monitoring urban heat island in vietnam with...
TRANSCRIPT
Monitoring Urban Heat Island in Vietnamwith Remote Sensing
Tran Thi VanHo Chi Minh City University of Technology
Vietnam National University Ho Chi Minh City
International Workshop on Air Quality in Asia, Hanoi, Vietnam June 24th‐26th, 2014
Urbanization is a main type of land use and land cover change in human history.
The population growth and socio-economic development result rapid transportation increasing, urban expansion reached to suburban areas.
A large amount of forest and agricultural land has been converted into housing, infrastructure and industrial estates.
It has a great impact on environment and climate.
Urban areas tend to experience a relatively higher temperature compared with the surrounding rural areas.
The thermal environment in urban areas is characterized by the “heat island” (HI) phenomenon also called ”urban heat island” (UHI).
Research Problems
How do Urban Heat Islands form?• Factors Communities are Focusing On
– Reduced vegetation in urban regions: Reduces the natural cooling effect from shade and evapotranspiration (increase impervious surfaces)
– Properties of urban materials: Contribute to absorption of solar energy, causing surfaces, and the air above them, to be warmer in urban areas than those in rural surroundings
• Future Factors to Consider – Urban geometry: The height and spacing of buildings affects the amount of
radiation received and emitted by urban infrastructure– Anthropogenic heat emissions: Contribute additional warmth to the air
• Additional Factors– Weather: Certain conditions, such as clear skies and calm winds, can foster
urban heat island formation – Geographic location: Proximity to large water bodies and mountainous terrain
can influence local wind patterns and urban heat island formation
UHI from remote sensing• Basis concepts
– Impervious surface (IS) as indicator for urban growth. Land use areas with large amounts of visible impervious surfaces appear hot during the day
– Thermal remote sensing –uses non‐contact instruments that sense longwave or thermal infrared radiation to estimate surface temperature
– Find out the differences between urban and rural temperature to assess the Atmospheric UHI (AUHI) and Surface UHI (SUHI)
Basis of calculation
B ‐ Black body radiation (W m‐2m‐1)T ‐ the physical (kinetic) temperature
)1(2),( )/(5
2
kThce
hcTB
Stefan-Bolzman Law for natural object
44RK TTB
KR TT 41
4
1R
KTT
TR ‐ radiation temperatureTK – kinetic (surface) temperatureε ‐ emissivity of object
Planck Equation• Define object T
• Solar radiance – main information on RS images
• Black body – complete absorption capacity of solar radiance falling on it (no reflectance, no transmistance)
• Planck equation – relationship of electromagnetic radiation and black body T
• Natural object as grey body – has own emissivity depending on its thermal status
• Stefan‐Boltzman law – relation of T and emission ability of the natural object
Electromagnetic spectrum of thermal remote sensing
Jensen 2000
Remote sensing devices detect infrared energy in regions 3‐14μm 3‐5μm : best for fire detection8‐14μm: best for heat and object temperature
UHI research in Vietnam• 2 bigest cities in Vietnam: Hanoi and Ho Chi Minh City
• Hanoi:– In 2003‐2004, the research of Le Dinh Quang on AUHI with meteorological data set in period 1955‐2000 depending on the data availabilty of each station
• Ho Chi Minh City:– 2006‐2010, the first detailed study on AUHI and SUHI with remote sensing was implemented. Next is the experimental study on PM10 as the initial step for the full evaluating the human impact on climate change in HCMC
Hanoi
‐ Location: Southern of Vietnam ‐ Total area: 2095.01 (sq. km)‐ Population: 7,521,138 (2011) (not including emigrants from other provinces)‐ Up to 2020, estimated pop. > 10 million Require houses, entertaimentfacilities, plants, machines…
Study area: Ho Chi Minh city
1. Satellite images LANDSAT (TM, EMT+) and ASTER the thermal infrared bands in 8 ‐ 12µm
Sensors Aquisited dateLANDSAT/TM 16-01-1989LANDSAT/TM 25-01-1998LANDSAT/ETM+ 13-02-2002ASTER 25-12-2006
2. Annual mean air temperature from 1989 to 2006 are collected from the Southern Region Hydrometeorological Center.
Data Set
Research UHI for HCMC1. Detect and evaluate the development of
urbanization with the key object “impervious surface” (IS)
2. Establish land surface temperature (LST) map
3. Investigate AUHI and SUHI
4. Analyze the correlation between urbanization and surface temperature change, and their impacts on environment
Urban change in HCMC in period 1989-2006
Urban land developed rapidly with variety of direction
•Spreading out from central zone
•Extending northern part zone of the city
•Particularly, along main traffic lanes in suburban areas
1989
2002 2006
1998
Urban change in HCMC in period 1989-2006
1989
1998
2002
2006
0
10000
20000
30000
40000
50000
1985 1990 1995 2000 2005 2010Năm
Diệ
n tíc
h (h
a)
Comparative results of urban area change in period 1989‐2006
This change is expressed on increasing by time with the number 6.5 times in 18 years
The line has strongest slope in 2002‐2006
YearIS
Area (ha) Rate (%)
2006 47.083,84 22,47
2002 28.576,49 13,64
1998 19.282,01 9,20
1989 7.354,22 3,51
Urban change in HCMC in period 1989-2006
1989‐1998 2002‐2006
1989‐2006
1998‐2002
Stage Years Increased (ha)
Average area increased per year (ha)
2/2002 – 12/2006 4 18.507,35 3.701,47 10%
1/1998 – 2/2002 4 9.294,48 2.323,62 6%
1/1989 – 1/1998 9 11.927,79 1.325,31 3%
1/1989 – 12/2006 18 39.729,62 2.337,04
The growth rate of urban land per year according to each stage
Urban change in HCMC in period 1989-2006
Change of temperature in period 1989-2006
> 40oC industrial zones (production activities + solar radiance)35oC ‐ 40oC resisential areas with less trees or bare land (prevalent IS)30oC – 35oC vegetated land, agricultural areas (high emissivity)< 30oC wetland, open water (high latent heat)
16‐01‐1989 25‐01‐1998
13‐02‐2002 25‐12‐2006
Surface Temperature Change in period 1989-2006
Correlation of LST and land cover
20
25
30
35
40
45
50
Khu côngnghiệp
Khu vực đôthị hóa
Nội thành Đô thị nôngthôn
Đất nôngnghiệp
Rừng Mặt nước
Nhiệt
độ
bề m
ặt (o
C)
1989 1998 2002 2006
Average LST of different land cover
LST
IS
Year Average
Temperature of whole city (oC)
IS area (ha)
16-01-1989 29,37 7.354,22
25-01-1998 31,19 19.282,01
13-02-2002 32,27 28.576,49
25-12-2006 33,34 47.083,84
• Average LST year after year tends to be higher than before, and the trend of these fluctuations are associated with trend of increasing IS area
• Relationship of LST and IS ‐strong correlationLST = 0.4 IS + 29.0R² = 0.94 29
3031323334
‐ 20,000 40,000 60,000
LST
Surface Temperature Change in period 1989-2006
1989‐1997: Ttb by year ~ 27,5oC,Tmax = 27,9oC, Tmin = 27,3oC
1997‐2006: Ttb by year ~ 28,1oC,Tmax = 28,5oC, Tmin = 27,6oC
Trend line:Tair increased ~ 0,05oC/year
Tair increased ~ 0,83oC/17 years (89‐06)
1997
y = 0.0487x + 27.343
27.0
27.2
27.4
27.6
27.8
28.0
28.2
28.4
28.6
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
Năm
Nhiệt
độ
khôn
g kh
í tru
ng b
ình
năm
T (o
C)
Annual air temperature trend in HCMC (Tan Son Hoa station)
25.0
25.5
26.0
26.5
27.0
27.5
28.0
28.5
29.0
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
Năm
Nhiệ
t độ
T (o
C)
Tan Son Hoa So Sao Xuan Loc Moc Hoa Tay Ninh Vung Tau
Tan Son Hoa
Differeneces in air temperature of stations near HCMC
Curvature of Tair at Tan Son Hoa (in urban) greater than at near other stations (in rural)
Air Temperature Change in period 1989-2006
UHI in period 1989-2006
22.0
23.0
24.0
25.0
26.0
27.0
28.0
29.0
30.0
31.0
32.0
1989
1991
1993
1995
1997
1999
2001
2003
2005
năm
T nă
m (o
C)
Ttb Tmax Tmin
22.0
23.0
24.0
25.0
26.0
27.0
28.0
29.0
30.0
31.0
32.0
1989
1991
1993
1995
1997
1999
2001
2003
2005
nămT
năm
(oC)
Ttb Tmax Tmin
Annual variation Ttb , Tmax and Tmin
Residential areas (TSH station)higher
Suburban areas (SS station)
Tan Son Hoa Station So Sao station
y = 0.0068x + 26.633
y = 0.0487x + 27.343
25.0
25.5
26.0
26.5
27.0
27.5
28.0
28.5
29.0
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
Năm
Nhiệ
t độ
khôn
g kh
í tru
ng b
ình
năm
T (o
C)
Tan Son Hoa So Sao
Annual TtbTSH: y = 0.0487x + 27.3 SS: y = 0.0068x + 26.6
UHI average intensity 1989‐2006:• max : 1.5oC năm 2003• min : 0.6oC năm 1989• mean : 1.1oC
min 0,6oC max 1,5oC
AUHI intensity in period 1989‐2006: Annual variations
24.0
24.5
25.0
25.5
26.0
26.5
27.0
27.5
28.0
28.5
29.0
29.5
30.0
I II III IV V VI VII VIII IX X XI XII
Tháng
Nhiệ
t độ
khôn
g kh
í tru
ng b
ình
(oC)
Tan Son Hoa So Sao
‐ Average monthly AUHI intensity has lowest differences in dry season, ranging from 0.7oC – 0.9oC
‐ AUHI intensity in dry season: 1.2oC – 1.8oC (from November to March)where maxima was found in January ΔT max ~ 1.8oC showed that in the dry season, the sun radiation heats up the building and surface impervious materials plus human activities made urban areas hotter than rural areas
StationMonth
I II III IV V VI VII VIII IX X XI XII
Urban - Tan Son Hoa
26,7 27,3 28,4 29,6 29,2 28,2 27,7 27,7 27,6 27,2 27,3 26,6
Rural - So Sao
25,0 25,6 27,2 28,7 28,4 27,4 27,0 26,9 26,7 26,5 26,1 24,9
ΔTTSH‐SS 1,8 1,7 1,2 0,9 0,8 0,8 0,7 0,8 0,9 0,7 1,2 1,7
1.8oC
AUHI intensity in period 1989‐2006: Monthly variations
Spatial distribution of SUHI (ha)SUHI Area in 1989 Area in 2006 Increased
times
SUHI 1 1.199 28.724 24
SUHI 2 184 4.733 26
SUHI 3 669 4.162 6
SUHI 4 - 819 8
Total 2.052 38.438 19
1 12 2
33
44
SUHI in period 1989‐2006: Spatial Distribution
• SUHI changed and expanded from the type of small areas in scattered dot forms in 1989 to type of concentrated zone in 2006.
• The magnitude of SUHI on HCMC increased nearly 19 times on 17 years
• In particular, a very large SUHI formed in the inner city was expanded in 24 times
(a) Bình Chánh-Q9 (b) Bình Chánh-Thủ Đức (c) Nhà Bè-Q12 (d) Cần Giờ-Củ Chi
(e) Nhà Bè-Củ Chi (f) Bình Chánh-Củ Chi (g) Q12-Bình Chánh (h) Q9-Bình Chánh
Intensity of SUHItb ~ 10 ‐ 15oC
SUHI in period 1989‐2006: SUHI shape in HCMC
Investigation on SUHI shape in HCMC with LST images draw several transect lines on different types of land cover from East to West and from North to South, passing through rural areas and urban areas. Results show a general picture: there is a difference of land surface temperature between urban and rural areas. This difference has an average value of about 11oC ‐ 15oC
‐ Lower Peak LST : Districts 1 & 3 ‐ commercial centre with trees differences compared to that one in Europe
‐ Highest Peak LST : urban areas Tan Binh , Go Vap (around the centre of city). These region in history had stage suffering explosion of unplanned urbanization pepople constructed houses without trees, parks, event they filled up the water bodies, which have the ecological function as the container of surface water flow
Typical UHI shape
SUHI in period 1989‐2006: SUHI shape in HCMC
Districts 1, 3
UHI and air quality• Higher temperatures of UHIs increase air conditioning energy use
• As power plants burn more fossil fuel, they increase both pollution levels and energy costs
• UHIs are not only uncomfortably hot, they are also smoggier
• Smog is created by aerial photochemical reactions of pollutants
• Reactions are more likely to occur and intensify at higher temperatures
• Higher temperatures mean, higher concentrations of smog
Experiment on detecting PM10
• Atmospheric aerosols have been implicated in the adverse effect to human health, reduce visibility, and change in energy balances
• Aerosol particles are measured as particulate matter mass for diameter less than 10 and 2.5 µm (PM10 and PM2.5, respectively) and used as a standard to evaluate air quality at the ground level
• Applications of satellite‐based observation are attractive as an additional synoptic information and visualization to ground‐based air quality data
• The research was based on Aerosol Optical Thickness (AOT) detecting from Satellite image. Optical thickness (OT) is a measure of the transmitance of a vertical column of unit cross‐sectional area. A large OT implies less atmospheric transmittance. The OT is a result of the combined effect of scattering and absorption in a vertical column. Major contributors to this extinction in the atmosphere are aerosols and air molecules. The optical due to aerosols only is called AOT.
• Using regression method, we established relations between processed image outputs (reflectance) and PM10 collected at ground stations. In‐situ PM10 was considered as dependent variable and reflectance on each band measured by LANDSAT satellite as independent variable
• Regression analysis shows the best results under the nonlinear exponential regression this regression equation is used to map spatial distribution of PM10 concentration for whole area
Experiment on detecting PM10
Dust Pollution in Ho Chi Minh City
By the Vietnamese EPA, in HCMC average total dust concentration in 1stquarter of 2010 at 6 air quality stations along the route ranged from 0.38 ‐ 0.90 mg/m3 exceeding standards from 1.3 to 3.0 times, (92% of the observed data do not meet standards).
In the 06 stations, station An Suong intersection has dust concentrations highest with overall average 0.90 mg/m3, (100% of the observations does not meet standards), there is time dust concentrations reached up 2.15 mg/m3, beyond regulation more 7 times
Natinonal Ambient Air Quality Standard(µg/m3)
Vietnam 2009
50
150
(Bob O’Keefe ‐ Health Effects Institute)
RESULTS
PM10 < 100μg/m3 found on moist areas, farmland:
. in northern Binh Chanh district border Long An
. in west district Hoc Mon border Long An
. in Nha Be, South District 9, ThanhDa peninsula and
. along the Saigon river in District 12
Areas of high PM10 concentration were found in the main traffic routes, roads, industrial areas with values higher than 200μg/m3, somewhere over 300μg/m3
in surveying where is LST higher, there is PM10 value higher
Xi măng Hà Tiên
Nga ̃ tư Thủ Đức
At intersections
Industrial areas
Plant areas
LST map PM10 map
Further Research
• Monitor problems with higher spatial resolution images for more details
• Monitor more the air quality components except PM component with remote sensing imagery supporting ground observation
• Quantity the relationship between UHI and air quality
• The outputs of research will give a usefull recommendations for planning the green and healthy city
Thank you for attention !