Reptran has much more molecules than the (very) old LOWTRAN. I strongly encourage you to use the reptran option.

Thank you dear sir Govaerts for your answer.

This is an example of input parameters to compute GHI, BHI and DHI for zout = 0 and for zout = Top Of the Atmosphere (for verification purpose) under clear sky condition (no clouds) with libRadtran 2.0beta

In this example, libRadtran-2.0-beta is installed at this path /libradtran

A specific type of aerosol has been chosen in the OPAC library

Considering the input file in.par

rte_solver fdisort2

data_files_path /libradtran/libRadtran-2.0-beta/data/

atmosphere_file /libradtran/libRadtran-2.0-beta/data/atmmod/afglt.dat

source solar /libradtran/libRadtran-2.0-beta/data/solar_flux/kurudz_1.0nm.dat

aerosol_default

mol_abs_param kato2

wavelength 241 4605

number_of_streams 16

sza 45.000000

day_of_year 170

mol_modify O3 200.000000 DU

mol_modify H2O 20.000000 MM

aerosol_set_tau_at_wvl 500 0.2

aerosol_species_library OPAC

aerosol_species_file maritime_tropical

albedo 0.100000

altitude 0

zout 0.000000 toa

output_process sum

output_user zout eglo edir edn

quiet

The output of the command line "./uvspec < in.par" is in this specific case is then:

0.000000 7.055665e+02 5.284130e+02 1.771535e+02

120.000000 9.343168e+02 9.343218e+02 -5.005445e-03

Dear mr Blanc,

thank you very much for your contribution.

I 'm really troubled cause I see a 10% reduction in the ratio measured to modeled GHI within ~0-0.6 aod@500 and I don't know how to fix it.

I take into account real aod measurements as an input and H2O too but I can't get this dependence out of the picture...

the input file looks like the following:

atmosphere_file ../data/atmmod/afglmw.dat

source solar ../data/solar_flux/kurudz_1.0nm.dat

albedo 0.3

rte_solver disort

pseudospherical

mol_abs_param reptran medium

deltam on

number_of_streams 6

day_of_year 274

sza 44.242

aerosol_default

altitude 0.06

wavelength 290 4500

mol_modify O3 274.61 DU

mol_modify H2O 22.8625 MM

aerosol_modify ssa scale 0.85

aerosol_angstrom 1.3 0.064379

aerosol_modify gg set 0.70

spline 291 4499 1

output_user lambda eglo

quiet

Should I use Kato2? Change the solver? Pfuff...

Any ideas?

Thank you in advance.

Melina.