The aerosol database from OPAC

(Optical Properties of Aerosols and Clouds)

FIRST PART : OPAC dataset of microphysical and optical propperties of aerosols and clouds online access

The following optical properties of aerosols and clouds have been archived (see, e.g. Van de Hulst, 1981, BAMS98 for explicit formulas and definitions):

  1. extinction coefficient (km-1)
  2. scattering coefficient (km-1)
  3. absorption coefficient (km-1)
  4. single scattering albedo
  5. asymmetry parameter
  6. volume phase function (km-1 sr-1)

Parameters 1 to 4 are archived for 61 wavelengths in case of aerosols and water clouds and for 32 wavelengths in case of ice clouds. Parameter 5 is archived for the same wavelengths and for 167 values of angles.

AEROSOL DATA

Table 1. Microphysical and optical(*) properties of aerosol components in dry state (from Table 1c of BAMS98). Here σ, rmodN, rmodV, rmin, and rmax, are parameters of the lognormal size distributions (see section 3c of BAMS98).
The term ρ is the density of the aerosol particles and
M* is the aerosol mass per cubic meter air, integrated over the size distribution and normalized to 1 particle per cubic centimeter of air. The term M* [(milligram m-3) ] (particles cm-3)-1] is calculated with a cutoff radius of 7.5 micrometer.

Component Online access to data files(**) σ rmodN

micrometers

rmodV

micrometers

rmin

micrometers

rmax

micrometers

ρ

g cm-3

M*

(milligram m-3)/(part. cm-3)

Insoluble INSO 2.51 0.471 6.00 0.005 20.0 2.0 23.7
Water-soluble WASO(+) 2.24 0.0212 0.15 0.005 20.0 1.8 1.34 10-3
Soot SOOT 2.00 0.0118 0.05 0.005 20.0 1.0 5.99 10-5
Sea salt (acc.mode) SSAM(+) 2.03 0.209 0.94 0.005 20.0 2.2 0.802
Sea salt (coa. mode) SSCM(+) 2.03 1.75 7.90 0.005 60.0 2.2 224
Mineral (nuc. mode) MINM 1.95 0.07 0.27 0.005 20.0 2.6 0.0278
Mineral (acc. mode) MIAM 2.00 0.39 1.60 0.005 20.0 2.6 5.53
Mineral (coa. mode) MICM 2.15 1.90 11.00 0.005 60.0 2.6 324
Mineral-transported MITR 2.20 0.50 3.00 0.02 5.0 2.5 15.9
Sulfate droplets SUSO(+) 2.03 0.0695 0.31 0.005 20.0 1.7 0.0228

(*) Optical properties of aerosol components as well as their complex refractive indices are stored in the data files listed in column 2.

(**) Click with the mouse left button on a file of interest to view its content. To download a file, click it with the mouse right button and select the “Save as” item of the pop-un menu.

(+) Aerosol components which are able to take up water: the data are available for eight values of relative humidity: 0%, 50%, 70%, 80%, 90%, 95%, 98%, 99%.

WATER CLOUDS AND FOG

Table 2. Microphysical and optical(*) properties of the water-cloud and fog models (from Table 1a of BAMS98) at 61 wavelengths between 0.25 and 40 micrometers. Values listed in columns 3 to 9 are parameters of the cloud size distribution function (for explanation see section 3a of BAMS98). The liquid water content L is listed in column 10.

Component Online access to data files(**) rmod

(micrometers)

α γ a B reff

(micrometers)

N

(cm-3)

L

(g m-3)

Stratus (continental) STCO 4.7 5 1.05 9.792 10-3 0.938 7.33 250 0.28
Stratus (maritime) STMA 6.75 3 1.30 3.818 10-3 0.193 11.30 80 0.30
Cumulus (cont., clean) CUCC 4.8 5 2.16 1.105 10-3 0.0782 5.77 400 0.26
Cumulus (cont., polluted) CUCP 3.53 8 2.15 8.118 10-4 0.247 4.00 1300 0.30
Cumulus (maritime) CUMA 10.4 4 2.34 5.674 10-5 0.00713 12.68 65 0.44
Fog FOGR 8.06 4 1.77 3.041 10-4 0.0562 10.70 15 0.058

(*) Optical properties of water cloud and fog models are stored in the data files listed in column 2 of the table.

(**) Click with the mouse left button on a file of interest to view its content. To download a file, click it with the mouse right button and select the “Save as” item of the pop-un menu.

ICE CLOUDS (CIRRUS)

Table 5. Microphysical and optical(*) properties of ice cloud model (from Table 1b of BAMS98) at 32 wavelengths between 0.28 and 10 micrometers. Values listed in columns 3 to 10 are parametrs of the ice cloud size distribution function (for explanation see section 3b of the paper by BAMS98). The ice content I is listed in column 10.

Component Online access to data files(**) a1 b1 a2 b2 x0 f reff

(micrometers)

N

(cm-3)

I

(g m-3)

Cirrus 1: -25° C CIR1 4.486 108 -2.417 1.545 x 1014 -4.376 670 0.909 91.7 0.107 0.0260
Cirrus 2: -50° C CIR2 5.352 x 1010 -3.545 3.48 57.4 0.0225 0.00193
Cirrus 3:

-50° C

+ small particles(***)

CIR3 5.352 x 1010 -3.545 3.48 34.3 0.578 0.00208

(*) Optical properties of ice cloud models are stored in the data files listed in column 2 of the table.

(**) Click with the mouse left button on a file of interest to view its content. To download a file, click it with the mouse right button and select the “Save as” item of the pop-un menu.

(***) Cirrus 3 is the same distribution as cirrus 2 between 20 and 2000 micrometers. Additionally, there are 0.169 particles m-3 between 2 and 6 micrometers and 0.387 particles m-3 between 6 and 20 micrometers.

SECOND PART : OPAC FORTRAN PROGRAM

The OPAC FORTRAN program allows the user to extract data from the dataset and to calculate additional optical properties of mixtures of the stored clouds and aerosol components.

The following optical properties can be computed (see paragraph 4 of Hess et al., 1998 for explications and formulas):

  • the extinction coefficient (km-1),
  • the scattering coefficient (km-1),
  • the absorption coefficient (km-1),
  • the volume phase function (km-1 sr-1),
  • the single scattering albedo,
  • the asymmetry parameter,
  • the aerosol optical depth
  • spectral turbidity factor
  • lidar ratio
  • mass extinction cross section
  • mass absorption cross section
  • normalized extinction coefficient
  • spectrally weighted coefficients
  • Angström coefficients
  •  visibility
  • refractive index

MIXING OF ATMOSPHERIC PARTICLES

OPAC allows handling of mixtures of the given components, freely defined by the user. Moreover, default values of 10 aerosol types are proposed to span the range of climatologically important aerosols. The detailed description of the standard aerosol types is given in paper Hess et al., 1998 and in Koepke et al., 1997.

The principal properties of 10 aerosol models are listed in Table 6: aerosol types in column 1, aerosol components in column 2, number densities Ni of aerosol components in particles cm-3 in column 3, aerosol optical depth at wavelength of 0.55 micrometers in column 4.Column 5 provides online access to files with selected optical properties of standard aerosols, listed in column 1, at wavelength of 0.55 micrometers, for the relative humidity of 80%, calculated by the OPAC FORTAN.

Table 3. Composition and optical depth of 10 aerosol types (compiled from Tables 3,4 Hess et al., 1998).

Aerosol types Components Ni

(cm-3)

Optical depth

(at 0.55 micrometers)

Online access(*) to data files with selected optical properties at 0.55 micrometers and at relative humidity of 80%
Continental clean total

water soluble

insoluble

2600

2600

0.15

0.064 COCL
Continental averaged total

water soluble

insoluble

soot

15300

7000

0.4

8300

0.151 COAV
Continental polluted total

water soluble

insoluble

soot

50000

15700

0.6

34300

0.327 COPO
Urban total

water soluble

insoluble

soot

158000

28000

1.5

130000

0.643 URBA
Desert total

water soluble

mineral (nuc.)

mineral (acc.)

mineral (coa.)

2300

2000

269.5

30.5

0.142

0.286 DESE
Maritime clean total

water soluble

see salt (acc.)

see salt (coa.)

1520

1500

20

3.2 10-3

0.096 MACL
Maritime polluted total

water soluble

see salt (acc.)

see salt (coa.)

soot

9000

3800

20

3.2 10-3

5180

0.117 MAPO
Maritime tropical total

water soluble

see salt (acc.)

see salt (coa.)soot

600

590

10

1.3 10-3

0.056 MATR
Arctic total

water soluble

insoluble

see salt (acc.)

soot

6600

1300

0.01

1.9

5300

0.063 ARCT
Antarctic total

sulfate

sea salt (acc.)

mineral (tra.)

43

42.9

0.047

0.0053

0.072 ANTA
  • 61 wavelengths (in micrometers) for aerosols
    and water clouds
    0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.9 1.0
    1.25 1.5 1.75 2.0 2.5 3.0 3.2 3.39 3.5 3.75 4.0 4.5 5.0 5.5 6.0 6.2 6.5
    7.2 7.9 8.2 8.5 8.7 9.0 9.2 9.5 9.8 10.0 10.6 11.0 11.5 12.5 13.0 14.0
    14.8 15.0 16.4 17.2 18.0 18.5 20.0 21.3 22.5 25.0 27.9 30.0 35.0 40.0
  • 32 wavelengths (in micrometers) for ice clouds
    (cirrus)
    0.280 0.300 0.320 0.350 0.355 0.400 0.423 0.532 0.535 0.550 0.635
    0.780 0.830 0.873 1.015 1.064 1.100 1.200 1.400 1.449 1.504 1.555 1.615
    1.850 1.905 2.000 2.190 2.600 3.077 3.413 3.700 10.00
  • 167 scattering angles (in degree) used for computations of phase functions:0.000 0.001 0.002 0.003 0.004 0.005 0.010 0.015 0.020 0.025 0.030
    0.040 0.060 0.080 0.100 0.120 0.140 0.160 0.180 0.200 0.220 0.240 0.260
    0.280 0.300 0.350 0.400 0.450 0.500 0.550 0.600 0.650 0.700 0.750 0.800
    0.850 0.900 0.950 1.000 1.050 1.100 1.150 1.200 1.250 1.300 1.350 1.400
    1.450 1.500 1.550 1.600 1.650 1.700 1.750 1.800 1.850 1.900 1.950 2.000
    2.500 3.000 3.500 4.000 4.500 5.000 6.000 7.000 8.000 9.000 10.000 11.000
    12.000 13.000 14.000 15.000 16.000 17.000 18.000 19.000 20.000 21.000 22.000
    23.000 24.000 25.000 26.000 27.000 28.000 29.000 30.000 32.000 34.000 36.000
    38.000 40.000 42.000 44.000 46.000 48.000 50.000 52.000 54.000 56.000 58.000
    60.000 62.000 64.000 66.000 68.000 70.000 72.000 74.000 76.000 78.000 80.000
    82.000 84.000 86.000 88.000 90.000 92.000 94.000 96.000 98.000 100.000
    102.000 104.000 106.000 108.000 110.000 112.000 114.000 116.000 118.000
    120.000 122.000 124.000 126.000 128.000 130.000 132.000 134.000 136.000
    138.000 140.000 142.000 144.000 146.000 148.000 150.000 152.000 154.000
    156.000 158.000 160.000 162.000 164.000 166.000 168.000 170.000 172.000
    174.000 176.000 178.000 179.000 179.500 180.000