Modelling directional brightness temperature over a urban areas with simplified geometrical structure

A modelling study on the hemispherical variations of directional brightness temperature (DBT) for row-structured building arrays was carried out based on the ground observations over a residential in urban areas. The model assumes that the DBT is a function of component brightness temperatures and their directional fractions. Their fractions in the scene depend on sun-view geometry and the geometry of buildings. The methodology for brightness temperature component classification and temporal variations of component values were analyzed based on the experiment dedicated to urban brightness temperature distribution. Results reveal that the number of typical objects of an urban area and their brightness temperature values vary with time of day due to the complex of urban thermal feature and geometrical structures. Generally, the trend of brightness temperature variation is similar for asphalt road and concrete place, grass and trees, walls of the building toward different directions, and the windows of the walls. In the simulation of urban areas hemispherical DBT, the results reveal an evident row-direction-oriented stripe in DBT polar map, where no hot spot appears. As an initial attempt, the research only focus on the simplified conditions, more complicated structure may be considered in the further researches.