San%20Antonio%20

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San Antonio Hot Islands
Sandra Ytuarte December 1, 2004
Noreen Castellano
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What is a Hot Island?

• On warm summer days the air in urban areas can be
  6-8F hotter than the surrounding areas.
• In the downtown areas of cities, buildings and
  pavements made of dark materials absorb the suns
  rays instead of reflecting then away.
• These higher temperatures contribute to the
  summer warming trends that occur in these urban
  areas.

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What causes a Hot Island?

• Buildings, Concrete Asphalt in the downtown
  areas made of dark materials.
• The lack of vegetation in city which does not
  provide shade for the buildings or allow for the
  air to be cool.

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What problems are caused by Hot Islands?

• Higher temperatures in the city lead to an
  increase in air conditioning use, which makes the
  downtown area more expensive to maintain.
• Higher temperatures also raise pollution levels
  in the downtown areas which is a health concern.

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Factors Contributing to Hot Islands

• Dark roofing materials which absorb more heat
  from the sun.
• Pavements made of black asphalt concrete absorb
  the energy from the sunlight and convert it into
  thermal energy the pavements get hotter.
• Lack of vegetation which does not allow for
  shading and cool ambient air.

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Roofing Materials

• The solar reflectance index (SRI) is a measure of
  how hot materials are in the sun
• A traditional roofing material has an SRI between
  5 (brown shingles) and 20 (green shingles)

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Roofing Materials

• In the past white shingles were very popular due
  to their high SRI of 35.
• Unfortunately they lost popularity due to them
  getting dirty easily.
• Currently light colored roofing materials are
  preferred.
• They increase the solar reflectivity of a
  building and lower its temperature.

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Roofing Materials
Black Shingle Conventional White Shingle AdvancedWhite Shingle


Reflectance 5Temperature 180F Reflectance 29Temperature 157F Reflectance 60Temperature 128F
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Solar Reflectivity of Roofing Materials
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Pavements Reflectivity

• Albedo or reflectivity is the ratio of the amount
  of light reflected from a material to the amount
  of light shined on the material.
• For pavements the sunlight is converted into
  thermal energy and the pavement gets hotter.

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Pavements Reflectivity

• A lower albedo would suggest that more light is
  absorbed by the pavement and the pavement is
  hotter.
• A higher albedo would suggest that less energy is
  absorbed and the pavement is cooler.
• The reduction in the temperature of the pavement
  would also reduce the heat island effect.

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Albedos of Pavements

• Dark fresh Asphalt
• Albedo0.05, with a temperature of 123F
• Aged Asphalt
• Albedo 0.15, with a temperature of 115F
• Asphalt with a coating
• Albedo 0.51, with a temperature of 88F

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Albedos of Pavements
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Albedo of Pavement
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Vegetation in the City

• The lack of vegetation in a city does not allow
  trees, shrubs, and other plants to shade the
  buildings pavements.
• When vegetation is present the plants and trees
  intercept solar radiation and cool the air.
• This is called Evapotranspiration.

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Evapotranspiration

• Evapotranspiration occurs when plants secrete or
  transpire water through pores in their leaves
  this is similar to how people sweat.
• This water draws heat as it evaporates, cooling
  the air in the process.

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Vegetation in the City

• A single mature, properly watered tree with a
  crown of 30 feet can evapotranspire up to 40
  gallons of water in a day.
• This is the benefit of having a downtown area
  full of vegetation.

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Evapotranspiration
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Vegetation in the City
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Vegetation in the City
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Factors that would reduce Hot Islands

• Light roofing materials made of white shingles
  with a high reflectance.
• Pavements in the downtown area with a high
  albedo.
• The presence of plants and trees in the city
  which cool the air by Evapotranspiration.

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Factors that would reduceHot Islands

• Cool roofs pavements can reflect the solar
  radiation, and reduce the heat being created.
• Vegetation in the cities would reduce the
  ambient temperature through evaportranspiration.
  
• Mitigation strategies of planting trees and
  shrubs, installing reflective materials for roofs
  and pavements in the urban areas.
• Evaluate the mitigation strategies in a year,
  record and evaluate the data to see if there has
  been any change in temperature for the urban
  areas.

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San AntonioHot Islands

• Each citys urban heat island varies based on the
  city structure and thus the range of temperatures
  within the island vary as well.
• In our stone-like cities, they only slowly loose
  heat at night, thus causing the greatest
  temperature differences between the city and
  country side to take place at night.

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San AntonioHot Islands

• In this project the temperatures in the downtown
  San Antonio area were recorded during the day and
  evening for the month of July 2004.

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Data Acquisition

• NASA Earth Observing System Data Gateway.
• The data will be ordered through Land Processes
  DAAC (LP DAAC) User Services from the U.S.
  Geological Survey.
• July 1, 2004 through August 1, 2004, and time
  range - 200 p.m. MODIS/Aqua (MOD 11 EOS PM) was
  used to capture data
• Day afternoon (2pm)
• Night
• This information is then downloaded and the MODIS
  Tool MRT is used the transfer the HDF files to
  tif files.
• These tif files are then projected to UTM14 and
  then ENVI software is used to cut sub sets and
  stack 30 images into one image file.
• Envi software was used to produce images to show
  these temperature ranges of the San Antonio Area.
  
• Excel software was used to graph the temperatures
  for Day and Night temperature ranges.

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Temperature Data Conversions

• The results were taken from the density slice
  range screen from Envi

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Temperature Data Conversions

• The temperatures were converted to F by the
  following formula.
• Convert from K to C
• Value (DN) x 0.02 K
• K 273 C
• Convert from C to F
• Value C x 1.8 32 F

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3-Dimensional San Antonio Area
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July 13th Night Temperature Ranges
The hottest area for this day ranges from
81.07F - 84.20F. This is shaded in the color
Cyan which is in the Southeast portion of San
Antonio. The other temperature ranges are the
following 32.00F- 66.06 F in the color Black,
66.09F-67.93F in the color Yellow , 67.96F-
69.80 F in the color Maroon , 69.84F- 71.67 F
in the color Sea Green , 71.71F- 73.54F in the
color Red, 73.58 F- 75.42F in the color Green,
75.45F - 77.29F in the color Brown , 77.32F -
79.16F in the color Blue, and 79.20F- 81.03F
in the color Orchid
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July 14th Night Temperature Ranges
The hottest area for this day ranges from 73.58
F- 75.42F. This is shaded in the LimeGreen
color which is in Southeast the portion of San
Antonio. The other temperature ranges are the
following 32.00F- 66.06F in the color Black,
66.09F - 67.93F in the color Yellow, 67.96F-
69.80Fin the color Maroon, 69.84 F- 71.67 F in
the color Sea Green, and 71.71 F- 73.54F in
the color Red.
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July 15th Night Temperature Ranges
The hottest area for this day ranges from 81.07F
- 84.20F. This is shaded in the color Cyan which
is in the Southeast portion of San Antonio. The
other temperature ranges are the following
32.00F- 66.06 F in the color Black,
66.09F-67.93F in the color Yellow , 67.96F-
69.80 F in the color Maroon , 69.84F- 71.67 F
in the color Sea Green , 71.71F- 73.54F in the
color Red, 73.58 F- 75.42F in the color Green,
75.45F - 77.29F in the color Brown , 77.32F -
79.16F in the color Blue, and 79.20F- 81.03F
in the color Orchid
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July 16th Night Temperature Ranges
The hottest area for this day ranges from 73.58
F- 75.42F. This is shaded in the Lime Green
color which is in the Downtown Center and some in
the Southeast the portion of San Antonio. The
other temperature ranges are the following
32.00F- 66.06F in the color Black, 66.09F -
67.93F in the color Yellow, 67.96F- 69.80Fin
the color Maroon, 69.84 F- 71.67 F in the color
Sea Green, and 71.71 F- 73.54F in the color
Red.
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July 19th Night Temperature Ranges
The hottest area for this day ranges from 81.07F
-84.20F. This is shaded in the color Cyan which
is in the Southeast portion of San Antonio. The
other temperature ranges are the following
32.00F- 66.06 F in the color Black,
66.09F-67.93F in the color Yellow , 67.96F-
69.80 F in the color Maroon , 69.84F- 71.67 F
in the color Sea Green , 71.71F- 73.54F in the
color Red, 73.58 F- 75.42F in the color Green,
75.45F - 77.29F in the color Brown , 77.32F -
79.16F in the color Blue, and 79.20F- 81.03F
in the color Orchid.
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July 20th Night Temperature Ranges
The hottest area for this day ranges from 81.07F
- 84.20F. This is shaded in the color Cyan which
is in the Southeast portion of San Antonio. The
other temperature ranges are the following
32.00F- 66.06 F in the color Black,
66.09F-67.93F in the color Yellow , 67.96F-
69.80 F in the color Maroon , 69.84F- 71.67 F
in the color Sea Green , 71.71F- 73.54F in the
color Red, 73.58 F- 75.42F in the color Green,
75.45F - 77.29F in the color Brown , 77.32F -
79.16F in the color Blue, and 79.20F- 81.03F
in the color Orchid.
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July 24th Night Temperature Ranges
The hottest area for this day ranges from 84.24F
- 86.11F. This is shaded in the color Coral
which is in the Southeast portion of San Antonio.
The other temperature ranges are the following
32.00F- 66.06 F in the color Black,
66.09F-67.93F in the color Yellow , 67.96F-
69.80 F in the color Maroon , 69.84F- 71.67 F
in the color Sea Green , 71.71F- 73.54F in the
color Red, 73.58 F- 75.42F in the color Green,
75.45F - 77.29F in the color Brown , 77.32F -
79.16F in the color Blue, 79.20F- 81.03F in
the color Orchid, and 81.07F - 84.20F Cyan.
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July 27th Night Temperature Ranges
The hottest area for this day ranges from77.32F
- 79.16F. This is shaded in the color Blue which
is in Southeast the portion Southeast portion of
San Antonio. The other temperature ranges are the
following 32.00F- 66.06F in the color Black,
66.09F - 67.93F in the color Yellow, 67.96F-
69.80Fin the color Maroon, 69.84 F- 71.67 F in
the color Sea Green, 71.71 F- 73.54F in the
color Red, and 73.58 F- 75.42F Green.
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July 31st Night Temperature Ranges
The hottest area for this day ranges from
79.20F- 81.03F. This is shaded in the color
Cyan which is in the Southeast portion of San
Antonio. The other temperature ranges are the
following 32.00F- 66.06 F in the color Black,
66.09F-67.93F in the color Yellow , 67.96F-
69.80 F in the color Maroon , 69.84F- 71.67 F
in the color Sea Green , 71.71F- 73.54F in the
color Red, 73.58 F- 5.42F in the color Green,
75.45F - 77.29F in the color Brown , and
77.32F - 79.16F in the color Blue.
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July 4th Day Temperature Ranges
The hottest area for this day ranges from 96.76
F - 98.60 F. This is shaded in the orchid color
which is the Northeast part of San Antonio. The
other temperature ranges are the following
94.89F - 96.73F in the blue color, 93.02 F -
94.86F in the sienna/brown color, 91.15F-
92.98F in the green color, and 89.28F - 91.11.
F in the red color.
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July 5th Day Temperature Ranges
The hottest area for this day ranges
from106.05F-109.36F. This is shaded in the
Orange color which is the Northwest central
portion of San Antonio. The other temperature
ranges are the following 0.00F - 89.60F in the
Black color , 99.36F-94.96F in the Thistle
color , 95.00F -102.16F in the Maroon color,
95.00F-100.04F in the Green, 98.64F-02.16F in
the Purple color , 100.08 F- 104.11F in the
Cyan color, 102.24F -106.02F in the Yellow
color, 104.14F -107.92F in the Red color, ,
107.96F -116.56F Blue color.
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July 13th Day Temperature Ranges
The hottest area for this day ranges from
116.64F 120.20F. This is shaded in the Purple
color which is in the Center of Downtown San
Antonio. The other temperature ranges are the
following 32.00F-84.20F in the color Black,
91.44F -95.00F in the color Brown, 95.04F -
98.60F in the color Blue , 98.64F - 102.20F in
the color Orchid, 102.24F -105.80F in the color
Sea Green , 105.84F -109.40F in the color
Orange, 109.44F-113.00F in the color Hot Pink,
and 113.04F-116.60F in the color Yellow.
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3 Dimensional of July 13th
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July 18th Day Temperature Ranges
The hottest area for this day ranges from116.64F
-119.30F. This is shaded in the Yellow color
which is in the Upper Northern part of San
Antonio. The other temperature ranges are the
following 32.00F-87.80F in the color Black,
87.84F-98.60F in the color Blue,
98.64F-102.20F in the color Orchid,
102.24F-105.80F in the color Cyan,
105.84F-109.40F in the color Orange , 109.44F-
113.00F in the color Green, 113.04F -14.91F in
the color Red, and 114.94F -116.60F in the
color Brown.
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Night Average Temperature Results
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Day Average Temperature Results