 Australia's
three main climate zones
CLIMATE ZONES FOR URBAN DESIGN
Since the aim of climate-sensitive urban design is to provide the most comfortable
thermal environment possible, the definition of climate zones for urban
designers obviously has to be done by considering the climate variables
which affect human comfort.
These variables are temperature, humidity or water vapour content of
the air, heat radiated from the sun and from our surroundings and wind
speed. Whether we feel too hot, too cold or (like the baby bear's porridge
in the fairy tale) "just right", depends on the combined effect of these
five quantities.
The heat radiated from our surroundings (terrestrial radiation) and
the wind speed can vary considerably over small distances. For simplicity,
only temperature and water vapour content of the air (humidity) have been
used in the criteria for defining the climate zones.
A description of each climate zone and the definition used to set the
boundaries on the map, follow.
Temperate Climate
The temperate climate has mild to warm summers and cool winters. The need
for winter home heating is greater than the need for summer cooling. It
is a relatively comfortable climate, especially near the coast, where summers
are cooler and winters warmer than further inland. In the mountains of the
Great Dividing Range, winters are cold and summers are pleasantly mild.
Definition for zone boundary: mean January maximum
temperature <= 30 degrees Celsius (Australian research suggests a
temperature of 29.5 degrees Celsius as the upper limit for human thermal
comfort) AND 3 pm January water
vapour pressure <= 2.1 kPa (this is about the upper humidity limit
for thermal comfort: the American Society of Heating, Refrigerating and
Airconditioning Engineers use 1.87 kPa as the upper limit).
Hot Dry Climate
In this climate, summers are hot to very hot and it seldom rains. Winter
days may be cool or warm, and winter nights can be very cold. The air is
dry, there is little cloud; sunshine is intense and glare can be a problem.
There is a big temperature difference between day and night.
Definition for zone boundary: mean January maximum
temperature > 30 degrees C AND 3 pm January water
vapour pressure <= 2.1 kPa)
Warm Humid Climate
Summers in this climatic zone are warm, and very humid. In most parts of
the zone, summer will be rainy. Winters are warm, dry and sunny. Coastal
areas are subject to tropical cyclones (also known as hurricanes). The summer
climate is stressful. It is the least comfortable Australian climate. The
body's natural cooling system (the evaporation of perspiration) does not
work well, because the air is already so full of water
vapour that it cannot hold much more.
Definition for zone boundary: mean January water
vapour pressure >= 2.1 kPa (most places meeting this criterion
also have a wet bulb temperature
of about 24 degrees Celsius or more, which is the upper limit for any
effect from evaporative cooling).
|
