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