Transcript Slide 1

Environnement Environment
Canada
Canada
A. Lemonsu1, S. Bélair1, J. Mailhot1, N. Benbouta2, M. Benjamin3, F. Chagnon2 ,
M. Jean2 , A. Leroux2 , G. Morneau3, C. Pelletier1, L. Tong4, S. Trudel2
RMetS Conference 2005
Poster 940
2MSC,
Environment Canada; 1MSC, Meteorological Research Branch;
Environmental Emergency Response Division; 3Quebec Region; 4MSC, Development Branch
The current meteorological models can be run at high resolutions reaching a few hundreds of meters. Since the cities cover several grid points of
the integration domain at such a scale, the impact of the urban radiative, energetic and dynamical processes must be taken into account in the
computation of surface exchanges. Thus, the Meteorological Research Branch (MRB) of the Meteorological Service of Canada launched a large
program in order to improve the representation of cities in the Canadian meteorological models including four main components:
Modelling
Databases
Transfer
Observations
TEB urban scheme
Surface fields
Meso-γ and offline
MUSE
3d-turbulence
Anthropogenic
heat sources
Regional NWP
MUSE II
Modelling
 The Town Energy Balance (TEB) (Masson, 2000) has been recently
implemented in the physics package of the Canadian meteorological
models GEM and MC2.
 Urban canopy model, dedicated to built-up covers, parameterizing
water and energy exchanges between canopy and atmosphere
 Three-dimensional geometry of the urban canopy for:
- Radiative trapping and shadow effect
Input data
Prognostic variables
Diagnostic variables
- Heat storage
U ,T ,q
Atmospheric level
- Mean wind, temperature and
humidity inside the street
R
R
R
Q
Q
- Water and snow on roofs and roads
Q
Q
Q
a
a
roof Snow
H roof
E roof
 Idealized urban geometry i.e.
- Mean urban canyon composed of
1 roof, 2 identical walls, 1 road
- Isotropy of the street orientations
- No crossing streets
Troof1
Troof2
Troof3
Rwall
QH wall
QE wall
QH traffic QH road
QE traffic QE road
Twall1
Twall2
Twall3
Observations
Model without TEB
Model with TEB
H industry
E industry
QE top
Water Snow
July 17th 0000LST
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304
top
H top
Ti bld
Extensive evaluation of the “urbanized” version of the model against
observations is currently performed within the framework of the Joint
Urban 2003 experiment (Oklahoma City, OKC, US). The first results are
encouraging giving the fact that TEB has never been tested over North
American city centers.
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Tcanyon
qcanyon
Rroad
Rroad Snow
Water
Snow
Troad1
Troad2
Troad3
Representation of the principal
TEB scheme variables
Temperature (oC)
roof
a
 For high resolution modelling application (less than 1 km), the
Reynolds time-averaged form of the compressible Navier-Stokes
equations and the generalized 3D budget TKE equation have been
introduced in MC2. This implementation will also be done in GEM soon.
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302
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301
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300
Databases
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 The implementation of a new urban parameterization requires to
provide land-use classifications including specific urban covers in
order to describe the spatial distribution and the diversity of urban
areas. A methodology based on the joint analysis of satellite imagery
(Landsat-7, Aster) and digital elevation models (SRTM-DEM, NED,
CDED1) has been developed to produce 60-m resolution urban-cover
classifications in a semi-automatic way for the main North American
cities.
60-m Montreal land-cover classification produced from the
joint analysis of Landsat-7 and SRTM-DEM minus CDED1
High buildings
Mid-high buildings
Low buildings
Very low buildings
Sparse buildings
Industrial areas
Roads and parkings
Road mix
Dense residential
Mid-density residential
07
13
19
01
Time (Hour LST)
07
Air temperature inside the streets
observed during Joint Urban 2003 and
modelled by the 200-m offline version
of GEM with and without TEB
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2-m air temperature modelled by
the 1-km offline version of GEM
including TEB
Observations and Measurements
The Montreal Urban Snow Experiment (MUSE) 2005 aimed to
document the evolution of surface characteristics and energy budgets in
a dense urban area during the winter-spring transition:
 Evolution of snow cover from ~100% to 0%
in an urban environment
 Impact of snow on surface energy and water budgets
 Quantification of anthropogenic fluxes in late winter
and spring conditions
 Evaluation of TEB in reproducing the
surface characteristics and budgets
in these conditions
Low-density residential
Mix of nature and built
Dense urban district of
Montreal instrumented
during MUSE
Deciduous broadleaf trees
Short grass and forbs
Long grass
Crops
Mixed wood forest
Water
Excluded
 The anthropogenic heat and humidity releases can be of major
importance, more specifically during wintertime. The current version of
TEB includes constant forcing of sensible and latent fluxes due to traffic
and industrial activities. A methodology is under development to
quantify in a more realistic way the anthropogenic sources associated to North American cities. Based on Sailor and Lu (2004), this
method enables the estimation of the diurnal and seasonal cycles of
releases due to metabolisms, traffic, and energy consumption.
From March 17th to April 14th, continuous measurements were conducted
to document:
- Incoming and outgoing radiation
- Turbulent fluxes by eddy-correlation
- Radiative surface temperatures
by thermal camera and infrared thermometers
- Air temperature and humidity inside street and alley
Short-wave radiation budget and
manual albedo measurements
Hourly fraction profiles for
vehicular traffic in the United
States (Sailor and Lu, 2004)
Roof with
snow
Roof
without
snow
Thermal camera imagery – JD78
During four intensive observational periods, manual measurements
complemented the database:
- Snow properties (depth, density albedo, surface temperature)
- Radiative surface temperatures on various sites and urban
elements
- Photographs of street condition
Funded by CRTI Project # 02-0093RD