|
Elevation | Orography
This section examines the effects of the
contours and colors of the Earth's surface on climate. See also 3.2.1 Sun
and the Global Energy Balance
Elevation
Altitude influences climate. The higher (or farther away from
the earth's surface) a place is, the cooler its temperature. This
is because the sun's rays pass through the atmosphere and are absorbed
by the Earth's surface where they are changed into heat energy.
Altitude of Landforms
The heat energy is released into the air around the Earth's surface.
The further away from the surface, the cooler the air. The rule
for temperature loss due to altitude is as follows: the temperature
of dry air decreases 1Celsius degree (1 Co) for every 100 meters
of altitude.
The amount of water vapour in the air affects the temperature.
The temperature of air saturated with water vapour only changes
0.6 Co for every 100 meters of altitude.
As air rises, it cools and its water vapour condenses. The air
loses its ability to hold its moisture content (T - frontal precipitation).
At some point precipitation occurs. When air meets a mountain,
the air must flow over the contours. As it moves up the contours
of the mountain, the air cools, condenses, and falls as precipitation.
The drier air continues up and over the mountain and follows the
contours downwards. This precipitation is called orographic or relief
precipitation.
(NOAA)
If however there are few contours on the surface, the air flows
across it easily and retains its moisture. Large exposed landmasses
such as continents heat up quickly. Air flowing over the prairies,
for example, is heated quickly. The hot air will rise and as it
does it begins to cool, condense, and precipitate. This is called
convectional precipitation.
Ontario contains rolling features of the eroded Canadian Shield
but no extensive landforms such as high mountains or flat plains
other than the Niagara Escarpment (T - Niagara Glaciation). It
is a cuesta or structure of high cliffs with a short, steep
slope of rock layers edging in one direction and a long gentle
slope down the top of the strata in the opposite direction. The
summit of the escarpment runs the length of Ontario from Queenston
to Tobermory. The steep slope of the Cambrian cuesta does influence
its local climate but, generally speaking, it has little effect
on Ontario's overall climate.
ACTIVITY 1
- Find the Ontario Temperature and Precipitation
maps in Section 5.2.1 that show the last 20 years of climate.
Locate the local rain shadow effect of the escarpment. Hint:
look east because of the Westerlies!
- How are ecosystems affected by altitude?
Draw a profile of the ecosystems for Canada's tallest mountain.
Orography
Orography is the recording of points of equal elevation in an
area to produce a topographic map showing the contours of the land.
A topographical map of the surface of an area shows contour lines
with an equal number of degrees of elevation between them. The
elevation or altitude of an area is a factor that helps determine
the ecosystem found in the area whether above sea level or in depths
underwater.
ACTIVITY 2
- Check for the highest and lowest points
in Ontario. How far are they above sea level?
Hint: sometimes the altitude or elevation above sea level is shown as a number
on road maps
- Find a contour map of Ontario and research
the correlation between the ecosystems found and the change in
altitude or elevation that may be the deciding factor. Hint:
check the Hardiness Zone maps for gardeners.
- What factors other than elevation or altitude
may help determine the ecosystems found in Ontario? Globally?
Content Updated Sept 2005
|
