Download File - Mr. Champion

Clouds…
and what
they tell us.
13.11
Clouds (p. 530)
• A cloud is a large collection of tiny water droplets.
(100 times smaller than the average rain drop – Fig
2)
• Clouds are formed when warm air rises and then
cools at higher altitudes.
• The cooling causes the water vapour to condense
(collect together) in tiny water droplets.
• As many water droplets collect together, they can
make a rain drop.
• When the rain drop is large enough, gravity causes it
to fall to the Earth.
3 Ways Clouds are Made:
1.
Convective Clouds:
- formed when warm air rises to high altitudes where the
water vapour then cools and condenses forming tiny water
droplets.
2.
Frontal Clouds: (Fig. 3)
- formed when the leading or front edge of a large air mass
meets another air mass of different temperature. The
colder air mass pushes the warmer air up where it
condenses forming tiny water droplets.
3. Orographic Clouds: (Fig. 4)
- When objects, such as mountains, force air
to go up. When the air hits the cooler air at
higher altitudes, condensation occurs.
Fog
• Fog is actually a cloud that forms near the
ground.
• Fog is produced on clear nights when energy
from the surface radiates upward but is not
reflected back to the Earth by any clouds.
• Thus, the air near the ground cools, allowing
water vapour to condense into fog.
Cloud Shapes
The two main cloud shapes are:
Cumulus – a billowing, rounded shape
Stratus – a flattened, layered shape
1) Cumulus Clouds
 Look like big cotton balls in the sky.
 Have very large spaces of clear sky between them.
 Usually indicate unstable conditions
 Normally they don't carry any rain, but can change into
cumulonimbus (thunder) clouds.
2) Stratus Clouds
• Tend to grow horizontally
• Indicate stable conditions
3) Cirrus Cloud are:
 Thin and wispy
 Found very high in the sky
 Point in the direction the wind is blowing
 No precipitation falls from cirrus clouds
 A sign of fair weather
• Nimbus means low level, rainy cloud
• Alto means mid-level cloud (not real high
or low)
• Cirrus means high level cloud
Classification of Clouds
BLM 13.11
The Water Cycle
Chapter 13.8
The Hydrosphere
All of the Earth’s water, both fresh and salt,
forms what is called the hydrosphere.
• Only a small portion of the hydrosphere is
fresh water (2.5%).
• The majority of this fresh water is frozen in
glaciers and polar ice caps, and the rest is
mainly underground, or surface water
(lakes, rivers, etc.)
The Hydrosphere
• 97.5% is salt water
• Canada is one of the luckiest countries in
the world b/c our population is just .5% of
the world total, yet we have almost 10% of
the world’s supply of fresh water.
• B/C so much of the Earth’s surface is
water, our weather systems depend
greatly on it.
WATER CYCLE
(Hydrologic Cycle)
Water on Earth is always changing. Its repeating
changes make a cycle. As water goes through its cycle,
it can be a solid (ice), a liquid (water), or a gas (water
vapour).
How do these changes happen?
WATER CYCLE
• Adding or subtracting heat makes the cycle work.
• If heat is added to ice, it melts. If heat is added to
water, it evaporates.
• Evaporation occurs when liquid water turns into a
gas called water vapour.
• If heat is taken away from water vapour, it
condenses.
WATER CYCLE
• Condensation occurs when water vapour turns into a
liquid.
• If heat is taken away from liquid water, it freezes to
become ice.
•
• Ice changing directly to vapour (skipping the liquid
stage), is called sublimation. (ex. a wet cloth to be
hung outdoors in freezing weather and retrieved
later in a dry state.)
• Transpiration occurs when water evaporates from
plants.
Terms to know
• Evaporation
– the change of state from liquid to gas
– This is the purest naturally occurring water
• Condensation
– The change of state from water vapor to liquid
– Forming cloud stage
• Precipitation
– Water that falls to the ground
– Example: rain, snow, sleet, hail
• Runoff
– The water that flows over the ground surface
• Percolation
– The water that soaks into the ground forming pockets of groundwater. The
downward movement of water through soil and rock
• Sublimation
– Transition from solid to gas (no liquid phase)
• Transpiration
– The loss of water vapor through the leaves of plants into the atmosphere
Hydrologic Cycle = Water Cycle
Questions to Answer
• A glacier may be a thousand years old, yet it is
considered to be “fresh” water. Explain why.
• The Earth’s freshwater supply is being depleted
at an incredible rate. One scheme to combat this
is to tow icebergs from the North Atlantic Ocean.
Speculate on the advantages and
disadvantages of this.