Transcript What is an atmosphere?

Warm-up
What is the source of energy that drives
convection within the atmosphere and
oceans?
A. Earth’s rotation
B. The sun
C. Hurricanes
D. Heat from the inner core
Weather is the condition of the
Earth’s atmosphere at a particular
time and place
Earth’s
Atmosphere
What gases is Earth’s atmosphere
made of?
Surprisingly, more Nitrogen than Oxygen!
What is an atmosphere?
An atmosphere is the layer of gases
that surround the planet.
Ours is as thin as Earth’s crust!
Layers of the Atmosphere
• The four main layers of the
atmosphere are displayed
on the picture to the right.
• They are classified
according to changes in
temperature.
• Tropo means “turning” or
“changing”. This is where
weather occurs.
– Temperature decreases
with altitude (-6.1oC
for every km)
The layers of
our
atmosphere!
Please Remember:
Exo = satellites
Iono = electric
Thermo = hot
Meso = protecting
Strato = airplanes
Tropo = weather
Exosphere
Ionosphere
Thermosphere
Mesosphere
Troposphere
Stratosphere
Air
Pressure
Properties of Air
• Air consists of atoms and molecules
• Because air has mass, it also has other
properties, including density and pressure.
• Density = Mass / Volume
What is air pressure?
•Air pressure is the result of a column
of air pushing down on an area.
•Denser air exerts more pressure than
less dense air.
(Air pressure = air pushing)
There are two main factors that
affect air pressure.
#1 = Altitude: how high up in the
atmosphere you are.
Oxygen is heavier than Nitrogen, so
it sinks to the bottom of the atmosphere.
That means that the lower you are, the
more weight is pushing on your head!
This also means that the higher your
altitude, the less oxygen there will be
to breathe!
(This is why people take oxygen tanks
when climbing Mt. Everest)
#2 = Temperature: When it is cold, the
oxygen will huddle together, putting
even more molecules on your head!
Cold
High Pressure
Hot
Low Pressure
Measuring Air Pressure
An instrument called a Barometer is
used to measure the changes in air
pressure.
There are two kinds of
Barometers: Mercury barometers
and Aneroid barometers.
Mercury Barometer
•The diagram shows how
a mercury barometer
works.
•A mercury barometer
consists of a glass tube
open at the bottom end
and partially filled with
mercury.
•The space in the tube
above the mercury in is a
vacuum – it contains no
air.
Now we have barometers that don’t
need liquid.
These are Aneroid barometers, and
work based on metal compression.
Aneroid Barometer
• Changes in air
pressure cause the
walls of the airtight
metal chamber to
flex in and out.
• The needle on the
dial indicates air
pressure.
Units of Air Pressure
• There are several different units.
• The U.S. average is just under 30 inches of
mercury (29.52)
• National Weather Service maps indicate air
pressure in millibars
• One inch of mercury equals approximately
33.87 millibars, so 30 inches of mercury
equals about 1,016 millibars.
Isobars
• The wavy lines on a
weather map are often
associated with High
pressure (H) and Low
pressure (L) centers.
• Each line, called an
isobar, connects the
places that have the
same atmospheric
pressure.