Evaporation from multi-component canopies: Generalized formulations

A general formulation is derived for expressing the evaporation from multi-component canopies representing mixed-plant communities. It generalizes to n components the formulations introduced by Lhomme et al. (Bound-Layer Meteorol. 144, 243–262, 2012) for two and three components models. The new formulation is an alternative and simpler form of the equations previously developed by Wallace (Q. J. R. Meteorol. Soc. 123, 1885–1905, 1997). It is sounder, in the sense that: (i) it accounts for the impact of stomatal characteristics (hypostomatous or amphistomatous) on evaporation expression; (ii) it allows one to eliminate the confusing “Penman–Monteith” type terms of Wallace’s formulation (which do no not represent the individual component evaporations). Additionally, the steps of the mathematical demonstration are clearly specified, which was not the case for Wallace’s formulation. In this way, a general conceptual framework is defined for evaporation from complex vegetation, from which simpler representations (1, 2 or 3 components models) and asymptotic limits (infinite identical components) can be inferred.