7.2. Heights that need to be considered in SUEWS

A wide number of height needs to be considered before applying SUEWS. The following figure and table help to clarify the differences between these

Table 7.1 Heights important for SUEWS

Name	Symbol	Definition	Comment
Height of Forcing data for Local scale SUEWS application		Height above ground level	This should be above the RSL
Roughness SubLayer	RSL	Layer that is directly influenced by individual roughness elements	includes the UCL but is below the ISL
Urban canopy layer	UCL	Height of the roughness elements (RE)	Building, trees and other RE
Inertial sub layer or Constant flux layer	ISL	The layer where the influence of the individual RE are blended
Height above ground level	agl		height of RE, height of ISL, mid-height of building
Height above sea level	asl	Altitude of land surface	can be different between model grids (e.g. ERA5 grid and SUEWS grids)

Fig. 7.1 Critical heights that need to be considered: rural ERA5 surface-level data are “lifted” to the SUEWS forcing height \(z_a\) after altitude differences (above sea level, asl) are accounted for the forcing height needs to consider the urban canopy height (\(z_H\)) to ensure that is within the inertial sub-layer and above the roughness sub-layer (RSL). The SUEWS RSL module is used to determine the variables (air temperature \(T\), specific humidity \(q\) and wind speed \(U\)) at the height desired within the RSL for an application. Figure not to scale.

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