SURFACE RENEWAL ANALYSIS FOR SENSIBLE HEAT-FLUX DENSITY USING STRUCTURE FUNCTIONS

Surface renewal (SR) analysis was used to estimate the sensible heat f lux density (H) over different crop canopies (grass, wheat and sorghum ) and the results were compared with eddy covariance measurements. Hig h-frequency temperature traces showed ramp-like structures, and struct ure functions were used to determine the mean amplitude and duration o f these ramps. The ramp characteristics were used to estimate H. A wid e range of sensible heat flux density conditions were observed. The ac curacy was acceptable, but was dependent on the measurement height, th e wind shear at the measurement lever, and the time lags used in the s tructure functions. The use of surface renewal H values in energy bala nce determination of lambda E can give results nearly as accurate as t hose obtained using a sonic anemometer. (C) 1997 Elsevier Science B.V.