Causes of the UHI effect

Question 1

How do urban surfaces (concrete, brick and tarmac surfaces) cause the UHI effect?

Answer 1

They absorb heat from the sun during the day and slowly release the heat as long wave radiation - this is most noticeable at night, when it warms the air

Question 2

How does air pollution from cars and factories cause the UHI effect?

Answer 2

Increases cloud cover over the city. Also creates a pollution dome - a layer of pollution over the city. This traps outgoing heat radiation and reflects it back to the surface

Question 3

How does human activity cause the UHI effect?

Answer 3

Cars, factories, offices, central heating and people themselves all release heat

Question 4

How is there less evapotranspiration is urban areas?

Answer 4

Rain water is quickly removed by drainage systems, so there’s little surface water to evaporate. There isn’t much vegetation, so there’s little transpiration.

Question 5

How does less evapotranspiration caused the UHI effect?

Answer 5

Evapotranspiration uses heat energy, so less evapotranspiration means higher temperatures