= DIRECT vs DIFFUSE LIGHT accounting in ORCHIDEE =


This page will gather and summarise the activities around the merge of different initiative to account for Direct vs Diffuse light in ORCHIDEE for both energy related fluxes and photosynthesis activity or the emission of chemical species.

Three main developments that were done in this direction are:
 
 - A diagnostic implementation of Direct / Diffuse light for the Chemistry (BVOC) fluxes; Diagnostic in the sense that it does not modify the photosynthesis of ORC. Key persons are Juliette and Nicolas. Key papers are: Messina et al. (2016) see description in section 2.2 of the paper https://acp.copernicus.org/articles/16/14169/2016/acp-16-14169-2016.pdf. Palmira Messina worked at this time on updating and improving the BVOC emission scheme. Also see reference papers here:

 - The work of Yuan (branch: https://forge.ipsl.jussieu.fr/orchidee/wiki/GroupActivities/CodeAvalaibilityPublication/ORCHIDEE_DFv1.0_site) that is described in his paper [attachment:gmd-13-5401-2020.pdf Direct_Diffuse_YuanZhang]) that is very detailed and includes the impact on photosynthesis, transpiration as well as a scheme to compute the direct vs diffuse light from standard forcing with LMDZ.

 - The current Trunk of ORC with the work done in DOFOCO and the implementation of the 2-stream radiative transfert scheme of Pinty, which accounts for the effect of reflectance/transmittance at each canopy layer and thus to a certain extend of direct vs diffuse light. The article (not published) describing it is [attachment:gmd-2016-280.pdf 2Stream_Radiative_model] 

==> The overall objective of this task force is to possibly merge the different approaches in order to have only one schemes taking the best of existing developments.