===== Benchmark dataset for UV-Vis-NIR spectral regions=====


==== Monochromatic calculations ====


Calculations were performed for all combinations of the following parameters: 

//Wavelengths//: 325nm, 450nm, 765nm, 1700m\\
//Viewing angle range//: 0° - 60°, 5° increment\\
//Solar zenith angles//: 0°, 30°, 60°, 80°\\
//Solar azimuth angles//: 0°, 40°, 150°, 220°\\
//Surface albedos//: 0, 0.2, 0.8\\


Each case was computed for the following scenarios with and without polarization.\\
Output: Normalized radiance (I Q U V)/E_0

=== Clear sky (Rayleigh scattering) ===

Rayleigh scattering coefficients were computed according to Bodhaine 1999, Eq. 29 for a 100 layer equidistant model atmosphere (US Standard, Anderson 1986). The following files include the coefficients as calculated on the 101 levels or averaged for the 100 model layers: 
{{:studies:esaslight2:uvvisnir:csca_rayleigh_layer.dat|}}\\
{{:studies:esaslight2:uvvisnir:csca_rayleigh_level.dat|}}

The Rayleigh scattering matrix is well known: 

{{ :studies:esaslight2:uvvisnir:rayleigh_matrix.png?300 | Rayleigh scattering matrix (from Emde et al., 2010). θ is the scattering angle and δ the depolarization factor.}}

θ is the scattering angle and δ the depolarization factor, which is also calculated from Bodhaine 1999: 
{{:studies:esaslight2:uvvisnir:depol.dat|}}

== Vector calculations ==
The following plots show the results of all vector calculations: 
{{:studies:esaslight2:uvvisnir:results_comparison.pdf|}}\\
Lines correspond to the SCIATRAN results and crosses to MYSTIC results. The results agree within the Monte Carlo noise (<0.5% for I, <1% for Q, U, V is zero for Rayleigh scattering).  

The SCIATRAN results (analytical) may be used as benchmark, we do not provide MYSTIC results because of Monte Carlo noise.\\
Benchmark data (SCIATRAN): {{:studies:esaslight2:uvvisnir:st_rayleigh.nc|}}

== Scalar calculations ==
Plots: {{:studies:esaslight2:uvvisnir:results_comparison_scalar.pdf|}}\\
Lines correspond to the SCIATRAN results and crosses to DISORT results. The agreement is better than 0.005%.\\
Benchmark data (DISORT): {{:studies:esaslight2:uvvisnir:result_rayleigh_scalar.nc|}}

=== Clear sky (Rayleigh scattering + absorption) ===

In a real atmosphere the molecules also absorb radiation, the next scenarios are for a realistic molecular atmosphere including scattering and absorption. The absorption coefficients are calculated using the libRadtran model which includes absorption coefficients of all relevant atmospheric species. For 1700 nm the absorpion parameterization based on representative wavelengths (Gasteiger et al 2013) was used:\\
{{:studies:esaslight2:uvvisnir:cabs_mol_level.dat|}}\\
{{:studies:esaslight2:uvvisnir:cabs_mol_layer.dat|}}

The agreement of the models is similar to the cases without absorption.
 
== Vector calculations ==

Plots: {{:studies:esaslight2:uvvisnir:results_absorption.pdf|}}\\
Benchmark results (SCIATRAN): {{:studies:esaslight2:uvvisnir:st_rayleigh_abs.nc|}}

== Scalar calculations ==

Plots: {{:studies:esaslight2:uvvisnir:results_absorption_scalar.pdf|}}\\
Benchmark results (DISORT): {{:studies:esaslight2:uvvisnir:result_rayleigh_abs_scalar.nc|}}


=== Cloud   (water cloud, optical properties provided) ===

Cloud in 2-3 km altitude, optical thickness: 10

Optical properties are provided in the following files: 

netcdf-Format:
{{:studies:esaslight2:uvvisnir:wc_325.mie.cdf|}}
{{:studies:esaslight2:uvvisnir:wc_450.mie.cdf|}}
{{:studies:esaslight2:uvvisnir:wc_765.mie.cdf|}}
{{:studies:esaslight2:uvvisnir:wc_1700.mie.cdf|}}

ascii-Format:
{{:studies:esaslight2:uvvisnir:wc_325.mie.dat|}}
{{:studies:esaslight2:uvvisnir:wc_450.mie.dat|}}
{{:studies:esaslight2:uvvisnir:wc_765.mie.dat|}}
{{:studies:esaslight2:uvvisnir:wc_1700.mie.dat|}}

The variable "phase" includes the phase matrix, as a function of the
scattering angle (variable "theta"). The 4x4 scattering phase matrix for spherical
droplets has four non-zero elements, which are stored in the following order:

| P1 | P2 | 0  | 0  |
| P2 | P1 | 0  | 0  |
| 0  | 0  | P3 | P4 |
| 0  | 0  | -P4| P3 |

The single scattering albedo and the extinction coefficient are also
stored in the files.


Plots: {{:studies:esaslight2:uvvisnir:results_cloud_noabs.pdf|}}\\
Benchmark results (SCIATRAN): {{:studies:esaslight2:uvvisnir:st_cld.nc|}}
	    
==== High spectral resolution calculations ====

=== O2A band (755 - 775 nm) (clear) ===

The absorption coefficients in the O2A band have been calculated for the midlatitude-summer atmosphere using the [[http://www.sat.ltu.se/arts/|ARTS]] model. They are based on the HITRAN2004 line cataloque. 

As input the absorption coefficients {{:studies:esaslight2:uvvisnir:abs_coeff_lbl_o2a.dat|}}
or alternatively the absorption optical thicknesses of each model layer {{:studies:esaslight2:uvvisnir:moltau_o2a.nc|}}
may be used.

The spectra are calculated for all viewing geometries and solar zenith angles defined above. The surface albedo was constantly 0.2.

Plots: {{:studies:esaslight2:uvvisnir:results_absorption_spectra.pdf|}}\\

Benchmark results (SCIATRAN): {{:studies:esaslight2:uvvisnir:st_o2_spec.nc|}}