Environmental Engineering Reference
In-Depth Information
be created on a building-by-building basis; for modeling of an
entire metropolitan area it may still be more effective to use
remotely sensed data as discussed above.
with an enhanced version of the multi-layer UCM by Dupont,
Otte and Ching (2004) for Sacramento (California, USA) and
the potential for mitigating the UHI in response to increased
albedo of roof, walls and roads (finest model resolution 1 km)
and urban vegetation cover was investigated. It was shown that
air temperature could potentially decrease by up to 3 Cwith
a subsequent reduction in ozone concentration in most areas
of the city. The study also showed that the application of the
multilayerUCMand consideration of effects of vertical changes in
building density on the urban planetary boundary layer enabled
the atmospheric model to capture vertical variations in turbulent
kinetic energy budget components.
Regional meteorological models are an important research
tool to investigate the influence of urbanization on convection
(Shepherd, 2005). For example, using the Noah-UCM with
WRF Lin et al (2008) analyzed the impact of urbanization on
precipitation over Taipei (Taiwan). Rozoff, Cotton and Adegoke
(2003) used TEB coupled with RAMS to simulate the urban
atmosphere and its role in deep, moist convection over St.
Louis (Missouri, USA) for summer precipitation. Sensitivity
experiments show that the UHI was the most important factor
in initiating deep, moist convection downwind of the city and
that there is a large sensitivity of simulated urban-enhanced
convection to the details of the urban surface model. Shem
and Shepherd (2009) applied WRF with an urbanized roughness
approach by Liu et al . (2006) in order to investigate for a case study
the impact of urbanization on summertime thunderstorms in
Atlanta. The results show thatWRFwith the urban enhancements
captured timing and amount of convective rainfall reasonably
well and that urban characteristics in the model affected rainfall.
Several studies investigated the effects of urbanization and
accompanying LULC changes on air quality near-surface ozone
formation. For example, the Houstonmetropolitanregionwas
the focus of two air quality experiments (2000 and 2006 Texas Air
Quality Studies I and II) andmodeling efforts due to the fact of fre-
quent exeedances of the 8-hour US National Ambient Air Quality
Standard for ozone and the need to better understand the contri-
bution of regional transport and local sources to the exceedances
(Kemball-Cook et al ., 2009). Cheng and Byun (2008) and Cheng,
Kim and Byun (2008) investigated how the application of high
resolution LULC data for coupled WRF and CMAQ modeling in
the Houston-Galveston area affected simulated meteorology and
air quality. In those model simulations the Texas Forest Service
LULC dataset established with Landsat satellite imagery correctly
represented the Houston-Galveston-Brazoria area as mixtures of
urban, residential, grass, and forest LULC types thereby improv-
ing emissions, air quality and meteorological modeling. Houston
2001 LULC and lidar derived building data (650 000 buildings)
were incorporated in the NUDAPT data base (Ching et al ., 2009)
together with sets of gridded daughter products (UCM model
parameters), anthropogenic heat fluxes, and day-night popula-
tion data. Regional atmospheric modeling was carried out for
the TEXAS 2000 intensive field study using the detailed LULC
and building morphological characteristics. This improved the
accuracy of the simulation of the Galveston Bay bay-land breeze
flow reversal in the Houston area and therefore of the meteo-
rological variables (Chen, Tewari and Ching, 2007, Taha 2008a)
and ozone concentrations.
Wang et al . (2009) investigated the impacts of urban expansion
from pre-urbanization to current LULC on surface ozone for the
Pearl and Yangtze River Delta regions (China). Results show that
urbanization increases day- and night-time 2 m air temperatures,
21.4 Case studies
investigating the effects of
urbanization on weather,
climate and air quality
21.4.1 Studies investigating effects
of urban land use and land cover on
meteorology and air quality
The application of detailed remote sensing derived urban LULC
data in conjunction with UCMs and associated input parame-
ters in meteorological and air quality modeling studies for cities
around the world has strongly increased in recent years. Several
studies investigated the effects of urbanization and accompa-
nying LULC changes on various meteorological and air quality
phenomena such as precipitation, local circulations, the UHI,
and near-surface ozone formation. Other studies underline the
potential use of regional atmospheric modeling for urban air
quality regulatory and planning purposes. A very recent appli-
cation focuses on high-resolution downscaling of global climate
model output in order to investigate interactions of global climate
change and urbanization on meteorology and air quality. Here
we give an overview of some of the studies and their findings.
A series of studies showed an improvement of the quality of
the simulations for urban areas in terms of capturingmeteorolog-
ical fields and phenomena when applying single- or multi-layer
UCMs in conjunction with detailed high-resolution urban mor-
phological and LULC data instead of using the simpler roughness
approach. For example, Lemonsu and Masson (2002) simulated
the UHI circulation over Paris using the MESO-NH model with
the single-layer UCM TEB. Zhang et al . (2008) coupled the
urban canopy model of Kusaka and Kimura (2004) into Regional
Atmospheric Modeling System (RAMS) and improved the rep-
resentation of the UHI in Chongqing (China). Chen, Tewari and
Ching, (2007), Kusaka et al . (2005) and Miao et al . (2008) used
the single-layer Noah-UCM (Kusaka and Kimura, 2004) with
WRF and found that the simulation of UHI and PBL characteris-
tics was improved in Houston (USA), Tokyo (Japan) and Beijing
(China), respectively. The multilayer UCM by Dupont, Otte and
Ching (2004) was incorporated in the Mesoscale Meteorological
Model MM5 (Otte et al . 2004) and its performance evaluated for
Philadelphia (USA). The study showed that the simulated results
including the wind velocity, friction velocity, turbulent kinetic
energy, and potential temperature vertical profiles were more
consistent with the observations than that using the roughness
approach.
By applying state-of-the-art urban mesoscale meteorological
and air quality modeling as well as UCPs Taha (2008b, 2008c)
demonstrated the potential use of regional atmosphericmodeling
for urban planning (regarding UHI mitigation) and air quality
regulatory purposes. In this study MM5 was used in conjunction
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