The concept of effective emissivity of nonisothermal mixed pixel and its test

Based on two preconditions, the local thermal equilibrium is satisfied and emissivities do not change with temperature, the concept of component effec tive emissivity of nonisothermal mixed pixel has been put forward and then the radiant directionality model of nonisothermal mixed pixel constructed f rom it. Our study shows that the component effective emissivity is associat ed with geometric structure, optical properties of target, and viewing angl e, but does not depend on the component temepratures. The component tempera tures can only change the ratio of component radiance to the total radiance of the mixed-pixel. The total effective emissivity of this pixel is the co mplement of its directional-hemisphere reflectance. After the simulation of component effective emissivity of the discrete cones and continuous vegeta tion canopy (winter wheat) by the Monte Carlo method, our model of radiant directionality of nonisothermal mixed pixel have been proved by lab and fie ld measurements.