Inclusion of a multi-layer drag approach in urban surface schemes: which benefits ?
Valéry Masson, CNRM/Meteo France, Toulouse, France; and R. Hamdi and G. Pigeon
The intercomparison exercice allows to analyse the impacts of the main differences between the physics in the models (e.g. chosen geometry, heat transfer equations, canopy air discretization, building discretization, radiation and turbulent exchanges...). However, this can sometimes be difficult due to the fact that several physical formulations are different between models, not allowing to separate clearly the role of each parameterization choice.
Here is presented an improvement of the TEB scheme, with a multi-layer approach for the in and above canopy air. This is a major change in the type of model (from single layer to multilayer), while keeping the same other approximations. The formulation to include air prognostic layers in the surface scheme is derived from the atmospheric equations. New variables are wind, temperature, humidity and Turbulent Kinetic Energy. In TEB, drag forces are added, the heat fluxes by buildings interacts on each of the layers intersecting those, and they modify the Tke equation. The impact of the atmospheric layers is then presented, using the intercomparison exercice data (for which the two versions of TEB were used).
The proposed method of inclusion prognostic atmospheric layer inside TEB (or other surface scheme) allows a finer vertical resolution of the atmosphere (down to the road surface), while keeping a simple way to couple the surface scheme with and the numerical efficiency of the atmospheric models above.
Session 3, Weather Forecasting for Urban Areas
Wednesday, 14 January 2009, 8:30 AM-10:00 AM, Room 124B
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