The Atmosphere
Atmosphere
and Climate
I.
Atmosphere is a thin layer of gases that covers the earth
a. Composition
of the Atmosphere
1. 78% Nitrogen
2. 21% Oxygen
3. 1% other substances such as water vapor, argon, carbon dioxide, neon, helium
II. Weather
1. Weather is the state of the atmosphere over a short period of time
2. Constantly changing
III. Climate
1. Climate is over a long period of
time
2. Generalized, an aggregate or composite of weather based on many years of weather records
IV. Elements of weather and
climate
1. Properties that are measured regularly
2. Most important elements
a. Temperature
b. Humidity
c. Cloudiness
d. Precipitation
e. Air pressure
f. Wind speed and direction
V. Atmospheric Pressure
1. All atoms and molecules have
mass and the closer to the Earth they
are, the more closely packed they are,
which means they exert more force
a. Air pressure varies from place to place
b. On average the air pressure is 14.7 lbs per square inch
c. The Force of this air is measured with
a Barometer
*Anaroid Barometer is a small box with most of the air removed; as air pressure increases or decreases
a gauge that is attached will
shift
*Mercury Barometer is much more
accurate but too large; it is a large
inverted cylinder that is placed in a large tray of mercury; as
pressure increases, more mercury is forced into the cylinder and vice versa
Composition of
the atmosphere
A. Air is a mixture of gases
B. Major components of
clean, dry air
1. Nitrogen (N): 78%
2. Oxygen (O2): 21%
3. less than 1%: Argon and other gases: less than 1%
4. Carbon dioxide (CO2): 0.035% - absorbs heat energy from Earth
C. Variable components of
air
1. Water vapor
a.
Up to about 4% of the air's volume
b.
Forms clouds and precipitation
c.
Absorbs heat energy from Earth
2. Dust
a.
Includes pollen and spores
b.
Water vapor condenses on
c.
Reflects sunlight
d.
Helps color sunrise and sunset
3. Ozone
a.
Three atom oxygen (O3)
b.
Absorbs harmful UV radiation
c.
Distribution not uniform
d.
Human activity is depleting ozone by adding chlorofluorocarbons (CFCs)
Structure of
the atmosphere
a. Troposphere
extends from the surface to about 6 miles
1. this contains about 90% of the Earth’s gasses
2. this is where most weather occurs
b. Stratosphere
extends about 30 miles above the Earth
1. The winds in the stratosphere don’t swirl and are not as dramatic in this
layer
2. Commercial airliners usually travel in the lower levels of this layer
3. The Ozone is contained in
this layer, which protects us from
harmful u.v. Radiation
c.
The Mesosphere
extends to approx. 50 miles above the Earth’s surface
d.
The Thermosphere
extends after the Mesosphere up to 310 miles
e.
The Exosphere
and Ionosphere
then fade out to space beyond the Thermosphere
Air Mass
1. Air Masses are formed when a large part of
the troposphere stops or moves very slowly over a land or water surface
2. Same properties as the region it is formed
over
3. These can be over thousands of kilometers
wide and long
Types of Air Masses
c = Continental air mass/usually dry air
formed over land
m =
Maritime air mass/ usually moist and formed over oceans
P =
develope over high latitudes and cool due to the polar regions
T =
develope over low latitudes (equator), and warm due to the tropical region
EXAMPLES;
mP
= cool, moist
cP
= cold, dry
mT
= warm, moist
cT
= dry, hot
NOTE;
remember that the lower case letter is
always first in this code
Results when Air Masses meet
A. When two air masses meet they usually do not
mix
1. they
form a boundry which is called a front
2. Fronts
often cause stormy weather
Example;
WARM FRONT
1. Developes
when a warm air mass meets a cold air mass
2. The
less dense warm air sllides over the
cold air mass
COLD FRONT
1. Cold
air mass meets a warm air mass
2. cold
air forces the warm air up
quickly
OCCLUDED FRONT
1. When
two cool air masses merge forcing the
warmer air between them to rise
Winds Provided by Air Masses
Anticyclone
= formed by a high pressure area
1. the
air circulates away from the center
a. this is clockwise in the northern hemispher
and counter clockwise in the southern hemisphere and it usually provides
fair weather
Cyclones
= formed by a low pressure area
1. "Looks
like" a bowl in the air mass
2. The
air flows in a counter clockwise motion
and clockwise in the Southern hemisphere
and it usually provides stormy weather