Environmental Engineering Reference
In-Depth Information
Table 15.1 Ranking of importance of variables by (example) application
Application
versus
importance
Urban
climatology
Emergency
response
Weather
forecasting
Air quality
Urban planning
Wind speed
Very
important
Important
Very
important
Important above
the canopy
Very important
Wind
direction
Ve r y
important
Important
Very
important
Important above
the canopy
Very important
Temperature
(and
Humidity)
Important
Very, very
important
Important
Very important
(2-m
temperature)
Very important
Pollutant con-
centration
Ve r y, ve r y
important
Ve r y
important
Very important
Turbulent
Fluxes
Ve r y
important
Ve r y
important
Very important
(at the top of
the canopy)
Very important
of heat exchange between surfaces (walls, roofs, and streets) and the atmosphere,
thus impacting urban microclimates.
Additional criteria are needed for a robust evaluation based on fitness of purpose
concepts. For example, whereas predicted pollutant concentration is a crucial vari-
able for air quality studies, it will be important, in some applications, to focus on
different statistical measures. For example, when considering averaging time, one
should be clear whether the focus is on the averaging period, on the peak or the
number of hours above a certain threshold, or on some other discriminator. Simi-
larly, it would be useful to set objectives based on the degree of precision needed
(e.g., Is it sufficient to have a modeled wind speed within 1 m s 1 of measurements
for air quality simulations?). Thus, practical targets to be reached in terms of level
of precision of outputs for the UCP implemented into models would be established
for the models' intended use at the outset of the evaluation.
15.3 Strategy to Urbanize Different Types of Models
Current types of UC schemes available for model implementation are reviewed in
this section, in the context of their application requirements. Given different mod-
eling objectives, there are several types of UC schemes and associated atmospheric
models available. They can be separated into three primary categories:
(1) single-layer and slab/bulk-type UC schemes,
(2) multilayer UC schemes, and
(3) obstacle-resolved microscale models.
The first two categories are sufficiently simple (in their grid-averaged rep-
resentation of urban morphological features as parameters) to be coupled into
classical numerical atmospheric models. The third corresponds to computational
fluid dynamic (CFD)-type explicit building-scale resolved models.
 
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