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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 8 | Copyright
Geosci. Model Dev., 11, 3427-3445, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Model description paper 24 Aug 2018

Model description paper | 24 Aug 2018

The microscale obstacle-resolving meteorological model MITRAS v2.0: model theory

Mohamed H. Salim1,a, K. Heinke Schlünzen1, David Grawe1, Marita Boettcher1, Andrea M. U. Gierisch1,b, and Björn H. Fock1,c Mohamed H. Salim et al.
  • 1Meteorological Institute, CEN, University of Hamburg, Hamburg, Germany
  • anow at: Faculty of Energy Engineering, Aswan University, Aswan, Egypt
  • bnow at: Finnish Meteorological Institute, Marine Research, Helsinki, Finland
  • cnow at: Met Office, Exeter, UK

Abstract. This paper describes the developing theory and underlying processes of the microscale obstacle-resolving model MITRAS version 2. MITRAS calculates wind, temperature, humidity, and precipitation fields, as well as transport within the obstacle layer using Reynolds averaging. It explicitly resolves obstacles, including buildings and overhanging obstacles, to consider their aerodynamic and thermodynamic effects. Buildings are represented by impermeable grid cells at the building positions so that the wind speed vanishes in these grid cells. Wall functions are used to calculate appropriate turbulent fluxes. Most exchange processes at the obstacle surfaces are considered in MITRAS, including turbulent and radiative processes, in order to obtain an accurate surface temperature. MITRAS is also able to simulate the effect of wind turbines. They are parameterized using the actuator-disk concept to account for the reduction in wind speed. The turbulence generation in the wake of a wind turbine is parameterized by adding an additional part to the turbulence mechanical production term in the turbulent kinetic energy equation. Effects of trees are considered explicitly, including the wind speed reduction, turbulence production, and dissipation due to drag forces from plant foliage elements, as well as the radiation absorption and shading. The paper provides not only documentation of the model dynamics and numerical framework but also a solid foundation for future microscale model extensions.

Publications Copernicus
Short summary
This paper gives a detailed description of the model theory of the obstacle-resolving microscale meteorological model MITRAS version 2. Detailed descriptions of the model equations and their formulations and approximations are presented. Also, detailed parameterizations of buildings, wind turbines, and vegetation in the model are introduced. Some example applications of the model are shown to demonstrate the model capacities and potential.
This paper gives a detailed description of the model theory of the obstacle-resolving microscale...