Standoff determination of the particle size and concentration of small optical depth clouds based on double-scattering measurements: validation with calibrated target plates and limitations for daytime and nighttime measurements
Nathalie Roy and Gilles Roy, "Standoff determination of the particle size and concentration of small optical depth clouds based on double-scattering measurements: validation with calibrated target plates and limitations for daytime and nighttime measurements," Appl. Opt. 47, 4235-4252 (2008)
Diffractive target plates are used to emulate aerosols of known size and concentration. These target plates are used to validate and determine the sensitivity of a multiple-field-of-view lidar signal inversion technique based on double-scattering measurement to retrieve the particle size and the concentration of small optical depth clouds. We estimate that nighttime and daytime quantification (size and concentration) is possible for optical depths as low as 0.005 and 0.016, respectively. The recovery technique limiting factors are the shot noise, the laser features, the optical lens quality, the background illumination level, the background aerosol fluctuations, and the noise introduced by the lidar detector, a gated intensified camera (camera G-ICCD).
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Diameters, Densities , and Total Number N of Etched Particles on Fused Silica Plates
Diameter ()
()
N (particles)
5
50,800
20
3175
50
508
Table 2
Size Retrieval and Its Associated Error, Target at , Gate Width a
Etched-Particle Size, Position
Test
Nighttime
Daytime
,
Cloudy, ,
Mid-cloud, ,
Mid-cloud, ,
S.R.
Error
S.R.
Error
S.R.
Error
S.R.
Error
,
1
21.9
9%
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
2
21.9
10%
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
3
23.4
17%
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
,
1
46.6
47.0
47.9
45.0
2
48.5
48.9
46.4
45.7
3
47.0
48.1
44.5
45.5
,
1
20.1
1%
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
2
19.8
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
3
19.7
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
,
1
47.2
46.2
N.a.
N.a.
48.9
2
47.3
52.2
4%
N.a.
N.a.
46.8
3
46.8
44.1
N.a.
N.a.
42.2
The target plate is located from the lidar system for a camera gate width of . S.R., size retrieval; w.s., wind speed; b.l., background light level in photons/gate opening included in (half-angle). N.a., not available because the data are too noisy; thus it is impossible to distinguish the diffraction peak.
Table 3
Size Retrieval and Its Associated Error, Target at , Gate Width a
Etched Particle Size, Position
Test
Nighttime
Daytime
,
Cloudy, ,
Mid-cloud, ,
Mid-cloud, ,
S.R.
Error
S.R.
Error
S.R.
Error
S.R.
Error
,
1
21.2
6%
22.3
12%
22.5
12%
N.a.
N.a.
2
23.1
16%
17.9
21.2
6%
N.a.
N.a.
3
19.9
18.6
18.4
N.a.
N.a.
,
1
47.2
53.2
7%
48.0
52.3
5%
2
46.8
45.8
49.1
38.5
3
49.5
46.8
46.1
46.1
,
1
19.0
N.a.
N.a.
N.a.
N.a.
21.5
7%
2
18.9
N.a.
N.a.
N.a.
N.a.
23.2
16%
3
19.4
N.a.
N.a.
N.a.
N.a.
19.1
,
1
48.9
54.6
9%
49.9
46.6
2
47.5
54.4
9%
54.9
10%
47.2
3
49.0
55.4
11%
56.1
12%
48.6
The target plate is located from the lidar system for a camera gate width of . S.R., size retrieval; w.s., wind speed; b.l.: background light level in photons/gate opening included in (half-angle). N.a.: not available because the data are too noisy; thus it is impossible to distinguish the diffraction peak.
Table 4
Optical Depth Retrieval and Its Associated Error, Target at , Gate Width a
Etched-Particle Size, Position
Nighttime
Daytime
,
Cloudy, ,
Mid-cloud, ,
Mid-cloud, ,
O.D.
Error
O.D.
Error
O.D.
Error
O.D.
Error
155.5
,
1%
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
,
6%
175.5
,
21%
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
,
8%
3%
28%
Mean value for each background condition
3%
5%
10%
Mean value for all trials
0.0412
The target plate is located from the lidar system for a camera gate width of . w.s., wind speed; b.l., background light level in photons/gate opening included in (half-angle). N.a., not available because the data are too noisy; thus it is impossible to distinguish the diffraction peak.
Table 5
Optical Depth Retrieval and Its Associated Error, Target at , Gate Width a
Etched-Particle Size, Position
Nighttime
Daytime
,
Cloudy, ,
Mid-cloud, ,
Mid-cloud, ,
O.D.
Error
O.D.
Error
O.D.
Error
O.D.
Error
155.5
,
21%
28%
25%
N.a.
,
175.5
,
21%
N.a.
N.a.
54%
,
13%
0%
3%
Mean value for each background condition
8%
5%
0.042017%
5%
12%
Mean value for all trials
0.0430
The target plate is located from the lidar system for a camera gate width of . w.s., wind speed; b.l., background light level in photons/gate opening included in (half-angle). N.a., not available because the data are too noisy; thus it is impossible to distinguish the diffraction peak.
Table 6
Comparison of Mean Readout and Dark Current Noise Values in Each Ring with 1 and 100 Laser Pulses Accumulated on the CCD Chip
Ring FOVs Delimitation (mrad)
No. of Pixels
1 Laser Pulse Accumulated (counts)
100 Laser Pulses Accumulated (counts)
Mean Readout Noise per Laser Pulse
Dark Current Noise per Laser Pulse
Mean Readout Noise per Laser Pulse
Dark Current Noise per Laser Pulse
0.17–0.20
14
7.48
0.07
0.20–0.23
22
9.38
0.09
0.23–0.27
32
11.31
0.11
0.27–0.31
44
13.27
0.13
0.31–0.36
56
14.97
0.15
0.36–0.42
88
18.76
0.19
0.42–0.49
114
21.35
0.21
0.49–0.58
138
23.49
0.23
0.58–0.67
212
29.12
0.29
0.67–0.78
272
32.98
0.33
0.78–0.91
384
39.19
0.39
0.91–1.06
508
45.08
0.45
1.06–1.23
688
52.46
0.52
1.23–1.44
936
61.19
0.61
1.44–1.68
1264
71.11
0.71
1.68–1.95
1736
83.33
0.83
1.95–2.27
2336
96.66
0.97
2.27–2.65
3168
112.57
1.13
2.65–3.09
4308
131.27
1.31
3.09–3.60
5840
152.84
1.53
3.60–4.19
7960
178.44
1.78
4.19–4.88
10752
207.38
2.07
Tables (6)
Table 1
Diameters, Densities , and Total Number N of Etched Particles on Fused Silica Plates
Diameter ()
()
N (particles)
5
50,800
20
3175
50
508
Table 2
Size Retrieval and Its Associated Error, Target at , Gate Width a
Etched-Particle Size, Position
Test
Nighttime
Daytime
,
Cloudy, ,
Mid-cloud, ,
Mid-cloud, ,
S.R.
Error
S.R.
Error
S.R.
Error
S.R.
Error
,
1
21.9
9%
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
2
21.9
10%
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
3
23.4
17%
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
,
1
46.6
47.0
47.9
45.0
2
48.5
48.9
46.4
45.7
3
47.0
48.1
44.5
45.5
,
1
20.1
1%
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
2
19.8
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
3
19.7
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
,
1
47.2
46.2
N.a.
N.a.
48.9
2
47.3
52.2
4%
N.a.
N.a.
46.8
3
46.8
44.1
N.a.
N.a.
42.2
The target plate is located from the lidar system for a camera gate width of . S.R., size retrieval; w.s., wind speed; b.l., background light level in photons/gate opening included in (half-angle). N.a., not available because the data are too noisy; thus it is impossible to distinguish the diffraction peak.
Table 3
Size Retrieval and Its Associated Error, Target at , Gate Width a
Etched Particle Size, Position
Test
Nighttime
Daytime
,
Cloudy, ,
Mid-cloud, ,
Mid-cloud, ,
S.R.
Error
S.R.
Error
S.R.
Error
S.R.
Error
,
1
21.2
6%
22.3
12%
22.5
12%
N.a.
N.a.
2
23.1
16%
17.9
21.2
6%
N.a.
N.a.
3
19.9
18.6
18.4
N.a.
N.a.
,
1
47.2
53.2
7%
48.0
52.3
5%
2
46.8
45.8
49.1
38.5
3
49.5
46.8
46.1
46.1
,
1
19.0
N.a.
N.a.
N.a.
N.a.
21.5
7%
2
18.9
N.a.
N.a.
N.a.
N.a.
23.2
16%
3
19.4
N.a.
N.a.
N.a.
N.a.
19.1
,
1
48.9
54.6
9%
49.9
46.6
2
47.5
54.4
9%
54.9
10%
47.2
3
49.0
55.4
11%
56.1
12%
48.6
The target plate is located from the lidar system for a camera gate width of . S.R., size retrieval; w.s., wind speed; b.l.: background light level in photons/gate opening included in (half-angle). N.a.: not available because the data are too noisy; thus it is impossible to distinguish the diffraction peak.
Table 4
Optical Depth Retrieval and Its Associated Error, Target at , Gate Width a
Etched-Particle Size, Position
Nighttime
Daytime
,
Cloudy, ,
Mid-cloud, ,
Mid-cloud, ,
O.D.
Error
O.D.
Error
O.D.
Error
O.D.
Error
155.5
,
1%
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
,
6%
175.5
,
21%
N.a.
N.a.
N.a.
N.a.
N.a.
N.a.
,
8%
3%
28%
Mean value for each background condition
3%
5%
10%
Mean value for all trials
0.0412
The target plate is located from the lidar system for a camera gate width of . w.s., wind speed; b.l., background light level in photons/gate opening included in (half-angle). N.a., not available because the data are too noisy; thus it is impossible to distinguish the diffraction peak.
Table 5
Optical Depth Retrieval and Its Associated Error, Target at , Gate Width a
Etched-Particle Size, Position
Nighttime
Daytime
,
Cloudy, ,
Mid-cloud, ,
Mid-cloud, ,
O.D.
Error
O.D.
Error
O.D.
Error
O.D.
Error
155.5
,
21%
28%
25%
N.a.
,
175.5
,
21%
N.a.
N.a.
54%
,
13%
0%
3%
Mean value for each background condition
8%
5%
0.042017%
5%
12%
Mean value for all trials
0.0430
The target plate is located from the lidar system for a camera gate width of . w.s., wind speed; b.l., background light level in photons/gate opening included in (half-angle). N.a., not available because the data are too noisy; thus it is impossible to distinguish the diffraction peak.
Table 6
Comparison of Mean Readout and Dark Current Noise Values in Each Ring with 1 and 100 Laser Pulses Accumulated on the CCD Chip