Modelling SIF in DART

[Meg Stretton]

Dear DART Team,

I am currently working with a DART scene with turbid vegetation, with user-defined optical properties, across the PAR wavelengths, using DART-FT to simulate the radiative budget. I would like to simulate the solar induced fluorescence of the scene, however I am stuck on how to do this, as I feel the numbers I am getting are too low.

I have set the Products to include the 'BRF/BTF Products', but within this I am unsure which exact product to choose - I believe this should be 'Radiance', but should I also select the 'Reflectance/Temperature'? Then, I select 'Fluorescence products' within the 'Optical and temperature properties' menu, and within each 'Volumes' phase function details, in the 'Prospect/Fluspect' menu I select 'Model' and 'Fluorescence'.

I am wondering if this is the correct way to set up DART to model the fluorescence? If so, I am wondering what the correct output files are for the simulated SIF, and what units these are in? Is DART able to simulate the SIF for each voxel, or is the only output an image of the SIF?

I am happy to send some example files if needed.

I look forward to hearing back from you,
Kind Regards,
Meg Stretton

[Omar Regaieg]

Dear Meg, 

It seems that you are on the good way for simulating the SIF using DART. 

For SIF images, we usually look at the 'Radiance' images. The units of these images are W.m^-2.µm^-1.sr^-1 

Yes, DART is able to simulate the SIF emission for each voxel. To get this product, you need to enable the radiative budget products, choose the unit  "W.m^-2.µm^-1 or  W.m^-2" and select the products you want. The SIF emission will be under "Emission" in the radiative budget products, in W.m^-2.µm^-1 units.  

Do not hesitate to send your simulation. I can help you set it up and give you some recommendations on how to improve it.

Best regards,

Omar Regaieg  

[Meg Stretton]

Hi Omar,

Thank you for your reply - it was really helpful to know which files to look at. I have put this work to the side, but I would really like to come back to it now, there are a couple of things that are still not quite right.

I am interested in getting the canopy-leaving SIF, ideally. Currently I have been looking at the 3D radiative budget files, as well as the images. It seems that the DART images are just the vertically integrated emission from the 3D radiative budget files. I am getting numbers that seem about an order of magnitude too large (~20) for this. I was wondering if this is to do with my viewing angle, my parameter choices, or maybe I am not looking at the correct thing?

I will upload my simulation and input text file, in case you think that would be helpful. If you have any insight into this then I would be really grateful!

Kind Regards,

Meg

[Omar Regaieg]

Hi Meg, 

The vertically integrated emission from the 3D radiative budget files, and the top of canopy SIF images are both possible DART products. I suspect that you might not be looking at the correct product. 

The canopy-leaving SIF in all directions can also be generated. 

It would be better if you send me your simulation, so I can I have a look at it. 

Best regards,

Omar