1998 Volume 11 Issue 3 Pages 221-228
A forest model based on an all-sky photograph was used to investigate the effects of tree height and distance between trees on the total sky view factor (P), the sun path sky view factor (Q) and the relationships between P and Q of a coniferous forest and a deciduous forest with no leaves. Variations in Q owing to the direction of a forest were also evaluated. P and Q are important factors for discussing the transmission of radiation to the forest floor, because P represents the transmissivity of diffuse radiation and Q represents the transmissivity of direct radiation. For both types of forest, P and Q became larger as the tree height became lower and the distance between trees became larger. Tree height especially affected Q of the coniferous forest, and distance between trees affected P of both coniferous and deciduous forests. The relationships between P and Q varied according to type of forest, and Q of the deciduous forest was smaller than that of the coniferous forest for the same value of P. The value of Q of the coniferous forest depended mainly on the position of the nearest tree to the observation point. Forest direction strongly affected Q of the coniferous forest when P∼0.5 but only affected Q of the deciduous forest.
