm)
I
600–1080
0.3640322
1.3735050
II
1080–1850
0.6370564
0.7848598
III
2000–2600
0.6370564
0.7848598
Table 4
Condition and Profiles of Temperature, Water vapor, and Ozone of the HIS Eastern Pacific Experimenta,b
Index
Altitude (km)
Pressure (mbar)
Sonde Temp. (K)
H2O Relative Humidity, (%)
CO2 (ppmv)
Retrieved O3 (g/kg) (×10−3)
1
0.0000
1000.0
286.9
62.9
349.0
0.045
2
0.4310
950.0
285.2
44.4
349.0
0.045
3
0.6990
920.0
284.6
26.5
349.0
0.046
4
1.3570
850.0
282.2
15.7
349.0
0.047
5
2.0630
780.0
278.6
11.9
349.0
0.048
6
2.9390
700.0
273.4
27.2
349.0
0.050
7
3.2880
670.0
271.0
30.7
349.0
0.050
8
3.9000
620.0
267.0
39.0
349.0
0.050
9
4.5530
570.0
263.0
47.1
349.0
0.052
10
5.5500
500.0
256.1
36.9
349.0
0.057
11
5.9330
475.0
253.6
61.1
349.0
0.059
12
6.6650
430.0
248.4
44.5
349.0
0.066
13
7.1870
400.0
244.7
21.4
349.0
0.070
14
8.1310
350.0
237.9
17.9
349.0
0.085
15
9.1870
300.0
229.7
2.8
349.0
0.120
16
10.3880
250.0
220.2
2.5
349.0
0.173
17
11.7930
200.0
211.5
11.9
349.0
0.270
18
13.5900
150.0
213.7
4.8
349.0
0.500
19
14.2480
135.0
213.3
4.9
349.0
0.600
20
15.2450
115.0
211.1
10.1
349.0
0.850
21
16.1090
100.0
211.3
3.5
349.0
1.150
22
17.1180
85.0
212.8
1.2
349.0
1.650
23
18.3270
70.0
212.4
1.2
349.0
2.400
24
19.2870
60.0
212.6
1.0
349.0
3.200
25
20.4230
50.0
213.1
0.6
349.0
4.200
Supplied by R. Knuteson.
Date, 14 April 1986; Time, 1800 UTC; Location, off the California coast (−120.5, +34.7); SST, 287.3 K (HIS estimate with 1.0 sea surface emissivity assumption); Surface altitude, unknown; Surface air temperature, unknown; Surface wind speed, unknown; Comment, area and time average of conventional NWS sondes. Retrieved ozone.
Table 5
Emissivity of Sea Water at Zero Zenith Angle and Zero Surface Wind Speed in the IR Window Regiona