Importance of radiative transfer processes in urban climate models: a study based on the PALM 6.0 model system

Abstract. Including radiative transfer processes within the urban canopy layer into microscale climate models (UCMs) is essential to obtain realistic model results. These include interaction of buildings and vegetation with shortwave longwave radiation, thermal emission, radiation reflections. They contribute differently budget surfaces. Each process requires different computational resources physical data for elements. This study investigates how much detail modellers should parameterize in building-resolving UCMs. To that end, we introduce a stepwise parameterization method Parallelized Large-eddy Simulation Model (PALM) system 6.0 quantify individually effects main on flow field. We numerical simulations both simple configurations identify major minor budget. The shows such as surface will have effects, while multiple reflections effects. also implicitly affect incoming since coupled model. field changes considerably response included identified those which are essentially needed assure acceptable quality receiving from atmosphere based sky-view factors, among surfaces, considering at least single reflection radiation. Omitting any these may lead high uncertainties