Model Urbanization Strategy: Summaries, Recommendations and Requirements - Meteorological and Air Quality Models for Urban Areas - page 140

15.4 Overview of Major Applications
15.4.1 Numerical Weather Prediction and Meso-Meteorological
Models
The simplest approach for meteorological models is to modify the existing non-
urban approaches (e.g., the Monin-Obukhov similarity theory, MOST) for urban
areas by introducing different values to represent each grid's effective roughness
lengths, displacement height and components and parameters of heating, includ-
ing the anthropogenic heat flux, heat storage capacity, albedo, and emissivity for
each urban land use class. Operational forecasts for urban areas using models with
increasingly more sophisticated urban schemes will require significant advance-
ments in computer power.
Beginning with Brown and Williams (1998), who included urban effects in their
turbulence closure scheme, methods with increasing levels of sophistication have
been introduced into today's mesoscale models. Masson (2000) included a detailed
canyon energy balance scheme into the surface energy balance, whereas Martilli et
al. (2002) and Dupont et al. (2004) included the effects from canyon walls, roofs,
and streets in each prognostic planetary boundary layer (PBL) equation. A similar,
but less complex urbanization scheme that shows promise toward capturing fine-
scale urban weather phenomena, was a single-layer scheme developed by Kusaka
and Kimura (2004a, b). With these advances came the requirement for detailed
urban morphological data (i.e., on the scale of a few meters), including land use
and land cover, surface roughness, building geometric and thermal characteristics,
and anthropogenic heat fluxes (Chapter 1 of this volume). Thus, depending on fit-
for-purpose analyses for specific urban applications, the next level of sophistica-
tion in NWP models may be through implementation of advanced single-layer UCP
schemes. This approach is a relatively inexpensive and practical means of improving
on the modified MOST approach.
15.4.2 Urban Air Pollution and Emergency Response Models
Urban and regional-scale atmospheric pollution models, can operate in either a
prognostic mode , or in post event analysis i.e., retrospective mode . Each mode has
priorities and requirements that do not necessarily overlap. In prognostic mode,
air quality forecasts are produced using meteorological information from NWP
forecasts. The retrospective mode is used in air quality simulations necessary to
conducting regulatory impact and cost-benefit analyses, developing source control
strategies, and performing human exposure assessments. Such simulations require
the highest precision and accuracy possible based on the most complete and highly
detailed meteorological simulations for specific meteorological scenarios of inter-
est, typically those for which air quality is poorest. For retrospective assessments,
the precision and accuracy of the meteorological simulation is more important than
timeliness.