Transcript The Atmosphere

Atmospheric Movement in Weather Change
Weather
 The short-term (a few hours or days)
condition of the atmosphere at a given
location. Water and air move constantly--together they create WEATHER!
– The weather of an area is due to four
atmospheric factors: heat energy, air
pressure, winds, and moisture.
 Meteorologists are
scientists who study
and predict the weather
Weather is the condition of
Earth’s atmosphere at a
particular time and place.
Composition of the Atmosphere
Oxygen and nitrogen = 99% of dry air.
 Carbon dioxide and argon make up most of the
other one percent (1%).
 The remaining gases are called trace gases
because only small amounts of them are present.
Composition of the
Atmosphere
 Nitrogen is the most abundant gas in the
atmosphere
– Makes up a little more than three fourths of
the air we breathe
– Essential to living things
 Most living things cannot obtain nitrogen directly
from the air
– Bacteria convert nitrogen into substances
– Plants then absorb the nitrates from the soil and use
them to make proteins.
– Animals must eat plants or other animals.
Getting Energy
All energy on Earth comes
from the Sun
Radiation – is the
absorption of energy.
Energy travels from the sun in
electromagnetic waves.
These waves are absorbed by
the things on earth.
Heat is transferred
to the air when
the air touches
the ground.
(Ground is warmed by radiation)
The warmer something
gets the more energy its
molecules have.
The more energy
molecules have the faster
they move.
The faster molecules
move the more volume
(space) they take up.
Basic Ingredients for Weather
The solar radiation
heats the surface of
the earth.
Heat is transferred to air molecules that
come in contact with the ground.
As the
Hot Air Rises…
Cooler air is
pulled in from
other places
Do you know
what this is
called?
Air Pressure
 Air pressure occurs as a result
of the weight of the air
pressing down on the Earth.
Caused of course by Earth’s
gravity.
 A change in air pressure
usually indicates a change in
weather is going to occur.
 A body of air that has similar
temperature, humidity, and air
pressure is called an air mass.
Air pushes in all directions—down, up, and sideways
There is a
column of air
above you all the
time. The weight
of the air in the
atmosphere
causes air
pressure.
As the
air
becomes
less
dense it
rises
Ground warmed by radiation
Rising air spreads
heat throughout
the atmosphere.
Ground warmed by radiation
Increasing Altitude
 Altitude, or elevation, is the distance
above sea level
 Air pressure decreases as altitude
increases.
 As air pressure decreases, so does
density.
Why does air pressure decrease
as altitude increases ?
 If you are on the top of a mountain, the air
pressure is lower because the column of air
above you is shorter.
 If you are at sea level, the column of air is
taller (pushing down on you), and that
means there is more air pressure.
Air Pressure
 An air mass with low pressure
is likely to be stormy.
 An air mass with high pressure
is likely to be fair.
 Air moves from areas of high
pressure to areas of low
pressure.
 This movement occurs as the
differences in air pressure
cause wind.
The Wind
 Winds are the result of uneven
heating of the Earth’s surface
 This uneven heating
causes differences
in air pressure
to develop.
Where Does Wind Go?
 Winds always
blow from areas
of high pressure
to areas of low
pressure.
– The closer wind
is to the low
pressure area
the faster it
blows.
Moves pressure
systems from West to
East.
Atlantic
Ocean
Pacific
Ocean
Gulf of
Mexico
Air Masses
Air masses are large
bodies of air classified by
their temperature (warm
or cold) and amount of
water (wet or dry).
Warm Front
COLD FRONT
Stationary Front
Occluded Front