Heat Island Effect and
Air Pollution
Review of last lecture
• General circulation models: Grid size. 3 usages.
Name of the basic set of equations.
• 4 components of the climate system model.
• Mesoscale models: grid size. 3 characteristics.
How do human activities change the
global climate?
Human beings are changing the global climate
system in three different ways:
• Change land cover (deforestation and
afforestation)
• Release or cleanse pollutants (aerosols)
• Release or cleanse greenhouse gases
The Heat Island Effect
Temperature distribution for Atlanta (from EPA)
Effects of vegetation
• Makes water/heat reservoir deeper (transport deep water
out of soil)
• Enhances evaporation (leafs increase evaporation area)
• Dependent on vegetation type
Vegetation feedback
Vegetation in turn is affected by environmental
conditions (e.g. seasons, droughts, global warming)
Effects of different surface types
Convective instability increases
Deeper heat reservoir (smaller T change)
Deeper water reservoir (Wetter surface)
Enhanced latent heat flux
The heat island effect
• Nighttime: City warmer than surrounding rural area
• Daytime: City has same air temperature as rural area
Temperature distribution for Atlanta
(from
Dependence of heat island effect on
population
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
• Decreased sensible and latent heat
fluxes caused by canyon geometry
(reduction of wind speed)
“Canyons” between buildings
Mitigation of heat island effect
• Greening the city
(streets and roof top)
• Change construction
materials
• Reduce anthropogenic
heat sources
Air Pollution
Video: Science to Protect the Air We
Breath (by EPA)
• http://www.youtube.com/watch?v=3PO_3e
xwN-I
Introduction
• Air pollutants are gases, liquids or solids in the air that
can adversely affect plant and/or animal life.
• Primary pollutants are pollutants that are emitted
directly by natural or anthropogenic (manmade)
processes.
• Secondary pollutants are pollutants that arise
from chemical reactions of atmospheric gases with
gases emitted by natural or anthropogenic
processes.
• There are six major pollutants: particulates, carbon
oxides, sulfur dioxides, nitrogen oxides, volatile organic
compounds, ozone
Major pollutants: (1) Particulates
• Particulates (aerosols) are solid or
liquid matter suspended in the air
(from 0.1 to 100 µm in size).
• PM10 (<10 µm) enters lungs
(associated with asthma); PM2.5
(<2.5 µm) even more dangerous
(lung cancer).
Global distribution of PM2.5 (20012006)
Image from NASA
Credit: Dalhousie
University, Aaron
van Donkelaar
U.S distribution of PM2.5 (2001-2006)
Image from NASA
Credit: Dalhousie
University, Aaron
van Donkelaar
Major pollutants: (2) Carbon monoxide
• Carbon monoxide (CO) is a colorless,
odorless gas from volcanic eruptions,
forest fires and other processes.
• Extremely toxic and dangerous to
humans and animals.
Major pollutants: (3) Sulfur dioxide
• Sulfur compounds can occur as
gaseous or aerosol forms.
• respiratory irritant. contributes to
acid fog and acid rain.
Major pollutants: (4) Nitrogen Oxides (NOX)
• Nitric oxide (NO) is a nontoxic,
colorless, and odorless gas.
• Nitrogen dioxide (NO2) is a
toxic, yellow to reddish-brown gas
that is pungent and corrosive.
Provides polluted air with the
yellow to reddish brown color.
Major pollutants: (5) Ozone
• Ozone, NO2, formaldehyde and
other gases combine with solar
radiation to form Los Angelestype photochemical smog.
• causes respiratory and heart
problems.
Major pollutants: (6) Volatile Organic
Compounds (Hydrocarbons)
• are made of carbon and
hydrogen. Examples:
methane, butane, propane,
octane, etc.
• Health effects vary
Atmospheric Conditions and Air Pollution
(1) Effect of Winds on Horizontal Transport
• High concentrations of
pollutants in a small area
(usually due to anthropogenic
sources) are the biggest air
pollution problems.
• The horizontal and vertical
transport of air pollutants by
winds help control the local
concentrations of pollutants.
• Concentrations are inversely
related to wind speed.
Atmospheric Conditions and Air Pollution
(2) Effect of Atmospheric Stability
• There are many turbulent eddies in an unstable boundary
layer, but few in a stable boundary layer
• Eddies can mix air vertically.
Unstable
Neutral
Stable
Inversions
• Inversions are absolutely stable and free of eddies
• Inversions can trap pollutants near the Earth’s surface.
Low level inversion
Upper level inversion
(most dangerous)
The smog layer in Los Angeles
Base of inversions
Global effect:
Anything released by human beings will be
transported globally by atmospheric circulations
and ocean circulations
Air Quality Index
• The EPA created an index for air pollution monitoring called
the Air Quality Index (AQI).
• A formula applies to ozone, particulates, carbon monoxide,
sulfur dioxide, and nitrogen dioxide by expressing each
pollutant on a scale that ranges from 0 to 500.
• The official AQI for any location at a particular time is the
highest of the five individual pollutant values.
Air Quality Index
History of air pollution
(1) The medieval pollution
• In medieval London, pollution from coal
burning was seen as such a serious
matter that a commission was
established in 1285 to investigate the
problem. It was reconvened three years
later with firm instructions to find a
solution.
• In 1307, during the reign of Edward I,
legislation was introduced to prevent the
use of sea coal in kilns and by
blacksmiths. It proved largely ineffective.
History of air pollution
(2) The 16th – 19th century
• Wood for burning became scarce and
expensive, and an increasing number
of domestic chimneys encouraged an
ever-wider use of fossil fuel.
• London rapidly changed from a woodburning city to one that relied on
imported coal. By the end of Elizabeth
I's reign in 1603, coal consumption in
the city had risen to more than 50,000
tons a year.
• In 1661, the diarist and protoenvironmentalist John Evelyn
published a diatribe against air
pollution in London: Fumifugium, or
The Inconvenience of the Aer and the
Smoak of London Dissipated.
Image source
History of air pollution
(3) The 20th century
• The Great Fog of 1952. Cold weather,
combined with an anticyclone and windless
conditions, trapped the pollution from
Thames-side power stations, domestic fires
and London's new fleet of 8,000 diesel
buses. The total number of fatalities was
about 12,000.
• The 1948 Donora smog. A warm air pocket
had passed high above the town, trapping
cooler air below and sealing in pollutants.
14,000 residents experienced severe
respiratory and cardiovascular problems. The
death toll was nearly 40.
• Led to several changes in practices and
regulations, including the Clean Air Act 1956.
Source
History of air pollution
(4) The 21st Century
• As China has industrialized, various
forms of pollution have increased,
which has caused widespread
environmental and health problems.
According to the World Bank in 2007,
16 of the world's 20 most polluted cities
are in China.
• Air pollution in India is a serious issue
with the major sources being fuelwood
and biomass burning, fuel adulteration,
and vehicle emission. The 2012
Environmental Performance Index
ranked India as having the poorest
relative air quality out of 132 countries.
Image Source
Summary
• Effects of vegetation: (1) makes heat/water reservoir deeper, (2)
enhance evaporation, (3) grows and dies in response to
environmental conditions
• Effects of different surface types: desert, city, grassland, forest,
sea. Deeper heat/water reservoir and enhanced convective
instability.
• Heat island effect. 7 causes
• Air pollution. 2 categories. 6 types of major pollutants (particulates,
carbon oxides, sulfur dioxides, nitrogen oxides, volatile organic
compounds, ozone)
• Effect of wind and stability on pollution: Most dangerous is upper
level inversion
• Air quality index
• History of air pollution: The Medieval pollution, The 16th-19th
centuries, The 20th century, The 21st century