Several parameters are very important if you want a realistic model.. However if you consider the single parameter, then it is the Spectral AOD

You can also use our database or the mathematica and fortran models I have developed.

look at:

C. Levoni, M. Cervino, R. Guzzi, F. Torricella: Atmospheric aerosol optical properties

: a Data base of radiative characteristics for dierent component and classes, 1997

Applied Optics, vol 36 pp 8031-8041

All it is fully described. If you are interested I can supply fortran and mathematica software and a tutorial

Howdy,

Water vapour is an important parameter as well, but it is not present in the original version of OPAC. I made an OPAC version in FORTRAN 77, where the effect of water vapour on the optical properties of aerosols is included. It gives rather big differences at high water vapour concentrations for AOD at 550 nm and horizontal visibility, and must hence be taken into account. With water vapour present in the model, smog formation can be simulated.

Cheers,

Frank

OPAC lets you specify aerosol types (upto 4 variety), their number concentrations, vertical distribution and relative humidity. Importance of parameter will depend on what is your end objective but in most circumstances, I have found aerosol types and their number concentrations most important inputs.

OPAC can calculate the several optical properties of aerosols: extinction coefficient, scattering coefficient, absorption coefficient, single-scattering albedo (SSA), asymmetry parameter and aerosol optical depth (AOD).

The scattering cross coefficient (or extinction coefficient) is related to the probability of light being scattered by an aerosol. Analogously, the absorption coefficient is related to the probability of absorption. The sum of these coefficients (absorption and scattering) results in the extinction coefficient

The single-scattering albedo is the key parameter to understand the influence of different aerosol types on the radiative balance (Hansen et al., 1997). The SSA of a single particle is defined as SSA=Qscat/(Qscat+Qabs), where Qscat and Qabs are the scattering and absorption efficiencies of the aerosol, calculated by the Mie theory.

The interpretation of the SSA is that for SSA=1 the aerosol is totally scattering. As a consequence the aerosol will tend to lower the global mean surface temperature. This is the case of sea salt and sulfate aerosol. On the other hand, strongly absorbent aerosols, such as BC, can have a value as low as 0.2. The value of SSA is important as there is a threshold SSA (King et al. 1999). Below that threshold, aerosol will increase the global mean surface temperature.

Another output is the asymmetry parameter (g). Since the radiation scattered by aerosols is asymmetrical, the phase function describes the angular distribution of radiation scattered by a particle or by particles comprising an aerosol composite. In practice, the phase function is parameterized with only the parameter g, which is the mean cosine of the scattering angle, found by integration over the complete scattering phase function. The interpretations of the asymmetry factor is that for g=1 the aerosol completely scatters in the forward direction, whereas g=0 denotes symmetric scattering. For spherical particles, g is related to particle size in a systematic way: the larger the particle size, the more the scattering in the forward hemisphere.

Finally, the aerosol optical depth (AOD) is considered to be the simplest and most representative parameter for characterizing the aerosols present in the atmosphere. The AOD calculation, based on the Bouguer-Lambert-Beer law, is the result of integrating the aerosol extinction coefficient (in km-1) over the entire atmosphere, which is the sum of several possible layers. For this, the distribution of aerosol particles with height for each layer is described by means of exponential profiles.

Refs:

Hansen, J., M. Sato, and R. Ruedy: Radiative forcing and climate response, 1997: J. Geophys. Res., 102, 6831–6864.

King, M. D., Y. J. Kaufman, D. Tanré, and T. Nakajima, 1999: T. Remote sensing of tropospheric aerosols from space: Past, present, and future. Bull. Amer. Meteorol. Soc., 80, 2229–2259.

You may also want to check whether the hard-coded lognormal aerosol size distributions of OPAC are appropriate for your application, since the modeled quantities are extremely dependent on aerosol radius.

Howdy,

Maybe an important disadvantage of OPAC is that it assumes aerosols to be globular, which is certainly not the case for most of the aerosols, except when they are soaked with a water droplet. Hence, the radius of a realistic aerosol particle, is very variable, not even an ellipsoid comes close to the number of radii for real aerosol particles. Still some work to do to more rigorously describe the shape of aerosol particles in OPAC. Just image that one needs about seven radii to describe an aerosol particle. When one wants to calculate the volume or weight of the particle, one ends up with some tricky sevenfold integrals to be solved in polar coordinates. Anyone wanting to give a go? Or Numerical solutions maybe, leading to approximations again!

Besides that, OPAC, gives a fair idea of aerosol properties and behaviour even, when it is assumed that they are globular.

Cheers,

Frank

Thank you Frank Veroustraete sir for kind suggetions

sir I am using original version of OPAC , sir I am very new in this field. ca i use your OPAC  FORTRAN code and can compare the result of  both.

Thank you sir

Regards

Raj

No problem Raj,

Just send me your email address.

Frank

Thank you sir so kind of you 

Sir my Email is [email protected]

Regards

Raj

Frank

I like to comment on your comment on the shape of atmospheric aerosol particles that are most important in light extinction. These are composed of a large fraction of slat-like components. And these are highly hygroscopic. This means that at most humidity conditions in the atmosphere they have attracted (indeed) a large amount of water and are deliquesced and thus have a rounded shape.

This is evidenced when one looks at collected particles in an electron microscope: the submicron aerosol particles are mostly circular-shaped with signs of evaporation. This latter is obvious from the extended work of prof van Grieken.

You might be interested in the AEROgui online tool. See

http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-13-00162.1?ai=sg&ui=19t9&af=H

Hi Harry and Chris,

Harry, it seems that the globular assumption for the shape of atmospheric aerosols is not so bad after all, seen the effect of water vapour, especially on hydrophobic aerosols. Could one conclude from this, that water vapour may be one of the most important variables in an adpated version of the OPAC model, e.g. a version including the effect of water vapour on the optical properties of the aerosol types in the model?

Chris, thanks for your interesting AEROgui. A nice tool indeed to determine the optical properties of aerosols. Again an important factor in slecting tyhe right aerosol mix and scenraio's under different meteorological conditions. Seen the complexity of aerosol modellling as well as its remote sensing, these tools are prime in the development of better RS exctractions chemes of aerosol loads and properties.

Thanks both of you for the interesting aspects of aerosol remote sensing and optical properties modelling you have raised.

Cheers,

Frank

Frank

A note at the bottom of the first  table: http://ether.ipsl.jussieu.fr/etherTypo/?id=989

+)   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%.

Hi Harry,

Exactly, these are the humidity classes which are programmed in OPAC according to the following table from the RAWMIC subroutine.

Output of subroutine RAWMIC with the following microphysical parameters.

================================================================================

RH COMP SIGMA RMOD RMIN RMAX MIXRAT VMIXRAT

================================================================================

0. inso 0.251E+01 0.471E+00 0.500E-02 0.200E+02 0.577E-04 0.320E-01

waso 0.224E+01 0.212E-01 0.500E-02 0.200E+02 0.100E+01 0.124E+00

50. inso 0.251E+01 0.471E+00 0.500E-02 0.200E+02 0.577E-04 0.205E-01

waso 0.224E+01 0.262E-01 0.600E-02 0.250E+02 0.100E+01 0.150E+00

70. inso 0.251E+01 0.471E+00 0.500E-02 0.200E+02 0.577E-04 0.168E-01

waso 0.224E+01 0.285E-01 0.640E-02 0.274E+02 0.100E+01 0.159E+00

80. inso 0.251E+01 0.471E+00 0.500E-02 0.200E+02 0.577E-04 0.142E-01

waso 0.224E+01 0.306E-01 0.670E-02 0.298E+02 0.100E+01 0.165E+00

90. inso 0.251E+01 0.471E+00 0.500E-02 0.200E+02 0.577E-04 0.102E-01

waso 0.224E+01 0.348E-01 0.710E-02 0.350E+02 0.100E+01 0.175E+00

95. inso 0.251E+01 0.471E+00 0.500E-02 0.200E+02 0.577E-04 0.710E-02

waso 0.224E+01 0.399E-01 0.740E-02 0.428E+02 0.100E+01 0.183E+00

98. inso 0.251E+01 0.471E+00 0.500E-02 0.200E+02 0.577E-04 0.437E-02

waso 0.224E+01 0.476E-01 0.780E-02 0.585E+02 0.100E+01 0.191E+00

99. inso 0.251E+01 0.471E+00 0.500E-02 0.200E+02 0.577E-04 0.317E-02

waso 0.224E+01 0.534E-01 0.790E-02 0.749E+02 0.100E+01 0.194E+00

================================================================================

Particle radii are given in um; dN/dlogr in particles/cm3; dV/dlogr in um3/m3; dM/dlogr in ug/m3; The radius interval dlogr = 0.01500.

Relative humidities are exactly as you cited.

Cheers,

Frank

As the developper of AEROgui, I appreciate your comments. Feel free to contact me if you have any comment/doubt at [email protected]

Roberto

Hi Frank, can you send me the code as well? My email address is [email protected].