Question 04
Study Figure 2 which shows temperatures in Dublin at 2200 hours on a November
evening. Describe and comment on the extent of the urban heat island shown. 7 marks
Mark scheme.
Level 1: simple statements of features from the figure such as areas of high or low
temperatures with no commentary on any aspect. Good description only = Max L1 1-4
Level 2: commentary on the nature of the heat island. Some sophistication of description,
and evidence of geographical thinking. 5-7
Candidate A
The urban heat island shown displays a clear difference in temperature between the urban
area of Dublin and the surrounding area with maximum temperatures of 3.5C in the north of
the urban area and minimum temperatures of -1.5C on the outskirts and surrounding areas
of the city. There is a steep decrease of 2.0C to -1.5C along the north and north-western
edge of the urban area suggesting that there is a somewhat sharp contrast between urban
setting and countryside. This steep decrease occurs because of the difference in materials
between urban area and countryside. Those used in a city such as Dublin include concrete,
tarmac, brick and glass which have different physical properties to the natural grass, soil and
plants of the countryside. Urban materials absorb heat in the day (although little insolation
here due the low angle of the sun) and release it slowly at night meaning that night time
temperatures are higher than those of the surrounding areas. A sharp contrast in materials
ie concrete to soil would result in a decrease in temperature as shown here. Where the
isotherms are further apart in the south west showing a gradual decrease in temperature
implies a more gradual transition between the urban area and countryside perhaps an area
of suburbs. Where the river Liffey opens in the Irish Sea isotherms are fairly close together
reflecting the cooling effect of the water but also how the heat lost from the urban area has
also affected the inlet of water as I would expect it to be a much lower temperature on a
November evening in winter.
The urban eat island as shown by the isotherms is not a perfect circle nor does it perfectly
correspond to the shape of the urban area. This is due to the distribution of urban
structures and concentration of traffic where temperatures are highest (3.5C) is most likely
the location where traffic is most concentrated as emissions from vehicles heat up the
atmosphere as do central heating systems in buildings. The protrusion of the urban area just
north of the river Liffey in A3 and corresponding isotherms is most likely due to a housing
development on the outskirts of the city centre. Where isotherms are widely spaced suggest
less densely populated or built-on areas, housing schemes and suburban areas. (7)
Question 05
Explain how urban structures and layout affect winds. 8 marks
Mark scheme.
Level 1: simple statements of how buildings influence air flows such as acting as windbreaks,
creating turbulence and causing a ‘canyon’ effect. 1-4
Level 2: detailed relationships between buildings and air flow, such as the importance of the
separation of buildings, and the complexity of flow around a building/buildings. 5-8
Candidate A
Urban structures and layout affect winds in that friction from urban structures and tall
buildings cause winds to lose energy and to be diverted (respectively) ultimately leading in
calm conditions and light winds. When moving through an urban area winds must pass
through areas of skyscrapers, oddly shaped buildings and brick built structures. Energy is
lost when the movement of air encounters friction and hinders its ability to move as fast.
Friction van be small scale such as rough surface of brick buildings or large scale such as
large tall structures which wind must go around. This results in a reduction of wind speeds
in urban areas. Also the more densely built up an area is the less wind has an effect as the
air must be diverted around many structures and can in fact be diverted round the area
altogether. In terms of layout, parallel built streets, especially long narrow streets with
buildings either side can cause wind to be funnelled down these passages creating ‘wind
tunnels’ where wind speeds increase greatly, this increases the average wind speed of an
urban area. The same effect occurs with narrow passages/gaps between tall buildings, wind
is forced through in a wind tunnel creating high speed winds. In urban areas with a less
structured layout eg wide streets with building s of moderate height set out in an unparallel
layout, wind is less affected whilst speed is still reduced by friction, the occurrence of wind
tunnels is less as the conditions are not conducive to such an event. (5)
Question 06
With reference to examples, discuss how pollution reduction policies have attempted to
lessen the incidence of particulate pollution and photochemical smog. 10 marks
Mark scheme.
Level 1: simple statements of pollution reduction policies which could apply to any area of
the world, and to any form of atmospheric pollution. No specific detail provided. 1-4
Level 2: specific statements of pollution reduction policies which can be clearly attributed to
named areas and/or forms of pollution access this level. 5-8
Level 3: a fully developed answer, with good elaboration and discussion of a variety of
pollution reduction policies each clearly attributed and being different from each other. 9-10
Candidate B
In modern times particulate pollution and photochemical smog have become serious
problems. The presence of dust in urban areas is 1000% that in rural areas. Photochemical
smog is made when sunlight hits both oxides of nitrogen and hydrocarbons. A vague yellowy
fog is created reducing visibility leading to road accidents and being a health hazard, some
stipulating it to be a cause of asthma and other breathing problems. The Greek city of
Athens is famous for its photochemical smog.
There are many different pollution reduction policies that can be put into place. For
example legislature and legal policies can be enforced such as the Clean Air Act of 1956 of
Britain. This act banned any form of untreated coal to be allowed to be burnt. Soot used to
be a main particulate pollutant in 1950s Britain and smog a mixture of smoke and fog was
common. By introducing the Clean Air Act within a matter of years smog was no longer a
problem and the air was measured to be of better quality.
Another example would be traffic calming schemes and traffic reduction schemes, their
aims to reduce the amount of vehicles on the road producing particulate pollutants and
oxides of nitrogen. The congestion charge in London is a set fee which people must pay in
order to enter the built-up capital city. Since the charge was introduced traffic has
decreased enormously in London and the number of vehicles on its roads has fallen. Now
put off by the expensive congestion charge many previous motorists prefer to walk through
the city.
Public transport systems have also been used to reduce such particulate pollution. The more
people sharing public transport means less cars will be emitting particulate pollution. By
upgrading the transport system or providing incentives such as cheap fares more people
would be encouraged to use public transport. This has been shown to work in Doncaster
where there has been many improvements in the bus service. A new airport like bus depot
is kept clean and stylish and a bus corridor from Doncaster town centre to Rossington gives
buses priority at traffic lights and smooth bus only lane journeys which can be quicker than
driving.
Many of these schemes and policies have been put into action around the world and have
ensured that particulate pollution and photochemical smog have been reduced severely.
(9)