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 have been used to compute covariances between single measurements of the three velocity components. From these, estimates of a low frequency friction velocity u* are derived which show better correlation with observed values of the stable boundary layer (SBL) height, h, than direct u*-measurements by an ultrasonic anemometer. On the contrary, interdiurnal variability of h is better correlated with direct u*-measurements. These findings should be mainly due to the problem of different spectral and spatial representativity of the two u*-values.