Impacts of Different Components' Proportion Determination Methods on Directional Brightness Temperature Simulation for Urban Targets

Directional brightness temperature(DBT) plays an important role in surface energy balance and urban climate.Determination of components' proportion is one of the key factors to accurate simulation of DBT.An overview of the main components' proportion determination methods used currently on urban surfaces was unfolded and some techniques utilized in row crops were expanded to adapt three-dimensional urban targets,achieving radiosity method,horizontal projection method,oblique projection method and center projection method.Comparison between those above-mentioned four components' proportion determination methods demonstrate that they simulate the spatial distribution of DBT perfectly when the zenith angle is small.The result also shows that it is feasible to compute the components' proportion through sketching and calculating on the photograph filmed by a digital camera located near the thermal infrared sensor(center projection method).However,the horizontal projection method is an exception,which has a low precision corresponding to DBT when the zenith angle increased or differences between components' temperature extended to a higher level.Finally,a comparative study was conducted on simulation accuracies and complexities of different methods and some specific recommendations were given for diverse needs.