A new urban surface model integrated in the large-eddy simulation model PALM
Jaroslav Resler1,2, Pavel Krč1,2, Michal Belda1,2,4, Pavel Juruš1,2, Nina Benešová1,3, Jan Lopata1,3, Ondřej Vlček1,3, Daša Damašková1,3, Kryštof Eben1,2, Přemysl Derbek1, Björn Maronga5, and Farah Kanani-Sühring51Faculty of Transportation Sciences, Czech Technical University in Prague, Czech Republic 2Institute of Computer Science, The Czech Academy of Sciences, Prague, Czech Republic 3Air Quality Protection Division, Czech Hydrometeorological Institute, Prague, Czech Republic 4Department of Atmospheric Physics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic 5Institute of Meteorology and Climatology, Leibniz Universität Hannover, Hannover, Germany
Received: 09 Mar 2017 – Accepted for review: 14 Mar 2017 – Discussion started: 15 Mar 2017
Abstract. Urban areas are an important part of the climate system and many aspects of urban climate have a direct effect on human health and living conditions. This implies the need for a reliable tool for climatology studies that supports urban planning and development strategies. However, a realistic implementation of urban canopy processes still poses a serious challenge for weather and climate modelling for the current generation of numerical models. To address this demand, a new model of energy processes for urban environments was developed as an Urban Surface Model (USM) and integrated as a module into the large-eddy simulation (LES) model PALM. The USM contains a multi-reflection radiation model for short and long wave radiation, calculation of the energy balance on horizontal and vertical impervious surfaces, thermal diffusion in ground, wall and roof materials and anthropogenic heat from transportation. The module also models absorption of radiation by resolved plant canopy (i.e. trees, shrubs). The USM was parallelized using MPI and performance testing demonstrates that the computational costs of the USM are reasonable and the model scales well on typical cluster configurations. The module was fully integrated into PALM and is available via its online repository under GNU General Public License (GPL). The implementation was tested on a summer heat wave episode in the real conditions of a selected Prague crossroad. General patterns of temperature of various surface types (walls, pavement) are in good agreement with observations. The coupled LES-USM system appears to correct the bias found between observations and mesoscale model predictions for the near-surface air temperature. The results, however, show a strong dependence on the prescribed surface and wall material properties. Their exact knowledge is thus essential for the correct prediction of the flow in the urban canopy layer.
Resler, J., Krč, P., Belda, M., Juruš, P., Benešová, N., Lopata, J., Vlček, O., Damašková, D., Eben, K., Derbek, P., Maronga, B., and Kanani-Sühring, F.: A new urban surface model integrated in the large-eddy simulation model PALM, Geosci. Model Dev. Discuss., doi:10.5194/gmd-2017-61, in review, 2017.