Transcript Chapter 2 - TeacherWeb

• Air molecules are
constantly moving and
bouncing off of surfaces
• Each time an air
molecules bounces off an
object, it pushes, or
exerts a force on that
object
• Air pressure: the force of
air molecules pushing on
an area
• The greater the amount
of air molecules, the
greater the air pressure
• Air pressure and density
are higher at sea level
because a greater
amount of air pushes
down.
• Air pressure and density
are lower at a high
altitude because less air
pushes down.
• Therefore, the air at sea
level is denser than at
higher altitudes.
• Air moves from areas of
higher pressure toward
areas of lower pressure.
• You can measure air
pressure with a
barometer.
• A Barometer’s chamber
contracts when air
pressure increases. It
expands when air
pressure decreases.
• Weather is the condition
of the Earth’s atmosphere
at a particular time and
place.
• Wind is air that moves
horizontally (or parallel) to
the ground.
• Differences in air
pressure cause winds.
• 1. Sunlight strongly heats an area of ground. The ground heats the
air. The warm air rises, and an area of low pressure forms.
• 2. Sunlight heats an area of ground less strongly . The cooler, dense
air sinks slowly, and an area of high pressure forms.
• Air moves as wind across the surface, from higher toward lower
pressure.
• Global winds
travel thousands
of kilometers and
lasts for weeks.
• Uneven heating
between the
equator and the
north and south
poles cause global
winds.
• The Earth’s rotation changes
the direction of winds and
other objects moving over
Earth. This is called the
Coriolis Effect.
• Global winds curve as Earth
turns beneath them.
• Winds in the Northern
Hemisphere curve to the right.
• Winds in the Southern
Hemisphere curve to the left.
• Global wind belts-The 3 routes
in which global winds travel the
Earth
Calm Regions
1. Doldrums: Warm air rises at
these low pressure zones
near equator & spreads out
toward the poles. Clouds &
heavy rain. Fuels tropical
storms.
2. Horse Latitudes: Warm air
travels away from equator
then cools and sinks at these
high pressure zones located
about 30 degrees North and
South of the equator. Clear
and dry weather.
Wind Belts
1. Trade Winds: blow from the
East, moving from horse
latitudes toward the equator
2. Westerlies: blow from the
West, moving from horse
latitudes toward the poles
3. Easterlies: blow from the
East, moving from the polar
regions towards the midlatitudes.
• Usually flow from west to
east for thousands of
kilometers
• Speeds greater than 200
km/hr or 124 miles per
hour
• Form because of uneven
heated Earth’s surface
• Each hemisphere has two
jet streams
• Helps make weather
predictions
• Effect air-travel time
• Warmer air rises over land during the day and
cooler air blows in from water.
• Cooler air blows out from the land and warmer
air rises over water at night
• Mountain slopes heat up and cool down faster than the
valleys below them, so that winds flow up the slopes
during the day and night.
• Bodies of water heat up and cool down slower than land,
so that winds flow inland during the day and toward the
water during the night
• Winds that change direction with the seasons are called
Monsoons
winter monsoons originate over land and
are cool and dry
summer monsoons originate over water and are
moist and bring heavy rains
• Evaporation: liquid water becomes a gas or vapor
• Condensation: vapor becomes a liquid, forms clouds
• Precipitation: liquid water flaws to surface in any form
(rain, sleet, snow)
• Humidity is the
amount of water
vapor in the air, varies
place to place and
from time to time
• Saturation: condition
in which the rates of
evaporation and
condensation are
equal
• Compares the amount of water vapor in air with the maximum
amount of water vapor that can be present at that temperature
• Example: air with 50% relative humidity has half the amount of water
needed for saturation
• Dew point is the temperature at which air with a given amount of
water vapor will reach saturation
• Cirrus (curl of hair) appear feathery or wispy and are high altitude
cirrocumulus and cirrostratus
• Cumulus (heap or pile) are very tall and are medium altitude
• Stratus (spread out) form in flat layers and are low altitude
• Fog is close to ground, smooth appearance
• Precipitation is formed
when water vapor
droplets combine with
one another. The droplets
must become larger and
heavier in order to fall.
• Scientists use a rain
gauge to measure
amount
• Snow is measured using
a ruler
• Rain and drizzle form from
water droplets or ice crystals
that melt as they fall to the
ground
• Freezing rain is rain that
freezes when it hits the ground
or other surfaces
• Sleet is rain that freezes into
ice pellets while falling through
cold air
• Snow forms ice crystals that
merge in clouds
• Hail forms when ice pellets recirculate in the clouds until
they get too heavy and fall to
ground
• Sulfur dioxide and
Nitrogen oxides enter the
air as pollution and
combine with water vapor
to form acids.
• The acids mix with cloud
droplets or ice crystals
and fall as precipitation
• Effects plants, animals
and water
.