AN EQUIVALENT-OBSTACLE MODEL FOR COMPUTATION OF RADIATIVE FLUX IN OBSTRUCTED LAYERS

An idealized model is developed for considering the radiative effects in the atmospheric boundary layer due to the presence of natural or artificial obstacles located on the earth's surface. In the model, a set of such obstacles is simulated by an array of cylinders whose physical characteristics are used to derive formulas for the radiative flux and net radiation. Values of the net radiation then are plotted versus height for comparison with actual measurements within a corn crop canopy obtained by Allen et al. (1964). Parameters required by the model, but not directly measured in this particular set of observations, were obtained by fitting one measurement of the set at a single height and time. At most other heights and time, the numerical results provide a better fit to the empirical data than does an exponential approximation suggested by Allen. It is concluded that the derived formulas can adequately describe radiationheight distributions in this type of system, and that they would be particularly useful in pre-estimating the effects of variations in obstacle size and density by computer simulation. However, more observational data are needed to determine precisely the limitations of the model. © 1969.