Sensitivity of the GEM Model to Different Descriptions of City Surface Parameters over Warsaw

Abstract

Over half of the world’s population lives in urban areas, even though urban agglomerations cover only 0.05% of the Earth’s surface. Urbanisation significantly modifies the surface level’s moisture, radiation balance, thermal stability, and aerodynamic properties. The physical processes in the urban surface layer directly influence the atmosphere above and, specifically, the atmospheric boundary layer. Thus, understanding and modelling these processes are necessary for studying the urban meteorology. The primary objective of the presented research was to assess the impact of the urban land cover on the development of the atmospheric boundary layer over Warsaw. To carry out the objective, a high-resolution version of the Global Multiscale Environmental model was used to examine its ability to reproduce the diurnal cycle of the meteorological parameters, including the thermal and turbulent structure of the atmosphere. The Town Energy Balance (TEB) parameterisation was used to represent urban effects on modelled meteorological parameters at the final nesting level with a horizontal resolution of 1 km over Warsaw. Mid-high buildings, sparse buildings, industrial areas, roads and parking spaces, and a mix of built and nature are the urban cover categories used in the TEB parameterisation. Four one-day cases representing different meteorological conditions and seasons were selected for modelling.