1. Microclimates

2. Objectives
Understand how urban areas have distinct
climates
Understand how forests and water have distinct
climates

3. Microclimatology is the study of climate over a
small area
It includes both changes resulting from
construction and natural features

4. Urban climates
More dust and condensation
Create heat
Alter chemical composition and moisture
content of air
Albedo
Air flow

7. Urban Heat Island
Most building materials non-reflective
Dark coloured roofs, concrete/brick walls, tarmac
roads – high thermal capacity
Further heat – car fumes, factories, power
stations, central heating and people

8. Effects
Daytime temp average 0.6 C +
Night-time temperatures 3-4 higher
Dust & cloud blanket, buildings as radiators
Mean winter temperature 1-2 C + rural areas
(Rural areas even colder with snow cover)
Mean summer temperature 5 C +
Mean annual temperature is higher by Chicago
0.6 C -London 1.3 C

9. Less Sunlight
High buildings
More cloud and dust
Winter can be up to 50% less

10. Wind
Buildings act as wind breaks
Building act as 'canyons'
Local thermals
Smoke and smog

11. Relative Humidity
6% lower due to lack of vegetation and lack of
water surfaces

12. Cloud
10% more frequent cloud cover
Due to convection currents
5-15% more rain
Strong thermals increase thunder
Fog greater

13. Atmospheric Composition
7 times more dust
Gaseous and solid impurities
200 times more sulfur dioxide & 10 times more
nitrogen
Smog

14. Forests
Incoming radiation absorbed and trapped
Small diurnal range
RH higher during summer esp. in deciduous
forests
Heavy rain can be caused by increase
evapotranspiration (Rain Forests)
Windbreaks

15. Water Surface
Less insolation absorbed due to albedo
Small dinurnal range – like the UK
High RH esp. in summer
More rain or fog
Strong winds

16. Objectives
Understand how urban areas have distinct
climates
Understand how forests and water have distinct
climates