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DiffIlluminav1v2

In this document we will try to give some comparizon of the two versions of the Illumina model.

Feature v1 v2
Resolution Fixed to 1km with some degradation with distance Multilayer/Multiscale from 20m
Point spread function with 1st scattering only
Point spread function with 2nd scattering
Radial comparizon v1 v2
Single scattering

1st and 2nd order of scattering
Line of sight Voxels sticked to a fixed 3D grid (1km x 1km x dz) Mini voxels of 1m3 with an initial resolution of 19m with a multiplicative factor of 1.12
Modeling grid fixed horizontal grid (1 km) plus a fixed exponential vertical grid No vertical grid for the line of sight but fixed resolution grid for the calculation of the 2nd order of scattering. That grid is centered on the mean position between the lamp and the line of sight point and is approching a sphere in shape with a resolution of 2.5km. The maximal allowed height is either 35km or the cloud base height.
Ground reflectance Variable on each grid point according to the reflectance product of MODIS Fixed all over the domain but obtained by combining some typical surface reflectance spectra
Overhead clouds Fixed cloud base height per cloud type. Cloud type to be defined by user. Cloud base height and cloud type both defined by the user separatly.

Cloud fraction introduced
Topography screening - Improved horizon blocking scheme
Scattering probability - Completly new and more accurate scattering probability equations
Extinction - Completly new and more accurate transmission equations
Solid angles calculations Using the coarse fixed 3d grid of the model and some approximations depending of the viewing angle and the vertical layer thickness. Accurate calculation using a unity 1m3 volume
Separated cloud radiance printout Cloud radiance not separated from the total radiance The radiance from clouds and the total radiance is given in the output file
Adding the calculation of the direct radiance radiance No direct radiance considered Direct radiance both from lamps and from refleting surfaces
Line of sight below horizon Minimum elevation angle of 0.5 deg Any elevation angle allowed
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Page last modified on October 28, 2020, at 02:11 pm UTC