LOCAL CLIMATE ZONES
Application to heat island studies in tropical regions
IAIN STEWART & TIM OKE
Department of Geography
University of British Columbia
Vancouver CANADA
Workshop on Urban Climatology in Tropical and Sub-Tropical Regions. The Chinese University of Hong Kong, Dec. 5-10, 2011.
LOCAL CLIMATE ZONES
Stewart I, Oke T. 2011. Submitted for publication.
LOCAL CLIMATE ZONES (LCZ)
Purpose
•
•
To improve method and consistency in urban heat island studies
To standardize the description of city and country landscapes for
urban climatologists
Approach
•
•
Divide landscapes into local-scale ‘zones’ based on surface
thermal and structural properties
Test the ‘zones’ for thermal climate differences using observational
and numerical modeling data
Application
•
Site classification, instrument siting, heat island assessment,
urban terrain and climate mapping, settlement planning, climate
modeling, weather forecasting, historical temperature analysis…
Observational support for LCZs
Summary
Departure from traverse mean (K)
•
•
•
•
Evening traverses in Vancouver, 2010
Stewart I, Oke T. 2010. Preprints, 9th Symposium on Urban Environment.
UHI datasets from
Sweden (1948, 1976),
Japan (2000-06), and
Canada (1992-2010).
Observations support the
divisional structure of the
LCZ system.
Each LCZ class has a
unique thermal climate.
Temperature patterns are
sensitive to surface relief,
surface wetness, tree
geometry, and weather.
Numerical modeling support for LCZs
Departure
fromfrom
the group
mean
DTR (K)
Departure
group
mean
DTR
-6
-5
-4
-3
-2
-1
0
1
2
3
4
(K)
5
6
7
8
9
10
Summary
S. Krayenhoff
University of British Columbia
Heavy industry
•
Co mpact highrise
•
Co mpact midrise
Open midrise
Large lo wrise
•
Open lo wrise
Sparsely built
Highly simplified approach
(trees excluded).
Urban-surface (TEB) and
plant-soil (CAPS) schemes
coupled with atmospheric
boundary layer model.
Daily temperature range
(DTR) varies with building
height & packing, land
cover, and surface wetness.
Lightweight lo wrise
•
Lo w plants
B are so il o r sand
See Krayenhoff et al., 2009. Preprints, 8th Symposium on the Urban Environment.
Natural zones more
thermally responsive than
built-up zones.
LCZs and the tropical environment
1. Source areas (wind, surface geometry, boundary layer stability)
HONG KONG
2. Zone combinations (mixed landscapes, ephemeral landscapes)
Sao Paulo, BRAZIL
Tainan, TAIWAN
LCZs and the tropical environment
3. Zone communication (datasheets)
LCZ
COMPACT HIGHRISE
LCZ 1 in Kuala Lumpur: bird’s eye view
1
DEFINITION
Form: Dense and irregular mix of tall buildings to 10s of stories. Buildings close-set, free-standing. Sky
view from street level significantly reduced. Streets paved. Buildings of steel, concrete, and glass
construction. Little or no pervious ground. High space heating/cooling demand. Heavy traffic flow.
Function: Commercial (office buildings, highrise hotels); residential (apartment towers). Location: City
core (“downtown,” central business district). Periphery (highrise subcentre, highrise sprawl).
Correspondence: UCZ1 (Oke, 2004); Dc1 and Dc8 (Ellefsen, 1990/1).
ILLUSTRATION
High angle
Eye level
LCZ 1 in Hong Kong: street view
PROPERTIES
Sky view factor
0.2 – 0.4
0
.2
.6
.4
1
.8
Canyon aspect ratio
0
>2
.2
.4
.6
.8
1
3
2
Mean building height
0
> 35 m
10
30
20
1
8
2
4
3
5
50
40
Terrain roughness class
7
6
8
Building surface fraction
40 – 60 %
0
20
40
60
80
100
0
20
40
60
80
100
0
20
40
60
80
100
0
500
1,000
1,500
2,000
0
0.1
0.2
Impervious surface fraction
40 – 60 %
Pervious surface fraction
< 10 %
Surface thermal admittance
1,100 – 1,800 J m-2 s1/2 K-1
2,500
Surface albedo
0.10 – 0.20
0.3
0.4
0.5
Anthropogenic heat flux
-2
50 – 300 W m
0
100
200
300
400
Examples of LCZ application
Nagpur, INDIA
Mapping urban
terrain
Barranquilla,
COLOMBIA
Classifying
built form
Santiago, CHILE
Assessing social
inequalities
Onitsha, NIGERIA
Quantifying UHI
magnitude
Mid-latitude city
Low latitude city
Nagpur INDIA 21°N
Mapping Urban Terrain
Purpose
•
2
1
3
To produce an LCZ map for the
city of Nagpur, and to monitor LCZ
temperatures using stationary and
mobile measurements.
4
5
LCZ 2: Compact midrise
LCZ 5: Open midrise
LCZ 9: Sparsely built
LCZ 7: Lightweight lowrise
•
To develop a spatial database of
urban form, function, and
temperature distribution, and to
propose a suitable use for that
database in local urban planning.
Investigators
•
Kotharkar R. 2011. Pers. comm.
R. Kotharkar, M. Surawar, VNIT
(Nagpur)
Barranquilla COLOMBIA 10°N
Alto Prado
LCZ 1
Compact highrise
Classifying Built Form
Purpose
•
To acquire standardized
information on built form in
Barranquilla, using the LCZ
framework.
San Roque LCZ 2
Compact midrise
Preliminary findings
•
Sud Occidente LCZ 3
Compact lowrise
Miramar
LCZ 5
Open midrise
Villadiego K. 2011. Pers. comm.
•
Eight different LCZs are
represented in Barranquilla.
Land use and land cover are
highly mixed in Barranquilla;
classification into LCZs requires
use of zone combinations.
Investigator
•
K. Villadiego, Universidad de
Paul Cézanne (Marseille)
Onitsha NIGERIA 6°N
LCZ 2: Compact midrise
Quantifying UHI Magnitude
Purpose
•
To quantify UHI magnitude through
inter-zone temperature differences
(DTLCZ).
Findings
•
LCZ 7: Lightweight lowrise
•
Largest UHI magnitudes observed in
old core (LCZ 2); smallest magnitudes
in shantytown (LCZ 7).
Impervious surface fractions of LCZs
in Onitsha are lower than midlatitude
cities; LCZ classes must be adaptable
to developing cities.
Investigator
•
Nduka IC. 2011. Research Journal of Environmental and Earth Sciences.
I.C. Nduka, Ahmadu Bello University
(Onitsha)
Santiago CHILE 33°S Assessing Social Inequalities
Purpose
•
To map LCZs in Santiago, observe
thermal differences among LCZs, and
relate these differences to socioeconomic status of district populations.
Findings
•
•
•
LCZ morphology reflects thermal and
social inequalities in Santiago.
High-density districts: high temperatures,
high heat stress, low-income populations.
Low-density districts: low temperatures,
low heat stress, affluent populations.
Investigators
•
Romero H. et al. 2010. Revista INVI .
H. Romero et al., Universidad de Chile
(Santiago)
FINAL REMARKS
What does the LCZ system offer to tropical urban climatology?
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•
•
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A simple user-friendly classification that does not require
significant resources or sophisticated technology
A flexible classification that adapts easily to hot, humid,
and dry environments
A standardized definition of UHI magnitude (DTLCZ ) that
enables valid comparisons with midlatitude cities
An educational tool for disseminating basic urban climate
information
A practical tool for linking urban design elements with
thermal climate