Urbanization and Climate Change in South China · Guy Carpenter Asia-Pacific Climate Impact Centre,...
Transcript of Urbanization and Climate Change in South China · Guy Carpenter Asia-Pacific Climate Impact Centre,...
Urbanization and Climate Change in South China
Johnny ChanGuy Carpenter Asia-Pacific Climate Impact Centre
School of Energy and Environment
City University of Hong Kong
1Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Outline
Background
Effects of urbanization
Evidence
Summary
2Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Urban Area
Hong Kong
Shenzhen
Guangzhou
Farmland in Guangdong
vs. Farmland
3Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Urban or
Built-up (km2) :
Year : 1980
2230
Urban or Built-up Area in the Pearl River Delta
1980
1990
3950
1990
2000
6570
2000
4Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Effects of Urbanization on Climate
Urbanization
Emission of
atmospheric
pollutants
Changes in
land use
Heat Island
Effect/Land-
sea BreezeChanges in runoff patterns
and momentum fluxes
Changes in
cloud
condensation
nuclei
concentration
Changes in
cloud
amounts
and hence
rainfall
Changes in
radiation
budget
Changes in heat and
moisture fluxes
5Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Cloud and Rain Formation
6Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Clean vs. Polluted Clouds
7Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Heat Island Effect
8Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Land-sea Breeze Circulation
9Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Land Use Changes
1979
2003
10Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Simulated Flow in a densely built area
11Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Simulated Vertical Wind Profile
12Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Simulated Flow pattern at 5 m
13Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
evaporation
heat
exchangemomentum
exchange
LAND
ATMOSPHERE
absorption of
rain water
Land-Atmosphere Exchanges
reduced due to
increase in paved
land vs. soil
increased due
to heat island
effect
reduced due
to large
number of
buildings,
especially tall
ones
14Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
HK temperature
HK solar radiation
No. of haze
days in
Guangzhou
Climate Change
in the PRD
(related to
radiation)
15Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Climate Change
and Urbanization
in the PRD
(related to water)
PRD relative humidity
PRD rainfall
16Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Effect of increasing the roughness of the Earth’s surface on rainfall
17Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Effect of turning off the moisture flux on rainfall
18Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong
Summary
Urbanization causes substantial changes in the energy balance of the region
Such changes in energy balance will cause changes in wind flow patterns, not only within the region but also those areas downstream of the urbanized region.
A comprehensive study of the effects of urbanization on regional climate needs to be carried out to quantify such effects.
How such effects may be modified under global warming also needs to be ascertained.