Urban micro climates

Question 1

What is the urban heat island effect?

Answer 1

= urban areas are warmer than surrounding rural areas. Densely built up areas of the city are the warmest

• urban areas 5C warmer in summer than rural areas
• 2C warmer in winter

Question 2

What are the reasons for this effect to occur?

Answer 2

1) buildings can absorb & store heat before releasing it slowly at night
2) air pollution increases cloud cover that traps heat trying to escape
3) human activities release heat e.g. central heating and factories
4) evapotranspiration uses heat energy & is reduced in a city as water drains fast & there isn’t much vegetation
* *stronger when there’s an anticyclone as more solar radiation reaches the ground and there’s no wind.

Question 3

Why are winds in urban areas different to rural ones?

Answer 3

} friction created by tall buildings lowers average wind speed
} wind has to part to pass a building so turbulence is created
} wind coming from different directions creates vortices
} powerful gusts of wind can be channelled down long, tall streets. This is the canyon effect.