This version of ORCHIDEE has been used in publication "Modeling the impacts of diffuse light fraction on photosynthesis in ORCHIDEE (v5453) land surface model" by Zhang et al to be submitted to GMD. Reference and information will be added later << Reference to be added as soon as the manuscript is available >>.


Aerosol and cloud-induced changes in diffuse light have important impacts on the global land carbon cycle by changing light distribution and photosynthesis in vegetation canopies. However, this effect remains poorly represented in current land surface models. Here we add a light partitioning module and a new canopy light transmission module to the ORCHIDEE land surface model (trunk version, v5453) and use the revised model, ORCHIDEE_DF, to estimate the fraction of diffuse light and its effect on gross primary production (GPP) in a multi-layer canopy. We evaluate the new parameterizations using flux observations from 159 eddy covariance sites over the globe. Our results show that compared to the original model, ORCHIDEE_DF improves the GPP simulation under sunny conditions and captures the observed higher photosynthesis under cloudier conditions in most plant functional types (PFTs). Our results also indicate that the larger GPP under cloudy conditions compared to sunny conditions is mainly driven by increased diffuse light in the morning and in the afternoon, and by decreased VPD and air temperature at midday. The observations show strongest positive effects of diffuse light on photosynthesis are found in the range 5-20 °C and VPD<1 kPa. This effect is found to decrease when VPD becomes too large, or temperature falls outside that range likely because of increasing stomatal resistance to leaf CO2 uptake. ORCHIDEE_DF underestimates the diffuse light effect at low temperature in all PFTs and overestimates this effect at high temperature and high VPD in grasslands and croplands. The new model has the potential to better investigate the impact of large-scale aerosol changes on the terrestrial carbon budget, both in the historical period and in the context of future air quality policies and/or climate engineering.

Code access


DOI [under request]
Creator Yuan ZHANG
Affiliation LSCE
Title ORCHIDEE_DFv1.0_site
Publisher Institut Pierre Simon Laplace (IPSL)
PublicationYear 2020
ResourceType Software
Rights This software is distributed under the CeCILL license
Subject Canopy light transmission, Land surface model, terrestrial carbon cycle
DataManager Karim Ramage (IPSL)
DataCurator Josefine Ghattas (IPSL)
ContactPerson Yuan Zhang (LSCE)
FundingReference The IMBALANCE-P project of the European Research Council (ERC-2013-SyG- 610028); ANR CLAND Convergence Institute

Last modified 6 months ago Last modified on 12/06/21 09:24:25