Difference between the natural logarithm of surface roughness length for momentum and heat (or moisture) respectively. Theoretically the kB-1 should increase with the aerodynamic roughness of the surface due to the different mechanisms responsible for transfer of momentum and scalars like heat and moisture. Field measurements indicate that this is the case above low to medium rough surfaces like grass land and crops with kB-1≈2.3 (z0M/z0H=10) (Garrat, 1993). Sparse roughness elements also tend to enlarge the momentum transport compared to heat transport (Beljaars and Holtslag, 1991). However, kB-1 can be found to decrease above very rough forest surfaces due to a deep roughness sub-layer, which enhances the heat transport (Mölder et al 1999).
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0 |
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kB-1 |
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