Environmental Engineering Reference
In-Depth Information
Chapter 15
Model Urbanization Strategy: Summaries,
Recommendations and Requirements
Alexander Baklanov, Jason Ching, CSB Grimmond, and Alberto Martilli
15.1 Introduction
The urban canopy (UC), the layer of the atmosphere between the ground and the top
of the highest buildings, is the region where people live and human activities take
place. Because of this importance (e.g., human health, preservation of buildings)
significant efforts have been dedicated to its investigation. Such studies shed light
on the high complexity of atmospheric circulations in the UC, primarily because of
the presence of obstacles (buildings) large enough to strongly modify air flow and
the thermal exchanges between these surfaces and the atmosphere. The high level
of heterogeneity of the UC has been a challenge for atmospheric modeling in urban
areas, even for mesoscale models with a typical resolution of the order of 1 km;
the basic characteristics of the perturbations induced by the obstacles still remain-
ing unresolved at this model resolution. Over the last decade, with the increase of
computational processing power, several mesoscale modeling systems, each with
different urban canopy parameterization (UCP) schemes, have been developed and
applied with the primary aim of representing the subgrid effects of urban surfaces
on their mean variables.
15.2 “Fitness-for-Purpose” Guidance
UCP schemes used in models cover a wide spectrum ranging, from simple ones
with a limited number of parameters, such as basic roughness and scale length
for thermal or density stability, to multi-parameter sets that include vertical pro-
file descriptions of building and vegetation size and shape. As their level of detail
increases, the computational demands for running such models also increase. We
note that there are no existing rules governing the appropriate levels of detail and
specificity of UCPs that a model must have. However, it is of practical importance
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