By: Jay Shelton

1
Human Activity and the Urban Heat Island
Featured Articles
New Directions The growing urban heat and
pollution island effectimpact on chemistry
and climate (Crutzen 2004)
Suppression of Rain and Snow by Urban and
Industrial Air Pollution (Rosenfeld 2000)

• By Jay Shelton
• Major Atmospheric Sciences

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A Little Review
What is an urban heat island (UHI)?

• Tendency for large cities to to be warmer than
  surrounding, less metropolitan areas.

HOT!
3
Causes of the Heat Island Effect

• Increased SW absorption caused by canyon geometry
  (increased area and multiple reflection)
• Decreased LW loss caused by canyon geometry
• Increased greenhouse effect caused by air
  pollution
• Anthropogenic heat source
• Increased sensible heat storage caused by
  construction materials
• Decreased latent heat flux caused by change of
  surface type
• Decrease sensible and latent heat fluxes caused
  by canyon geometry (reduction of wind speed)

Canyons between buildings
4
The Anthropogenic Effect
Human Energy Production

• Sun supplies 235 W/m2 of energy annually.
• Human energy production (HEP)
• On average, annual HEP is .025 W/m2.
• Yes, that even includes the heat from our bodies.
• Some densely populated and highly industrialized
  areas are known to output up to 70 W/m2 of
  energy annually due to the release of high
  concentrations of air pollutants and CO2 from the
  burning of fossil fuels.

5
So whats the Issue?

• High density of pollutants from
• urban areas will affect atmospheric chemistry
  and climate.
• These effects could be
• far-reaching.

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The UHI and Weather
What effect can pollution in the UHI have on
certain meteorological events?

• Increased lightning flash frequency. (In need of
  further study)
• Changes in cloud chemistry
• Particulates acting as cloud condensation nuclei
• Inefficient coalescence
• Smaller cloud droplets
• Suppression of rain formation
• Decreased precipitation

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Normal Case
Polluted Case
.
r gt 14 µm Droplets are able to coalesce and
fall.
r lt 14 µm Droplets are unable to fall.
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Is there any Direct Evidence?

• Satellites have been monitoring ship stacks,
  mineries and factories in urban/industrial areas.
• Thick concentrations of pollutants seen in
  stratocumulus clouds.
• Pollution tracks
• Provides the first evidence that these
  particulates are changing cloud microstructure.

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Satellite Imagery
Turkey
Canada
N
N
Impact of effluents from the Hudson Bay Mining
and Smelting compound at FlinFlon in Manitoba (4).
Urban air pollution from Istanbul (1), Izmut
(2), and Bursa (3).
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Satellite Imagery
Australia
N
Pollution tracks originating from the Port
Augusta power plant (5), the Port Pirie lead
smelter (6), Adelaide port (7), and oil
refineries (8).
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Australia
7
6
1
5
2
3
4
14 µm threshold
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Why Australia?

• Numerous satellite images were taken.
• All images showed pollution tracks originating
  from pollution sources in the region.
• Cloud top temperatures were conducive to the
  precipitation formation process, but because of
  the high concentrations of aerosols, rain was not
  always able to fall.
• These results should not be surprising
• Port Augusta 520 MW Power plant operating on
  brown coal.
• Port Prairie Worlds largest lead smelter and
  refinery.
• Other sources of pollution originate from a
  cement plant and oil refineries in certain
  regions.
• What is Surprising
• Australia is probably the least (inhabited)
  polluted continent on Earth.

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Conclusions

• Satellite imagery has shown that pollution in the
  atmosphere can act as an inhibitor for
  precipitation.
• Too many particulates acting as cloud
  condensation nuclei
• Inefficient coalescense (smaller droplet sizes)
• Less rainfall
• Less precipitation in a certain area means that
  there is less available water to evaporate.
• Extra heating at the surface
• Higher temperatures
• Enhancement of the urban heat island effect
• Population is rapidly increasing
• New urban development
• Increasing output of energy/pollution

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What can be Done?
Are there any solutions or remedies that exist?

• Emission controls
• Capping policies
• Removal methods to rid pollutants from the
  atmosphere
• Smokestack scrubbers
• More plant life in cities
• Implementation of hybrid cars