The State Board for Water Pollution - The Water Act 1974 .pptx
Urban heat island
1.
2.
3.
4. The temperature of urban areas can be
significantly higher than that of the surrounding
rural areas. This fact is known as the "Urban
Heat Island" effect.
5.
6. Is this Global Warming?
• No, this is a separate phenomenon
where cities are 6-8°F warmer than
surrounding rural areas. Global warming
however could increase the impact of
urban island felt in cities in the summer
months.
7. Factors work to promote a heat island.
• Concrete and man made surfaces
• Less water in the soil and environment
• Excess energy from buildings
11. Causes
• The main cause of the UHI effect is from
the modification of land surfaces, which
use materials that effectively store short-
wave radiation.
Waste heat generated by energy
usage is a secondary contributor.
change in the energy
balance.
12. During the day in rural areas, the solar energy
absorbed near the ground evaporates water
from the vegetation and
soil(evapotranspiration). Thus, causes
evaporative cooling.
In cities, where there is less vegetation, the
buildings, streets and sidewalks absorb the
majority of solar energy input. UHIs have been
indirectly related to climate change due to their
contribution to the greenhouse effect, and
therefore, to global warming.
13. Tar, asphalt, brick and concrete absorb
insolation and release it as heat, rather than
reflecting it (without heat) like soil does.
The principal reason for the nighttime
warming is that buildings block surface heat
from radiating into the relatively cold night
sky.
14. Effects of UHI
• The extra heat from urban environments can cause
extreme weather and climatic events such as
storms, hurricanes, and floods. Warmer air can
hold more water and moisture, which results in
more precipitation. For every 1°F warming,
atmospheric water vapor increases 3-4%. Urban
heat islands can cause up to 15°F of warming, which
can increase atmospheric water vapor by more
than 50%!
17. • Every 1°C increase in air temperature,
there is a 5-10% increase in electricity
demand this energy demand need more
fossil fuels and more pollution.
Heat islands can
exacerbate the health risk of heat waves
during the summer, difficulty in
breathing in olds , heat craps, and heat
strokes.
Impact on ecosystems, the
atmosphere, and people.
18. Mitigation
1.Building green roof/wall
2.Create more city parks
3.Covers roofs and roads with light
colored materials to Increase the Albedo
4.Tree Plantation and Preservation
5. Plant Trees For Energy
Efficiency
6. Low Impact Development Techniques
19. Green roofs can be installed on a wide range of
buildings, from industrial facilities to private
residences
20. Green Roof
• A green roof, or rooftop garden, is a
vegetative layer grown on a rooftop. It
provides shade and remove heat from
the air through evapotranspiration,
reducing temperatures of the roof
surface and the surrounding air.
conventional rooftop can be up to 90°F
(50°C) warmer.
25. Mitigation
• By increasing the albedo, or solar reflectance (SR), of
surfaces such as roofs, pavements, and cars, the surfaces
absorb less solar heat and thus transmit less heat back into
the environment.
This process, called
"negative radioactive forcing," effectively cools the
environment and offsets substantial quantities of
greenhouse CO2.
26.
27. Mitigation
• Tree Strategies for Heat Island Reduction “The net
cooling effect of a young, healthy tree is equivalent
to 10 room-size air conditioners operating 20 hours
a day.” —U.S. Department of Agriculture
• “Trees properly placed around buildings can reduce
air conditioning needs by 30 percent and can save
20-50 percent in energy used for heating.” – US
Forest Service
