Fig. 11. Dependence of the roughness parameter h on the volumetric water content _2,t measured at the 2-cm depth for the two periods ₁ and ₂ (solid lines). The dashed lines show h values for ₁ and ₂ averaged over the measured water content range. The calculated corresponding to h during ₁ or ₂ are indicated on the right axis. These values are of the same order as the optically measured values _opt shown in Table 1.