- 1. Urban Microclimates Studying the impact of urban features on
climatic variables
2. Answers
- Urban area- area of high density buildings with urban
associated services - i.e. motorways and major roads, high rise
buildings, large and densely packed population
- Microclimate- localised and generalised climatic conditions
that have been altered by a physical feature
- Climatic variables- temperature, humidity, precipitation, air
quality, wind direction and speed
3. How does an urban area influence climate
- ACTIVITY - 10 minutes - work in small groups and devise an
explanation of how each of the below impact on
heat/temperature/humidity/wind/precipitation - one person from each
group to explain to the class
- People, cars, buildings (type and size) and roads, vegetation,
size and quantity of water surfaces, drainage, higher density of
pollutants (atmospheric)
4. Definition of a heat island
- An area closely allied with a high density of building in which
we find a microclimate generally consisting of higher heat, lower
wind speed, localised changes in precipitation and lower humidity
than surrounding areas
5. Climatic domes
- Used to describe the DOME of air over a city - the upper levels
of the urban heat island
- Contains more dust, more CO2, more pollutants, less water
- Caused by - the man made surfaces which store and re-radiate
heat later in the day
- Most extreme example - Atlanta
- In general a year round difference of a minimum of 3 to 5
degrees is seen
6. Atlanta
- Atlantas heat island is so intense it generates its own
convectional thunderstorms
- 1997 - daytime local air temp = 27
- Ground surface in city = 49
- 2 till 4 am - air = 10 to 13 degree average
7. Atlantas heat island
- Landsat images pick up over 48 degrees in car parks, yet only
32 in tree islands within those car parks - evapoT reduces
temperature
- How do we solve the problem??
In this false colour image of Atlanta, trees and other
vegetation appear red and buildings, streets and other urban land
covers appear white or blue-green to almost black in colour. The
lighter the colour the hotter the surface 8. How does Atlanta
create storms?
- As heat is trapped in the city (less wind) and the city itself
emits heat, warm air rises
- Cumulo-nimbus form (result of convection in atm)
- As clouds rise and cool they condense to form rain
- Typical convectional thunderstorms (nb tropical rainforests) -
intense and short lived - not always in the afternoon
9. Why do heat islands matter?
- The Georgia heat island costs residents $25 per year
- More electricity is needed for air conditioning systems
- The power company must create the ability to produce extra
power when needed on the few days a year - therefore it costs more
year round
- Lack of vegetation - normally indicates presence of other
problems (increased pollution, runoff problems etc)
10. Solutions
- Installing highly reflective roofing
- Using less asphalt for pavements - brighter surfaces reflect
heat
- Air quality legislation (not as politically likely as the other
options)
11. Lesson Work
- Page 73 in the TEXTBOOK please do questions 1 and 2
- These will be taken in - what you have not finished in the
lesson please finish for homework
- FULL QUESTIONS TO BE HANDED IN ON FRIDAY - REASONS FOR LATE
WORK MUST BE EMAILED TO ME BY WEDNESDAY