Surface renewal estimates of evapotranspiration. Short canopies.

Surface renewal (SR) analysis was utilized to calculate sensible heat flux density (H) over pasture grass, wheat, and sorghum canopies. The SR analysis uses high frequency temperature measurements above canopies to calculate H values using a conservation of energy equation. Then the H values were employed to estimate evapotranspiration (lE) using net radiation and soil heat flux density in the energy balance equation. The results were compared with lE values calculated using an independent measurement of H obtained with a sonic anemometer. Good estimates were found without the need for a weighting factor to account for unequal heating of the air volume below each measurement height. When a weighting factor was included in the calculation of H, the SEE values were improved. In combination with measurements of net radiation and soil heat flux density, the surface renewal method showed promise as a low-cost method to estimate evapotranspiration.