Transfer characteristics for a heterogeneous surface of large aerodynamic roughness



Values of zo and ZT, roughness scaling lengths for momentum and heat, are found to be 0.4±0.2m and 0.035±0.02m, respectively, for a heterogeneous surface comprising 8m high trees with transpiring foliage, 1 m high dry grass, and sandy soil. Determination of ZT utilizes aircraft and ground-based radiometric observations of surface temperature.

The ratio Zo/ZT ≈ 12 was found essentially constant over the observed roughness Reynolds number range 5000–25000, consistent with values published for homogeneous natural vegetated surfaces.