Estimation of sensible heat flux from remotely sensed surface temperatures.

Abstract

A series of energy-balance experiments were performed over a winter wheat field in Southern Arizona. A Bowen ratio energy-balance system (BREB), anemometer, and thermal infrared thermometer (IRT) were placed in the center of the field on day 15 of 1988 shortly after germination. The BREB system generated 12-minute averages of net radiation, soil heat flux, latent energy, and sensible heat flux (H) throughout the season, terminating on day 152, just before harvest. On day 134, an eddy-correlation system was placed adjacent to the BREB system, where it collected H-data concurrently for 17 successive days. The data from the BREB and eddy-correlation systems were regressed against each other to quantify their field performance. The regression standard error (SE) between the two systems was ±40 W/m². BREB H-data was used as a "standard" to evaluate three different sensible heat flux models that are suitable for remote sensing applications. The three models require thermal canopy temperature, air temperature, and wind speed as input. Two of the three models use aerodynamic resistance theory, one of which is stability corrected, and the third remote-sensing model employs Monin-Obukhov turbulent transfer theory. The regression analysis between the BREB H-values and the three remote-sensing models shows that the stability corrected aerodynamic resistance model and the Monin-Obukhov model are capable of estimating H-values over a wide range of surface and atmospheric conditions.