Download Water and Wind Power Point

The Atmosphere
Section 2
The Water Cycle
〉What happens to water in the troposphere?
〉Water is continuously being moved through the
troposphere.
• water cycle: the continuous movement of water
between the atmosphere, the land, and the oceans
• Water is continuously being moved, primarily between
the oceans and the continents.
The Atmosphere
Section 2
The Water Cycle, continued
• Evaporated water vapor condenses to form precipitation.
• Evaporation occurs when solar energy heats water
molecules, and they rise as gaseous water vapor.
• transpiration: the process by which plants release
water vapor into the air through their leaves
• precipitation: any form of water that falls to Earth’s
surface from the clouds
The Atmosphere
Section 2
The Water Cycle, continued
• Air contains varying quantities of water vapor.
• humidity: the amount of water vapor in the air
– Relative humidity is the actual amount of vapor in the
air compared to the maximum amount the air could
hold at that temperature.
• Air that has a relative humidity of 100% is said to be
saturated.
The Atmosphere
The Water Cycle, continued
• Warmer temperatures
evaporate more water.
– Warm air can hold
more water vapor than
cold air can.
• Water vapor becomes
liquid at the dew point.
Section 2
The Atmosphere
Section 2
The Water Cycle, continued
• The higher the humidity, the higher the dew point.
• dew point: the temperature at which the rate of
condensation equals the rate of evaporation
– Air or a gas begins to condense to a liquid.
• When humidity is high, there are more molecules of
water in the air and it is easier to form liquid.
The Atmosphere
Section 2
The Water Cycle, continued
• Clouds form as warm, moist air rises.
– Water vapor condenses into tiny droplets of liquid as
it cools.
– Depending on where clouds form, they can have
different shapes and characteristics.
The Atmosphere
Section 2
The Water Cycle, continued
• Cloud names describe their shape and the altitude at
which they form.
– Clouds are named with combinations of three root
words:
• cirrus
• stratus
• cumulus
• Cirrus clouds are thin, wispy, and occur at high altitudes.
• Stratus clouds are layered and look like sheets.
• Cumulus clouds are white and fluffy with somewhat flat
bottoms.
The Atmosphere
Section 2
The Water Cycle, continued
Cloud names reflect combined characteristics.
• Cirrostratus clouds are high, layered clouds that form a
thin white veil.
• Altostratus and altocumulus clouds are stratus and
cumulus clouds that occur at middle altitudes.
• Cumulonimbus clouds are towering rain clouds that often
produce thunderstorms.
• Nimbostratus clouds are large, gray clouds that often
produce steady precipitation.
The Atmosphere
Cloud Types
Section 2
The Atmosphere
Section 2
Air Pressure
〉What is air pressure, and by what terms is it also
known?
〉The barometric pressure, also called
atmospheric pressure or air pressure, is the
pressure that results from the weight of a column
of air extending from the top of the
thermosphere to the point of measurement.
The Atmosphere
Section 2
Air Pressure, continued
• Changes in barometric pressure often accompany
changes in the weather.
• Falling pressure may indicate that a large air mass is
leaving the area.
• Rising air pressure may mean that an air mass is
moving in.
The Atmosphere
Section 2
Wind
〉What causes wind?
〉Differences in pressure create winds.
• Pressure gradients cause air to move.
– pressure gradient: a difference in air pressure from
one place to another
– The air in a pressure gradient moves from areas of
high pressure to areas of low pressure.
– wind: the movement of air from a high-pressure area
to a low-pressure area
The Atmosphere
Section 2
Wind, continued
• Earth’s rotation affects the direction of winds.
• Coriolis effect: the curving of the path of a moving object
from an otherwise straight path due to Earth’s rotation
– Points at different latitudes on Earth’s surface move at
different speeds.
• Earth goes through a full rotation in 24 hours.
• Points on the equator travel the Earth’s full
circumference in 24 hours.
• Points closer to the poles do not travel as far.
The Atmosphere
Section 2
Wind, continued
• Predictable air circulation forms wind patterns.
– Winds in the Northern Hemisphere curve clockwise.
– Winds in the Southern Hemisphere curve
counterclockwise.
• The resulting patterns are very regular, and have been
named by meteorologists.
– Polar easterlies
– Westerlies
– Northeast trade winds
– Southeast trade winds
The Atmosphere
Circulation Patterns
Section 2
The Atmosphere
Section 2
Wind, continued
• Global wind patterns form circulation cells.
– Flowing from a high-pressure area to a low-pressure
area, air flows both north and south in a large loop.
– Three loops of rising warm air and sinking cold air can
be found in each hemisphere.
– Air in each of the hemispheres completes three loops,
called cells.