STUDY ON DIURNAL-VARIATION OF BULK DRAG COEFFICIENT OVER DIFFERENT LANDSURFACES

The magnitude and diurnal change of turbulent bulk drag coefficients o ver land have been analysed using mean velocity and temperature gradie nt data of the planetary boundary layer. The turbulent drag coefficien ts can be about an order of magnitude larger over the rough land surfa ce than over the sea surface. We computed these coefficients by the sa me method for three typical underlying surfaces represented by urban, grassland and Gobi desert. The results show that there are significant differences in the turbulent transfer among the three typical underly ing surfaces.