Measuring sensible heat flux density over pasture using the C-T(2)-profilemethod

Two large-aperture infrared scintillometers were positioned at heights (z) of 10 and 1.5 m with beams propagated horizontally over pasture for distanc es of 3.1 km and 141 m, respectively. From each scintillometer a half-hourl y average value of the path-averaged, temperature-structure parameter (C-T( 2)) was obtained in unstable atmospheric conditions. The result suggested C -T(2) to scale with height as z(-2/3). Using the C-T(2)-profile method a pa th-averaged measure of the Obukhov length (L-0) was calculated for each hal f-hour period, whence L-0 was used to determine the friction velocity, u(*) and the surface-layer temperature scaling parameter, T-*. The scintillomet er-based sensible heat flux density H-sc was then calculated from H-sc = rh o C(p)u(*)T(*). A time series of half-hourly averaged H-sc compared to H-ec obtained by the eddy covariance method agreed to within 10%, with R-2 = 0. 67, for a range of unstable conditions (-0.2 less than or equal to z/L-0 le ss than or equal to -0.01).