Evaluating the urban canopy scheme TERRA_URB in the COSMO model for selected european cities

The increase in built surfaces constitutes the main reason for the formation of the Urban Heat Island (UHI), that is a metropolitan area significantly warmer than its surrounding rural areas. The urban heat islands and other urban-induced climate feedbacks may amplify heat stress and urban flooding under climate change and therefore to predict them correctly has become essential. Currently in the COSMO model, cities are represented by natural land surfaces with an increased surface roughness length and a reduced vegetation cover, but this approach is unable to correctly reproduce the UHI effect. By increasing the model resolution, a representation of the main physical processes that characterize the urban local meteorology should be addressed, in order to better forecast temperature, moisture and precipitation in urban environments. Within the COSMO Consortium a bulk parameterization scheme (TERRA_URB or TU) has been developed. It parametrizes the effects of buildings, streets and other man-made impervious surfaces on energy, moist and momentum exchanges between the surface and atmosphere, and additionally accounts for the anthropogenic heat flux as a heat source from the surface to the atmosphere. TU implements an impervious water-storage parameterization, and the Semi-empirical Urban canopy parametrization (SURY) that translates 3D urban canopy into bulk parameters. This paper presents evaluation results of the TU scheme in high-resolution simulations with a recent COSMO model version for selected European cities, namely Turin, Naples and Moscow. The key conclusion of the work is that the TU scheme in the COSMO model reasonably reproduces UHI effect and improves air temperature forecasts for all the investigated urban areas, despite each city has very different morphological characteristics. Our results highlight potential benefits of a new turbulence scheme and the representation of skin-layer temperature (for vegetation) in the model performance. Our model framework provides perspectives for enhancing urban climate modelling, although further investigations in improving model parametrizations, calibration and the use of more realistic urban canopy parameters are needed. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Garbero V.1 , Milelli M.1, 2 , Bucchignani E.3, 4 , Mercogliano P.4 , Varentsov M. 5, 6, 7, 8 , Rozinkina I.5, 6 , Rivin G.5, 6 , Blinov D.6 , Wouters H.9, 10 , Schulz J.-P.11 , Schättler U.11 , Bassani F.12 , Demuzere M.13 , Repola F.4
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  • 1 Department of Meteorology, Climate and Air Quality, Arpa Piemonte, Turin, 10139, Italy
  • 2 CIMA Foundation, Savona, 17100, Italy
  • 3 CIRA- Centro Italiano Ricerche Aerospaziali, Capua, 81043, Italy
  • 4 Regional Models and Geo-Hydrological Impacts (REMHI) Division, Fondazione Centro Euro-Mediterraneo sui Cambiamenti Climatici, Caserta, 81100, Italy
  • 5 Research Computing Center and Faculty of Geography, Lomonosov Moscow State University, Moscow, 119991, Russian Federation
  • 6 Hydrometeorologycal Research Centre of Russian Federation, Moscow, 123376, Russian Federation
  • 7 A.M. Obukhov Institute for Atmospheric Physics, Moscow, 119017, Russian Federation
  • 8 Smart Urban Nature Laboratory, RUDN University, Moscow, 117198, Russian Federation
  • 9 Environmental Modelling Unit, Flemish Institute for Technological Research, Mol, B-2400, Belgium
  • 10 Hydro-Climate Extremes Lab, Ghent University, Ghent, B-9000, Belgium
  • 11 Deutsche Wetterdienst (German Meteorological Service), Offenbach am Main, 63067, Germany
  • 12 Department of Environment, Land and Infrastructure Engineering, Politecnico di Torino, Torino, 10129, Italy
  • 13 Department of Geography, Ruhr-University Bochum, Bochum, 44801, Germany
Climate modelling; COSMO; Numerical weather; Prediction; TERRA_URB; UHI; Urban climate; Urban heat island; Urban parametrization
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