A mixture of gases that surrounds the Earth
is called the atmosphere. The atmosphere protects us from the sun's
rays that are harmful, in addition they contain the oxygen we need to
survive. The atmosphere is split into five layers troposphere being the
lowest layer and the uppermost atmospheric layer being the thermosphere.
Troposphere is the densest atmospheric
layer. It contains about 90 percent of the atmosphere's total mass. The
troposphere is the layer in which we live in.
Stratosphere is above the troposphere.
The air is very thin and contains little moisture. The lower stratosphere
is extremely cold, measuring about -60 degrees Celsius.
Mesosphere is the coldest layer of
the atmosphere. Temperatures can be as low as -93 degrees Celsius.
Thermosphere is the uppermost atmospheric
layer. Temperatures in the thermosphere reach 1,700 degrees Celsius.
Ionosphere are the electrically charged
particles found in the upper part of the thermosphere. Ionosphere stems
from the word ion that means electrically charged particles.
The
energy in the atmosphere that is transferred as electromagnetic
waves through the sun is called radiation. In the atmosphere the transfer
of heat by the movement or circulation or movement of a liquid or
gas is called convection. On the contrary the transfer of heat from one
material to another by physical contact is called conduction.
Atmospheric Winds
and Pressure
Pressure Belts:
When warm air rises over the equator it begins to cool. Then it stops
rising and moves toward the poles. Then at 30 degrees north and 30 degrees
south latitude, a certain amount of the cool air begins to sink.
This sinking causes a high pressure belt near 30 degrees north and 30 degrees
south latitude.
Coriolis Effect: When the Earth rotates it
causes the wind to travel in a curved path rather than in a straight
line. The curving of moving objects like wind by Earth's rotation is called
the Coriolis effect.
Trade Winds:
In both hemispheres, the winds that blow from 30 degrees latitude from the
equator are called trade winds. The Coriolis effect causes the trade
winds to curve.
The Doldrums and Horse Latitudes: Trade winds
of Northern and Southern Hemispheres meet in an area of low pressure
around the equator called the doldrums.
Sinking air crates an area of high area called horse latitudes. Here the
winds are weak.
Westerlies: Wind belts found in both the
Northern and Southern Hemispheres between 30 degrees and 60 degrees
latitude. They flow toward the poles in opposite direction of the trade
winds.
Polar Easterlies: Wind belts that extend
from the poles to 60 degrees latitude in both hemispheres. They are
formed from sinking, cold air moving from the poles toward 60 degrees
north and 60 degrees south latitude.
Jet Streams: Narrow belts of high speed
winds that blow in the upper troposphere and lower stratosphere.
Local Winds: An area's geography for example
a mountain or a shoreline sometimes produces temperature differences
that cause local winds like land and sea breezes.
Click Here for Cool Activities on the Atmosphere!
Here are some more web sites about the Atmosphere:
http://www.pbs.org/wgbh/nova/balloon/science/atmosphere.html
http://liftoff.msfc.nasa.gov/academy/space/atmosphere.html
http://csep10.phys.utk.edu/astr161/lect/earth/atmosphere.html