Urban Climate Flashcards
What is the urban heat island effect
Urban areas being warmer then rural areas
What are urban heat islands
Urban areas w higher air temperatures than the surrounding rural areas eg in London
Where are the highest temperatures found
Industrial areas and the most built up eg the CBD
What are temperature sinks
There are pockets of cool air above parks and bodies of water (eg rivers or ponds)
What are temperature plateaus
Areas within the city with the same land use (eg industry) generally have the same temperature
What are temperature cliffs
Temperature can change rapidly when land use changes (eg from inner city housing to CBD, high rise buildings)
Rapid changes are referred to as temperature cliffs
6 ways in which urban climate issues can be managed
Green roofs t
Urban greening t
Cool cars t
Building design w
Laws
Public transport
How do green roofs manage urban climate
Not dark so doesn’t absorb heat
Vegetation stores water so when it transpires it takes energy out of the air
Consists of a growing medium planted over a waterproof membrane
It can reduce rainwater run off
Can increase urban biodiversity by providing habitat space for birds and small animals
How does urban greening manage urban climate
Planting trees and vegetation gives shade- surface peak temp reductions of 5-2 degrees may be possible
It can have a national cooling effect as seen by lower temp in urban parks around the world
Urban trees act as urban stores and can reduce urban flooding by intercepting rainfall and filters pollutants from the air
How do cool cars manage urban climate
Lighter coloured car shell reflects more sunlight then dark car shades
This cools the inside and reduces need for air conditioning
Cars in cities contribute significantly to higher temp and pollution levels experienced there
SO use of cool cars benefit city and driver
How do building designs- the Burj Khalifa Tower
828m tallest building in the world
Concern- windstress and wind vortexes pulling building side to side
Has to withstand gusts of over 240km/hour
Series of aerodynamics improvements had to be made to ensure building can withstand this
Soften edges of building deflect wind around the structure and prevents forming whirlpools/vortexes
The entire tower orientated relative to prevailing wind directions
Sways slowly back and forth about 2m at very top- but doesn’t suffer like skyscrapers in the past
How do laws manage urban climates
Clean air acts
Introduced smoke free zones into urban areas and this policy slowly began to clean up the air
1990- tough regulations imposed on levels of airborne pollution, particularity on PM10s
Local councils in UK now require to monitor pollution in their areas and to establish air quality management
Areas where= likely to be exceeded
London air quality standards improved
2015- NOx emissions still higher then UK and a European law recommended
Measures introduced to clean up 12% of NOx emmisions
More dust suppressants at industrial sites
How does public transport manage urban climate
ULEZ (ultra low emission zone) introduced 2020
Exhaust emission standards set and daily non compliance charge introduced to encourage cleaner vehicles to drive around London
Double decker buses operating in central London=hydbrid and all single deck- 0 emission
What are the 4 main causes of the UHI effect (these are greater in urban areas)
Absorption of heat by urban surfaces (urban- darker)
Air pollution
Heat from human activity
Less evapotranspiration
Buildings
Industry
Car friction
Rapid urban drainage
Explain how absorption of heat by urban surfaces is a cause of UHI
Concrete brick and tarmac surfaces absorb and store heat from the sun during the day
They slowly release the heat as long wave radiation
This is most noticeable at night when it warms the air
Urban surfaces also have low albedo- they absorb more energy rather then reflecting it
