Urban Surface Energy Balance Models: Model Characteristics and Methodology for a Comparison Study - Meteorological and Air Quality Models for Urban Areas - page 89

Table 11.1 (continued)

CODE Model name Reference with details of model

TUF3D ∗ Temperature of Urban Facets in 3D Krayenhoff and Voogt (2007)

UCLM ∗ Urban Canopy Layer Model Mills (1997)

UCM Urban Canyon Model Sakakibara (1996)

UEB Urban Energy Balance Montávez et al. (2000)

UHSM Urban Heat Storage Model Bonacquisti et al. (2006)

VUCM ∗

Vegetated Urban Canopy Model Lee and Park (2008)

∗ indicates confirmed participant in comparison project.

11.2.2 Representation of the Urban Environment

There are a number of different ways to model the urban surface to predict local
scale energy balance fluxes. First, there is the issue of whether the surface con-
sists of purely built surfaces or whether vegetation is also taken into account
(Table 11.3). Generally, there are two different methods to incorporate vegeta-
tion: (1) it is treated as a separate surface (referred to here as 'tiles') that does
not interact with other surface types until the first layer of the meso-scale model
(e.g. TEB, MOSES); or (2) it is embedded into the urban area so that it affects, and
is affected by, the built environment (e.g. CLMU, SUNBEEM, LUMPS) (referred
to here as 'integrated'). Some models have both capabilities (Table 11.3). Vegeta-
tion is modelled using separate vegetation models that have been well tested, such
as in the PILPS comparisons, in extensively vegetated areas (Yang and Dickinson,
1995; Shao and Henderson-Sellers, 1996; Qu et al., 1998; Schlosser et al., 2000;
Henderson-Sellers et al., 2003; Irranejad et al., 2003) and resistance schemes that
have been developed for urban areas (e.g. Arnfield, 2000; using Grimmond and
Oke, 1991).
Second, is the issue of how the built environment is modelled. As indicated in
Sect. 11.2.1, a wide range of variables is modelled (resulting in outputs). Alterna-
tively models can be described in terms of their representation of the surface: either
slab, single layer, or multi-layer (Table 11.4). Slab models (e.g. Best, 2005) repre-
sent the urban area in terms of a surface (e.g. concrete) with appropriate thermal
characteristics. Single layer models represent a city as a layer of buildings with the
overall surface heat exchange being the sum of exchanges on individual surfaces.
This allows for more realistic representations of radiative trapping and turbulent
exchange (Masson, 2000; Kusaka et al., 2001; Harman et al., 2004a). Multi layer
models use a similar approach to single layer models, but model energy exchanges
at multiple levels within the canopy, thereby allowing for varying building heights
(e.g. BEP, TUF3D). Single and multi-layer models also differ in their spatial rep-
resentation of the urban morphology, modelling one temperature and set of energy
exchanges per facet versus multiple temperatures and energy exchanges per facet
(the latter).