利用辐射换热角系数描述了非同温异质表面间的多次散射效应, 据此建立热辐射方向性模型, 并对模型的数值计算进行了讨论. 将模型应用于行结构目标, 结合孔隙率模型模拟其方向亮温(Directional Brightness Temperature, DBT)变化规律. 结果表明,模拟得到的规律与地面观测结果具有较高的一致性, 平均偏差在0.5 K以内. 同时发现, 多次散射效应增强了目标DBT, 但对DBT的变化幅度又起平滑作用; 目标组分的温差、 几何结构、 发射率均可导致DBT发生变化, 温差越大, 表面越凹, 发射率越小, DBT随观测角度变化的程度越剧烈; 模型可以解释热辐射中的"热点效应", 认为"热点"的产生主要与组分温度空间分布有关. 模型对于研究发射率方向性,城市热红外遥感反演及热红外邻近像元影响等问题可提供参考或思路.

The multiple scattering effect between heterogeneous non-isothermal surfaces is described rigorously using the configuration factor in engineering thermophysics. Based on the results a directional thermal radiance model is built, and the numerical calculation of the model is discussed. The model is integrated with the gap probability model and applied to a row structure to simulate the change of Directional Brightness Temperature (DBT). The results show that the modeled DBT agrees well with the observed DBT, especially under the condition that the gap probability is very low. It is also shows that the DBT is aggrandized because of the multiple scattering effects, whereas the change of DBT tend to average out. The temperature difference, spatial distribution, emissivity of the components can all lead to the change of DBT. That is to say, the higher of the temperature difference, the craggier of the surface and the lower of the emissivity, the more exquisite DBT changes along with the viewing zenith. The model developed in this paper can explain "hot spot effect" of thermal radiance, and it is confirmed that the existence of "hot spot" is mainly related to the spatial distribution of components' temperature. This model can be used for the study of directional effect on emissivity, the LST retrieval over urban areas and the adjacency effect of thermal remote sensing pixels.