A refinement to the two-leaf model for calculating canopy photosynthesis

The two-leaf model developed by Wang and Leuning (1998) [A two-leaf model for canopy conductance, photosynthesis and partitioning of available energy I. Model description and comparison with a multi-layered model. Agric. For. Meterol. 91, 81–111] usually overestimates the hourly photosynthesis, latent heat flux and canopy conductance of sunlit leaves, and underestimates the hourly sensible heat fluxes compared to a more detailed multi-layer model. In all cases errors on average were <5%. Here I present a refinement to the two-leaf model that reduces discrepancies between the two-leaf and multi-layered models to <3% while increasing by less than 1% the computing time required when the two-leaf model is used as the surface scheme in a climate model.