Temperatures: The Urban Heat Island Effect Flashcards
What is the urban heat island
A warm spot in the ‘sea’ of surrounding cooler rural air
What reasons mean that cities tend to be warmer than rural areas
- building materials
- industries, buildings and vehicles
- air pollution from industries
- any rain is disposed of quickly
How do buildings materials add to the heat of the cities
Concrete, bricks and tarmac act like bare rock surfaces, absorbing large quantities of heat during the day. This is stored and slowly released at night. (Some urban surfaces have a high reflective capacity)
How does heat from industries, buildings and vehicles add to the heat of cities
They burn fuel
Regulate temperature indoors
(Air con release hot air into the atmosphere)
How does air pollution add to the heat of cities
They increase cloud cover and creates a ‘pollution dome’, which allows in short-wave radiation but absorbs a large amount of the outgoing radiation as well as reflecting it back to the surface
How does quick disposal of precipitation add to the heat of cities
It changes the urban moisture and heat budget- reduced evapotranspiration means that more energy is available to heat the atmosphere
When is the heat island effect greatest
Under calm, high-pressure conditions, particularly with a temperature inversion in the boundary layer above the city (also better in the winter when there is a bigger impact from city heating systems)
When are urban-rural contrasts more distinct
At night when the effect of insolation is absent and surfaces that absorbed heat by day slowly release it back into the atmosphere
Are heat islands constant?
No- they vary both seasonally and diurnally
