ESTIMATION OF SURFACE STRESS OVER A FOREST FROM SODAR MEASUREMENTS AND ITS USE TO PARAMETERIZE THE STABLE BOUNDARY-LAYER HEIGHT

Sodar observations from three nights of the HAPEX-MOBILHY experiment h ave been used to compute covariances between single measurements of th e three velocity components. From these, estimates of a low frequency friction velocity u are derived which show better correlation with ob served values of the stable boundary layer (SBL) height, h, than direc t u-measurements by an ultrasonic anemometer. On the contrary, interd iurnal variability of h is better correlated with direct u-measuremen ts. These findings should be mainly due to the problem of different sp ectral and spatial representativity of the two u-values.