Computing the light extinction of a forest scene

[Anne Baranger]

Dear DART team,

I am using DART 5.10.9 to simulate the radiative budget of a voxelised forest scene. I believe I have successfully built the scene geometry and generated 3D radiative budget outputs, but I am unsure about the interpretation of some parameters and outputs.

My objective is to derive light extinction profiles within the canopy, in order to characterise how incoming solar radiation is absorbed by the forest.

To do so, I am currently using the 3D radiative budget output (ITERX) and focusing on the variable TotalEntry, which I understand corresponds to the irradiance entering each voxel.

However, when analysing the results, I observe that  TotalEntry values above the canopy are zero, whereas I expected non-zero values corresponding to direct solar radiation transmitted from above the scene (see attached figure).

Could you please clarify:

1. Whether TotalEntry is the appropriate variable to use for estimating vertical light extinction in a voxelised canopy?

2. Why  TotalEntry above the canopy might be zero ? is this because of the way I have parametrised my simulation?

I have attached my full simulation folder in case it helps to diagnose how the simulation is parameterised.

Thank you very much for your help.

Best regards,
Anne Baranger

[Anne Baranger]