Markus Pahlow,1
Detlef Müller,2
Matthias Tesche,2
Heike Eichler,2
Graham Feingold,3
Wynn L. Eberhard,3
and Ya-Fang Cheng4
1When this research was performed M. Pahlow (markus.pahlow@rub.de) was with the NOAA Earth System Research Laboratory, 325 Broadway, Boulder, Colorado 80305; he is now with the Ruhr-University Bochum, Universitässtrasse 150, 44801 Bochum, Germany.
2D. Müller, M. Tesche, and H. Eichler are with the Leibniz Institute for Tropospheric Research, Permoserstrasse 15, 04318 Leipzig, Germany.
3G. Feingold and W. L. Eberhard are with the NOAA Earth System Research Laboratory, 325 Broadway, Boulder, Colorado 80305.
4Y.-F. Cheng is with the College of Environmental Sciences, Peking University, Beijing 100871, China.
Markus Pahlow, Detlef Müller, Matthias Tesche, Heike Eichler, Graham Feingold, Wynn L. Eberhard, and Ya-Fang Cheng, "Retrieval of aerosol properties from combined multiwavelength lidar and sunphotometer measurements," Appl. Opt. 45, 7429-7442 (2006)
Simulation studies were carried out with regard to the feasibility of using combined
observations from sunphotometer (SPM) and lidar for microphysical characterization of
aerosol particles, i.e., the retrieval of effective radius, volume, and surface-area
concentrations. It was shown that for single, homogeneous aerosol layers, the
aerosol parameters can be retrieved with an average accuracy of
for a wide
range of particle size distributions. Based on the simulations, an instrument
combination consisting of a lidar that measures particle backscattering at 355 and
, and a SPM that measures at three to four channels in the range from
340 to
is a promising tool for aerosol characterization. The inversion algorithm
has been tested for a set of experimental data. The comparison with the particle size
distribution parameters, measured with in situ instrumentation at the lidar site,
showed good agreement.
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Combinations of Lidar and SPM Wavelengths and Their Respective Number of Extinction (α) and Backscatter (β) Channels
Combination
Wavelengths
Extinction and Backscatter
I
SPM (i)–(iv) and lidar at 355 and 1574 nm (both elastic backscatter)
3α + 2β, 4α + 2β, 5α + 2β, 6α + 2β
SPM wavelengths for (i)–(iv) are (i) 340, 500, and 1020 nm (ii) 340, 500, 870, and 1020 nm (iii) 340, 500, 670, 870, and 1020 nm (iv) 340, 440, 500, 670, 870, and 1020 nm
II
SPM (i)–(iv)
3α, 4α, 5α, 6α
III
SPM (i)–(iv) and lidar at 355 nm (Raman) and 1574 nm (elastic backscatter)
3α + 2β, 4α + 2β, 5α + 2β, 6α + 2β
IV
SPM (i)–(iv) and lidar at 355, 532, and 1064 nm (all elastic backscatter)
3α + 3β, 4α + 3β, 5α + 3β, 6α + 3β
V
SPM (i)–(iv) and lidar at 355, 532, and 1574 nm (all elastic backscatter)
3α + 3β, 4α + 3β, 5α + 3β, 6α + 3β
VI
SPM (i)–(iv) and lidar at 355 nm (elastic backscatter)
3α + 1β, 4α + 1β, 5α + 1β, 6α + 1β
Table 2
Wavelengths Used by Lidar Monitoring Networks to Determine Backscatter and Extinction Coefficientsa
λ (nm) Network
Backscatter Coefficients
Extinction Coefficients
355
523
532
1064
355
532
EARLINET
X
X
X
X
X
AD-NET
X
X
X
X
X
NIES lidar network
X
X
REALM
X
X
X
X
X
MPLNET
X
EARLINET, AD-NET, National Institute for Environmental Studies (NIES) lidar network, regional east atmospheric lidar mesonet (REALM), MPLNET. Note that the number of instruments with specific measurement capabilities may vary within each network.
Table 3
sd and Retrieval Parameters Used as Input for the Simulationsa
Aerosol Parameter
sd 1: Urban-Industrial and Mixed (GSFC Greenbelt, Maryland),b Fine Mode Only
sd 4: Same as sd 3, but Different m to Account for Sea Salte
sd 5: Same as sd 1 but with Different m
sd 6: Same as sd 1 but with Different m
sd 7: Same as sd 1 but with Different m
rg [μm]
0.09
0.03
0.3
0.3
0.09
0.09
0.09
σ
1.46
2.25
1.46
1.46
1.46
1.46
1.46
cn
1
1
1
1
1
1
1
reff [μm]
0.13
0.16
0.43
0.43
0.13
0.13
0.13
m
1.40 − i0.003
1.40 − i0.003
1.40 − i0.003
1.49 − i0.0001
1.60 − i0.01
1.50 − i0.03
1.40 − i0.01
rmin [μm]
0.05:0.05:0.25
0.01:0.05:0.25
0.05:0.05:0.35
0.05:0.05:0.35
0.05:0.05:0.25
0.05:0.05:0.25
0.05:0.05:0.25
rmax [μm]
0.8:0.2:2.0
0.8:0.2:2.0
0.8:0.2:2.0
0.8:0.2:2.0
0.8:0.2:2.0
0.8:0.2:2.0
0.8:0.2:2.0
The median diameter is denoted as rg, σ is the geometric standard deviation, cn is the total number concentration (can be selected arbitrarily), reff is the effective radius, m is the complex index of refraction, and rmin and rmax are the minimum and maximum particle radii specified for the retrieved sd's.
Reference 30.
According to Ref. 32.
According to Ref. 33.
Index of refraction from Ref. 34.
Table 4
Maximum Error in
reff,csa, and cv for Combinations I, VI, and II and sd 1–7
reff
csa
cv
I
VI
II
I
VI
II
I
VI
II
sd 1
11
18
16
21
19
28
30
30
37
sd 2
14
35
22
44
55
120
9
17
24
sd 3
2
9
13
14
10
25
14
12
8
sd 4
5
17
22
2
13
18
5
21
40
sd 5
12
9
12
60
56
60
40
40
40
sd 6
17
24
7
25
25
10
18
29
9
sd 7
14
11
16
17
10
27
25
20
33
Table 5
Overall Comparison of Wavelength Combinations I, VI, and II for the Maximum Retrieval Error in reff,csa, and cv for sd 1–7a
I–VI
I–II
VI–II
−
10
14
14
=
3
3
1
+
8
4
6
The comparison shows how often the maximum error was smaller (−), equal (=), and larger (+) for I compared with VI, I compared with II, and VI compared with II.
Table 6
Wavelengths of Extinction (α) and Backscatter (β) Coefficients Used for the Two Test Cases of Inversion with Experimental Data
Test Case
α [nm]
β [nm]
1
380, 440, 670, 780, and 1020
—
2
380, 440, 532, 780, 870, and 1020
381 and 532
Table 7
Results from Inversion with SPM Data, Combined Lidar, SPM Data, In Situ Measurements for Effective Radius reff, Surface-Area Concentration csa, and Volume Concentration cv
Aerosol Parameter
Inversion
In Situ
SPM
Lidar and SPM
reff [μm]
0.24 ± 0.01
0.22 ± 0.01
0.22 ± 0.01
csa [μm2 cm−3]
7.8 × 105 ± 1.4 × 105
9.3 × 105 ± 1.1 × 105
8.8 × 105 ± 0.9 × 105
cv [μm3 cm−3]
8.0 × 104 ± 1.2 × 104
5.9 × 104 ± 0.6 × 104
7.0 × 104 ± 0.7 × 104
Tables (7)
Table 1
Combinations of Lidar and SPM Wavelengths and Their Respective Number of Extinction (α) and Backscatter (β) Channels
Combination
Wavelengths
Extinction and Backscatter
I
SPM (i)–(iv) and lidar at 355 and 1574 nm (both elastic backscatter)
3α + 2β, 4α + 2β, 5α + 2β, 6α + 2β
SPM wavelengths for (i)–(iv) are (i) 340, 500, and 1020 nm (ii) 340, 500, 870, and 1020 nm (iii) 340, 500, 670, 870, and 1020 nm (iv) 340, 440, 500, 670, 870, and 1020 nm
II
SPM (i)–(iv)
3α, 4α, 5α, 6α
III
SPM (i)–(iv) and lidar at 355 nm (Raman) and 1574 nm (elastic backscatter)
3α + 2β, 4α + 2β, 5α + 2β, 6α + 2β
IV
SPM (i)–(iv) and lidar at 355, 532, and 1064 nm (all elastic backscatter)
3α + 3β, 4α + 3β, 5α + 3β, 6α + 3β
V
SPM (i)–(iv) and lidar at 355, 532, and 1574 nm (all elastic backscatter)
3α + 3β, 4α + 3β, 5α + 3β, 6α + 3β
VI
SPM (i)–(iv) and lidar at 355 nm (elastic backscatter)
3α + 1β, 4α + 1β, 5α + 1β, 6α + 1β
Table 2
Wavelengths Used by Lidar Monitoring Networks to Determine Backscatter and Extinction Coefficientsa
λ (nm) Network
Backscatter Coefficients
Extinction Coefficients
355
523
532
1064
355
532
EARLINET
X
X
X
X
X
AD-NET
X
X
X
X
X
NIES lidar network
X
X
REALM
X
X
X
X
X
MPLNET
X
EARLINET, AD-NET, National Institute for Environmental Studies (NIES) lidar network, regional east atmospheric lidar mesonet (REALM), MPLNET. Note that the number of instruments with specific measurement capabilities may vary within each network.
Table 3
sd and Retrieval Parameters Used as Input for the Simulationsa
Aerosol Parameter
sd 1: Urban-Industrial and Mixed (GSFC Greenbelt, Maryland),b Fine Mode Only
sd 4: Same as sd 3, but Different m to Account for Sea Salte
sd 5: Same as sd 1 but with Different m
sd 6: Same as sd 1 but with Different m
sd 7: Same as sd 1 but with Different m
rg [μm]
0.09
0.03
0.3
0.3
0.09
0.09
0.09
σ
1.46
2.25
1.46
1.46
1.46
1.46
1.46
cn
1
1
1
1
1
1
1
reff [μm]
0.13
0.16
0.43
0.43
0.13
0.13
0.13
m
1.40 − i0.003
1.40 − i0.003
1.40 − i0.003
1.49 − i0.0001
1.60 − i0.01
1.50 − i0.03
1.40 − i0.01
rmin [μm]
0.05:0.05:0.25
0.01:0.05:0.25
0.05:0.05:0.35
0.05:0.05:0.35
0.05:0.05:0.25
0.05:0.05:0.25
0.05:0.05:0.25
rmax [μm]
0.8:0.2:2.0
0.8:0.2:2.0
0.8:0.2:2.0
0.8:0.2:2.0
0.8:0.2:2.0
0.8:0.2:2.0
0.8:0.2:2.0
The median diameter is denoted as rg, σ is the geometric standard deviation, cn is the total number concentration (can be selected arbitrarily), reff is the effective radius, m is the complex index of refraction, and rmin and rmax are the minimum and maximum particle radii specified for the retrieved sd's.
Reference 30.
According to Ref. 32.
According to Ref. 33.
Index of refraction from Ref. 34.
Table 4
Maximum Error in
reff,csa, and cv for Combinations I, VI, and II and sd 1–7
reff
csa
cv
I
VI
II
I
VI
II
I
VI
II
sd 1
11
18
16
21
19
28
30
30
37
sd 2
14
35
22
44
55
120
9
17
24
sd 3
2
9
13
14
10
25
14
12
8
sd 4
5
17
22
2
13
18
5
21
40
sd 5
12
9
12
60
56
60
40
40
40
sd 6
17
24
7
25
25
10
18
29
9
sd 7
14
11
16
17
10
27
25
20
33
Table 5
Overall Comparison of Wavelength Combinations I, VI, and II for the Maximum Retrieval Error in reff,csa, and cv for sd 1–7a
I–VI
I–II
VI–II
−
10
14
14
=
3
3
1
+
8
4
6
The comparison shows how often the maximum error was smaller (−), equal (=), and larger (+) for I compared with VI, I compared with II, and VI compared with II.
Table 6
Wavelengths of Extinction (α) and Backscatter (β) Coefficients Used for the Two Test Cases of Inversion with Experimental Data
Test Case
α [nm]
β [nm]
1
380, 440, 670, 780, and 1020
—
2
380, 440, 532, 780, 870, and 1020
381 and 532
Table 7
Results from Inversion with SPM Data, Combined Lidar, SPM Data, In Situ Measurements for Effective Radius reff, Surface-Area Concentration csa, and Volume Concentration cv