Comparison of Aerodynamic Characteristics among Boreal, Cool-temperate and Warm-temperate Forests

Zero-plane displacement d and roughness length z0 were compared among boreal, cool-temperate, and warm-temperate forests. The normalized zero-plane displacement d/h (where h is the tree height) increased with stand density, whereas z0/h decreased. On the other hand, d/h showed a negative correlation with plant area index (PAI), which was inconsistent with parameterization of the models. The effect of the vertical structure of the forest might be included in PAI. Seasonal variations of d/h were observed in cool-temperate and warm-temperate forests. d/h decreased from autumn to winter in these sites which corresponded to the fall of leaves. However, d/h was underestimated by the models, and the decrease in d/h for cool-temperate forest appeared to be small compared with that predicted using the models with the large decrease in PAI.