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Urban Parameterization Review : 

Urban Parameterization Review Estatio Gutierrez

Urban Parameterization : 

Urban Parameterization The approach is to take into account the impact of horizontal (cayon floor, roof) and vertical (walls) surfaces in the momentum, heat and turbulent kinetic energy equations. Drag induced by buildings with loss of momentum (Vertical distribution) Enhancement of the transformation of mean kinetic energy into turbulent kinetic energy. Modification of the heat fluxes due to shadowing and radiation trapping effects.

Urban Representation : 

Urban Representation The city is represented as a combination of urban classes (Table approach). Every class is characterized by an array of buildings of the same width B located at the same distance from each other, but with different height.

Slide 4: 

Simplified Morphology A simplified morphology is representative of a real morphology only if the total fluxes of heat (sensible and latent), and momentum are similar to those for the real morphology The best simplified morphology should have the same values of Sroof , Swalls , Sstreet as the real morphology

Slide 5: 

Simplified Morphology 2-D 3-D

Slide 6: 

By default, the vertical resolution is 5 meters and the top of the model is located at the top of the highest building. WRF vertical levels are interpolated to get the data for each urban vertical level.

Slide 7: 

Momentum Energy Air Humidity Sink by urban surfaces Sensible heat fluxes from urban surfaces Latent heat fluxes from urban surfaces

Slide 8: 

TKE Source of TKE due to interaction between buildings and flow

Slide 9: 

Momentum: Horizontal Frictional Force Roughness length (cayon or roofs) Horizontal Surface Friction by walls

Slide 10: 

Temperature Turbulent flux of sensible heat Difference between air temp. and roof/canyon temp. Turbulent flux of sensible heat (Walls) + The surface temperature of roofs, walls and streets are computed using a heat diffusion equation at several layers in the material (Buildings’ internal temp is fixed using a table for each urban class)

Slide 11: 

TKE Shear Buoyancy The terms derived by the parameterization are interpolated from the urban vertical levels to WRF vertical levels. After all terms are calculated, the results are multiplied by the urban fraction