Sensitivity of Modeled Leaf Temperature to Canopy Radiative Transfer Formulations

Neglecting the spectral nature of in-canopy sunlight transfer can lead to substantial uncertainties in the estimation of foliage temperature and photochemical reactions because interactions with canopy elements change the light spectrum shape. Due to the strong wavelength dependence in green leaf optical properties, different wavelength regions are attenuated differently in plant canopies. Such modifications to the light spectrum shape can also lead to errors in the estimation of leaf temperature if only a few broad bands are considered in radiative transfer models because leaf absorptivity and reflectivity are wavelength dependent. Results from a new one-dimensional model are used to evaluate the sensitivity of leaf temperature to different formulations of radiative transfer in plant canopies. The impacts of leaf temperature errors on the calculations of sensible heat flux density, canopy energy balance, and emissions of biogenic volatiles are examined. The fidelity of the modeled convective boundary layer depth is evaluated due to uncertainties in the surface sensible heat flux. Results also indicate that using only broad bands in-canopy radiative transfer calculations to estimate the decomposition of molecules amenable to undergo photolysis can give daily integrated errors in photolysis frequency of up to 25 %, depending on the reaction of interest and radiative transfer formulations used in the model.