funded by crti project # 02-0093rd the current meteorological models can be run at high resolutions...
TRANSCRIPT
Funded by CRTI Project # 02-0093RD
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:
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.
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 asso-ciated 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.
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
Low-density residential
Mix of nature and built
Deciduous broadleaf trees
Short grass and forbs
Long grass
Crops
Mixed wood forest
Water
Excluded
Hourly fraction profiles for vehicular traffic in the United States (Sailor and Lu, 2004)
Databases
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
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
Observations and Measurements
Dense urban district of Montreal instrumented
during MUSE
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
JD77
JD79
JD81
JD83
JD85
Short-wave radiation budget and manual albedo measurements Thermal camera imagery – JD78
Roof with snow
Roof without snow
StreetSidewalk
Modelling
- Radiative trapping and shadow effect- Heat storage- Mean wind, temperature and humidity inside the street- Water and snow on roofs and roads
- Mean urban canyon composed of 1 roof, 2 identical walls, 1 road- Isotropy of the street orientations- No crossing streets
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:
Idealized urban geometry i.e.
Representation of the principal TEB scheme variables
QH topQE top
QH trafficQE traffic
QH industryQE industry
QH roofQE roof
Water Snow
Ti bld
Troof1Troof2Troof3
Twall1Twall2Twall3
Troad1Troad2Troad3
SnowWater
QH roadQE road
Tcanyonqcanyon
QH wallQE wall
Rroof
Rwall
Rroof Snow
Rroad Rroad Snow
Rtop
Atmospheric level
Input dataPrognostic variablesDiagnostic variablesUa , Ta , qa
Meso-γ and offline
Regional NWP MUSE II
MUSETEB urban scheme
3d-turbulence
Surface fields
Anthropogenic heat sources
Modelling Databases Transfer Observations
A. Lemonsu1, S. Bélair1, J. Mailhot1, N. Benbouta2, M. Benjamin3, F. Chagnon2 , M. Jean2 , A. Leroux2 , G. Morneau3, C. Pelletier1, L. Tong4, S. Trudel2
Environment Canada; 1MSC, Meteorological Research Branch; 2MSC, Environmental Emergency Response Division; 3Quebec Region; 4MSC, Development Branch
RMetS Conference 2005Poster 940
Environment Canada
Environnement Canada
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.
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.
2-m air temperature modelled by the 1-km offline version of GEM
including TEB
299
300
301
302
303
304
07 13 19 01 07Time (Hour LST)
ObservationsModel without TEBModel with TEB
20
25
30
35
40
45
Tem
pera
ture
(oC
)
Air temperature inside the streets observed during Joint Urban 2003 and modelled by the 200-m offline version
of GEM with and without TEB
July 17th 0000LST