Consideration of radiation absorption by stems in forests for microclimate modeling

Abstract. Forest canopy models are used to simulate biosphere–atmosphere coupling in global climate models, as well as the microclimate influences of forests at the stand scale. It has recently been shown that wood structures store significant heat following radiation absorption and impact air temperature diurnal patterns inside canopies. Yet, radiation absorption by woody stems is not fully considered in current models. Here we modify the radiative transfer component of the CanVeg2 multilayer canopy model to include radiation absorption by woody stems. We evaluate the model modifications by comparing estimates against a validated 3D ray tracing radiative transfer model parametrized using ground lidar measurements, and against tower observations of albedo in four broadleaf forests. We found a very good agreement between the 1D and 3D models, and a good agreement between models and observations. Our approach provides a tractable and computationally efficient implementation of radiation absorption by woody stems to calculate biomass heat storage in canopy models.