Environment Canada, Meteorological Service of Canada,

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