The spatial variability of turbulence above a forest

The spatial variability of turbulence above a forest has been examined. Two measurement towers were erected 800 m apart within a heterogeneous mixed f orest located in the north east of the Netherlands. The measurements of u*/ u were analysed and subsequently used to test a surface layer model. The mo del simulated the magnitude of the measurements reasonably well, but measur ed trends were not always reproduced by the model. The variable (du/dz)/u d id not adapt as quickly to the new surface as u*/u. This is in agreement wi th Schmid (1994), and can be explained by a local decrease in mixing length . It is recommended to adapt the mixing length near a surface transition to improve the accuracy of surface layer models of heterogeneous landscapes.