Radiative Transfer Model 3.0 integrated into the PALM model system 6.0

Abstract. The Radiative Transfer Model (RTM) is an explicitly resolved three-dimensional multi-reflection radiation model integrated in the PALM modelling system. It is responsible for modelling of complex radiative interactions within the urban canopy and it represents a key component of modelling of energy processes inside the urban layer, and consequently PALM's ability to provide explicit simulations of urban canopy in meter-scale resolution. This paper describes RTM version 3.0 which is integrated in PALM modelling system version 6.0. This version of RTM has been substantially improved over previous versions with new simulated processes, providing a more realistic representation of a wider range of urban scenarios, as well as with new discretization schemes and algorithms for a significantly better scalability and computational efficiency, enabling larger parallel simulations with up to many thousands of parallel processes.