Urban Climate Flashcards
Describe the urban heat island effect
Urban area is significantly warmer than surrounding rural areas
Name some causes of the urban heat island
- Urban surfaces have lower albedo (absorb heat during the day and release it at night)
- less vegetation means less evapotranspiration
- glass and steel reflect heat
- power stations, vehicles and industries produce heat
How do urban forms create their own microclimates
- Surface roughness reduces windspeeds and creates turbulence
- Greater precipitation due to higher density of condensation nuclei
- Lower humidity
- More cloud coverage
What causes urban areas to experience more precipitation and by how much more
- 5 to 15% more than rural areas
- Dust and pollution from industries increase the density of condensation nuclei, essential for cloud formation
How is fog formed
More condensation nuclei means more fog is formed
Fog lasts longer in high-pressure conditions where wind is too weak to blow it away
How are thunderstorms formed
Hot, humid air rises
Cools and condenses rapidly forming cloud droplets, hail and ice (charging the storm)
Discharged as lightning
How do urban structures interfere with wind
Friction between the wind and buildings reduce urban wind velocities
What is particulate pollution
Particulates produced from power stations and vehicle emissions
Particulates combine with sulphur dioxide, from coal burning, to produce smog
What is photo-chemical pollution
Industrial and vehicle emissions react with sunlight forming secondary gases
Name some legislation policies used to reduce pollution
- Smoke free zones
- The clean air act
- Pollution targets
Name some vehicle restrictions used to reduce pollution
- Reducing the number of vehicles in urban areas via; pedestrianisation and park and ride schemes
- Congestion charge
- Selective vehicle bans
Name some technological innovations used to reduce pollution
- Catalytic converters on exhausts
- Electric and hybrid powered cars
- Pollution controls on factories, using filters
