1. Urban Microclimates
I can define and apply the concept of an urban heat island
I can identify reasons for an issues stemming from urban air pollution
I can identify other issues of urban microclimates such as annual rainfall and wind gusts. 1

2. Urban Heat Island An effect in large cities that causes the city to be
warmer then the
surrounding
countryside 2

3. This causes the UHI to be most evident at night
Causes of UHI
1 Materials: Dark roofs and asphalt absorb heat during the day and slowly release it at night.
This causes the UHI to be most evident at night 3

4. Causes of UHI
2. People: Factories, buildings and people in general give off heat. The more buildings and people, the more heat given off. 4

5. Causes of UHI
3. Lack of evaporation: Evaporation causes cooling. In an area with few plants and lots of non-porous surfaces.
Instead of evaporating slowly, most of the water becomes run-off and moves into sewers and storm drains. 5

6. Problems caused by UHI
Heat Stroke: Excessive heat can kill, especially the elderly and young children and those without access to AC.
This happens more in urban areas because due to UHI there is no relief from the heat at night.
Greater use of cooling systems in the summer = more energy used 6

7. Fixing UHI Green roofs Green space in urban areas
Different materials used for roads and buildings

8. Urban Air Pollution Two Major Factors: 1. Quantity of pollution
-more in LEDC than MEDC, why?
2. Wind dispersal

9. Causes of Urban Air Pollution
Cars and other transportation
Soil erosion (loess in Beijing)
Burning of fossil fuels ESPECIALLY coal!

10. Beijing Biggest cause is coal during heating season
Season is highly regulated by the government to control some of this
Adds soot sulpher dioxide to the air
Worse when high pressure zone keeps pollution near the surface

11. Beijing: Secondary Causes
More Cars
Soil Erosion
Areas around the city are clay which erodes to a fine dust and blows over the city
Some of the problem has been solved by planting trees around the city.
Industry
Benzopyrene, a lung-cancer causing chemical, is released from some factories
Factories do not have the emission controls standards like factories in the US.

12. Los Angeles Biggest cause is cars and transportation
Urban sprawl means few people live near work
Poor public transit system
This causes photochemical smog
Gases from car exhaust get trapped and heated by strong sunlight forming a brown fog.
Hot, dry environment with little wind makes this worse

13. Solving LA Air Pollution
South Coast Quality Air Management District
Made and enforced car and factory emissions regulations
Public programs to encourage car-pooling
Public programs to encourage 0 pollution cars (electrics)

14. UHI and Rainfall
The extra heat can cause upward movement in the atmosphere which can lead to more storm activity
Local low pressure during the day keeps damp air trapped causing more cloud formation
Overall, cities tend to have higher rainfall averages than surrounding areas.

15. Urban Wind Urban topography can both increase and decrease wind.
On the surface, tall buildings can create “urban canyons” which cause wind to gust through these areas.
This often causes litter and fine particles of dirt and soot to blow around the area on dry days.

16. Urban Wind Urban topography can both increase and decrease wind.
Overall, cities often have LESS wind in the atmosphere due to tall buildings blocking and slowing down wind speed.
This keeps winds from dispersing pollution or cooling the UHI