SIMULATED CANOPY MICROCLIMATE USING ESTIMATED BELOW-CANOPY SOIL SURFACE TRANSFER-COEFFICIENTS

Numerical models are often used to simulate the complex energy and mas s transfer processes in soil-plant-atmosphere systems. The objective o f this study was to develop relationships from measurements of interfa cial transfer coefficients at the soil surface beneath a plant canopy to improve a numerical model describing within-canopy energy and mass transfer processes. Equations based on dimensionless variables are pre sented that predict interfacial heat and water vapor transfer coeffici ents at the soil surface beneath a maize (Zea mays L.) canopy througho ut a growing season. The derived relationships include the effects of surface roughness, the scale of turbulent eddies, and turbulence inten sity. The equation for interfacial heat transfer coefficients was inco rporated into the comprehensive soil-plant-atmosphere model Cupid wher e it was used to estimate heat and mass transfer coefficients at the s oil surface. Comparison of model predicted and measured canopy microcl imate characteristics showed that the new formulation produced transfe r coefficients that were more consistent and more closely correlated t o within-canopy wind speed than those obtained by three estimation tec hniques used in the model previously. The new transfer coefficient rel ationship generally improved model predictions and has the advantage o f being based on more direct experimental evidence than previous relat ionships.