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The software package OPAC has been developed
by Hess and Koepke (Meteorolgisches Institut der Universitaet Muenchen,
Germany) and Schult (Max-Plank-Institut fuer Meteorologie, Hamburg, Germany).
A complete description of OPAC is given in M. Hess, P. Koepke, and I. Schult,
Bulletin
of the American Meteorological Society, 79, 831-844, 1998, refered
to as BAMS98 in the following, for details of this presentation.
This page provides description of the following
OPAC-related subjects:
OPAC consists of two parts:
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Deepak and Gerber, 1983; Shettl
and Fenn, 1979;
d'Almedia et al., 1991; Koepke et al., 1997 |
(*) Two sea-salt modes are given to allow for a different
wind-speed-dependent increase of particle number for particles of different
size (Koepke et al., 1997).
(**) Three mineral modes are given to allow to consider
increasing of relative amount of large particles for increasing turbidity
(BAMS98).
Table 2a. Water clouds used in the OPAC software package (BAMS98)
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Stratus (continental) (water clouds) | Tampieri and Tomasi 1976; Diem, 1948; Hofmann and Roth, 1989. |
Stratus (maritime) (water clouds) | Tampieri and Tomasi 1976; Stephens et al., 1978. |
Cumulus (continental, clean) (water clouds) | Tampieri and Tomasi 1976; Squires 1958; Leatich et al., 1992. |
Cumulus (continental, polluted) (water clouds) | Tampieri and Tomasi 1976; Diem, 1948; Fitzgerald and Spyers-Duran, 1973. |
Cumulus (maritime) (water clouds) | Tampieri and Tomasi 1976. |
Fog | Tampieri and Tomasi 1976. |
Table 2b. Ice clouds used in the OPAC software package (BAMS98)
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Cirrus 1 (T=-25° C) (ice clouds) | Heymsfield and Platt, 1984; Strauss et al., 1997; Hess and Wiegner, 1994. | |
Cirrus 2 (T=-50° C) (ice clouds) | ||
Cirrus 3 (T=-50° C)+ small particles (ice clouds) |
OPAC DATASET OF MICROPHYSICAL AND OPTICAL PROPERTIES 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The following optical properties of aerosols and clouds have been archived (see, e.g. Van de Hulst, 1981, BAMS98 for explicit formulas and definitions):
Table 3. Microphysical and
optical(*) properties of aerosol components in dry state (from
Table 1c of BAMS98). Here ,
rmodN,
rmodV,
rmin,
and rmax, are parameters
of the lognormal size distributions (see section 3c of BAMS98).
The term
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.
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micrometers |
micrometers |
micrometers |
micrometers |
g cm-3 |
(milligram m-3)/(part. cm-3) |
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(*) 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%.
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(micrometers) |
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(micrometers) |
(cm-3) |
(g m-3) |
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(*) 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.
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(micrometers) |
(cm-3) |
(g m-3) |
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5.352 x 1010 |
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-50° C + small particles(***) |
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(*) 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.
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. Click here
with the mouth right button and select "Save link as" item of the pop-up
menu to download the gzipped tar version of the OPAC software package.
The following optical properties can be computed
(see paragraph 4 of paper Hess
et al., 1998 for explications and formulas):
MIXING OF ATMOSPHERIC PARTICLES
The capability of OPAC to mix optical properties
of components (see paragraph 3) is most interesting
with respect to aerosol because aerosol usually is a combination of particles
of different origin. Nevertheless, it is also possible to define external
mixtures of clouds and aerosols, thus modeling the effect of interstitial
aerosol particles in clouds. 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 calculated using Eq.
2 with height profiles from paper
Hess
et al., 1998 in column 4, and 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 6. Composition and optical depth of 10 aerosol types (compiled from Tables 3,4 from paper Hess et al., 1998)
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(cm-3) |
(at 0.55 micrometers) |
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Continental clean | total
water soluble insoluble |
2600 0.15 |
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Continental averaged | total
water soluble insoluble soot |
7000 0.4 8300 |
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Continental polluted | total
water soluble insoluble soot |
15700 0.6 34300 |
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COPO |
Urban | total
water soluble insoluble soot |
28000 1.5 130000 |
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Desert | total
water soluble mineral (nuc.) mineral (acc.) mineral (coa.) |
2000 269.5 30.5 0.142 |
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Maritime clean | total
water soluble see salt (acc.) see salt (coa.) |
1500 20 3.2 10-3 |
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Maritime polluted | total
water soluble see salt (acc.) see salt (coa.) soot |
3800 20 3.2 10-3 5180 |
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Maritime tropical | total
water soluble see salt (acc.) see salt (coa.)soot |
590 10 1.3 10-3 |
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Arctic | total
water soluble insoluble see salt (acc.) soot |
1300 0.01 1.9 5300 |
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Antarctic | total
sulfate sea salt (acc.) mineral (tra.) |
42.9 0.047 0.0053 |
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(*)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.
The facilities of the access to the OPAC software as well as the installation instructions are given on the OPAC web site (a copy of this page is available on the GEISA web site). Click here with the mouth right button and select "Save link as" item of the pop-up menu to download the gzipped tar version of the OPAC. |
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