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)

Heights.

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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