environment canada, meteorological service of canada, s. bélair, a. lemonsu, l. tong, j. mailhot...
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Environment Canada, Environment Canada, Meteorological Service of Canada, Meteorological Service of Canada,
S. BS. Bélair, A. Lemonsu, L. Tong, élair, A. Lemonsu, L. Tong,
J. MailhotJ. Mailhot
CRTI Project # 02-0093RD
Joint Urban 2003 ExperimentsJoint Urban 2003 Experiments
GEM-LAM 2.5 km
GEM-LAM 1 km
GEM-LAM 250 m
OKC
Incoming flow
15-kmRegional model
IC + LBC
IC + LBC
IC + LBC
TEB is used in 2.5 km, 1 km, and 250-m models
IOP6 (Daytime): Urban Heat IslandIOP6 (Daytime): Urban Heat Island(1-km Results)(1-km Results)
Rural Stations
Heat Island Index
ObsUrbanCrops
In red,
PWIDS stations used for model verification
City Center Stations
TEB does not make much differences over rural areas (expected!)
Significant improvement in the city (cooler in the day, warmer in the night)
IOP6 (Daytime): Well-Mixed LayerIOP6 (Daytime): Well-Mixed Layer(1-km Results)(1-km Results)
Not enough vertical resolution to capture the sharp inversion at the top of the well-mixed layer
Model soundings are not sensitive to the inclusion of TEB. Hypothesis is that horizontal variability comes from meteorology
IOP9 (Night): Urban Heat Island IOP9 (Night): Urban Heat Island
OKC
50-m Air Temperature
(valid at 0500 UTC)
Warm plume from the city
IOP9 (Night): Shallow Quasi-Neutral Layer IOP9 (Night): Shallow Quasi-Neutral Layer
ANL (downwind)
PNNL (upwind)
OBS
MODEL
OBS
MODEL
OBS
MODEL
Norman(rural)
Urban soundings Neutral nocturnal layer is well captured by the model. But too warm (not due to city treatment, see sounding at Norman)
IOP9 (Night): Daytime turbulence IOP9 (Night): Daytime turbulence
OKC
1000-m Vertical Motion
(valid at 2100 UTC)
Flow is quasi-laminar in the first portion of the domain (why we use a rectangular domain oriented along the low-level winds)
Montreal Urban Snow Experiments (MUSEs)Montreal Urban Snow Experiments (MUSEs)
• 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 the surface energy and water budgets
– Quantify anthropogenic heat fluxes in late winter and spring conditions
• Evaluate the Town Energy Balance model (TEB) in reproducing the surface characteristics and budgets in these conditions
• Gain expertise in urban measurements
OBJECTIVES
Residential location:- Horizontally homogeneous- two and three-storey attached buildings- Away from tall buildings and trees,
rivers, mountains, parks
1 km1 km
MUSE-2005: 17 March to 14 April 2005
MUSE-2006: 10 February to 31 March 2006
Measurements During MUSE-2005Measurements During MUSE-2005
ALLEYFABRE
STREET
Bac
kyar
d
Bac
kyar
d
Fro
ntya
rdS
idew
alk
Snow Snow
TRAILER
Tair Qair Twall
Tair Qair Twall
Infrared cameraNet radiometer
3D sonic anemometerH2O/CO2 analyzer
Fine wire thermocoupleAnemometer Temperature
Humidity
IOP: 26-h observing periods with manual measurements
AlbedoSnow depthSnow densitySurfaces temperaturePhotographs
Fro
ntya
rd
Sid
ewal
k
Snow depth
20 m
TemperatureHumidity
4 m
Fine wire thermocouple
7 m
Manual measurements were also taken on perpendicular street during IOP
In blue: continuous measurements
An Interesting First Week of MeasurementsAn Interesting First Week of Measurements
-200
0
200
400
600
800
1000
Rad
iativ
e flu
x (W
/m²)
0,00
0,05
0,10
0,15
0,20
0,25
0,30
Alb
edo
Solar incident Solar reflected Daily average albedo
-100
0
100
200
300
400
Tur
bule
nt fl
uxes
(W
/m²)
0
1
2
3
4
5
6
7
8
Bow
en r
atio
Sensible heat Latent heat Average Bowen Ratio
Solar Radiation Turbulent Fluxes
As snow melts, there is a rapid decrease of albedo…
… associated with an increase of the Bowen Ratio
Footprint AnalysisFootprint Analysis
0.0
0.1
0.2
0.3
0.4
Fra
ctio
n (-
)
0.0
0.1
0.2
0.3
0.4
Fra
ctio
n (-
)
Ve
ge
tatio
n
Pa
rks
Ba
ckya
rds
Bo
rde
rs
Sid
ew
alk
s
Ro
ad
s
Alle
ys
Bu
ildin
gs
Bld
are
as
Bld
po
lyg
on
s
Westerly
Easterly
Similar distributions of surface types over the westerly and easterly footprints. But other factors may influence the turbulent measurements (e.g., installation of instruments on the tower, which is optimal for southwesterly winds).
Energy Budget AnalysisEnergy Budget Analysis
With snow No snow
RN
Residue
H
LE
RN
Residue
H
LE
S
S L
L
S
S L
L
Residue = Storage + snow melt – Anthropogenic heat fluxes