ESTIMATION OF SENSIBLE HEAT-FLUX FROM REMOTELY SENSED CANOPY TEMPERATURES

Temperatures of tallgrass prairie vegetation were measured with infrared thermometers (IRT) at different view zenith and azimuth angles. The optimum IRT view zenith angle for estimating sensible heat fluxes (H) was determined by comparing H estimated with eddy correlation and/or Bowen ratio techniques to H calculated by a method suggested by Hatfield et al. (1984). For wind speeds of 5 m s-1 or greater, H estimated with surface temperatures measured at a 0-degrees or 20-degrees view zenith angle gave the best agreement, but for wind speeds of less than 4 m s-1 the best estimate of H was made with surface temperatures measured at a 40-degrees or 60-degrees view zenith angle.