The Earth’s atmosphere sustains life, forms a protective shield that filters out harmful radiation, and protects the Earth from the constant shower of small meteors.
The atmosphere consists of gases and trace amounts of suspended particles from volcanoes, nuclear explosions, and industrial pollutants.
99% of the gases occur within 20 miles above the surface of the earth.
The most abundant gas is nitrogen (78.1%), followed by oxygen (20.9%), argon (.9%), carbon dioxide (.03%).
Water vapor is a variable component of the atmosphere, from 0.05% to 4%.
Ozone is continuously being produced in the Earth’s atmosphere by the interaction of the Sun’s radiant energy with oxygen molecules.
O2 + energy -> 2 O
O2 + O -> O3
Ozone is concentrated in the stratosphere. Ozone absorbs ultraviolet radiation from the sun.
Primary pollutants of the atmosphere are nitrogen oxides from fuel combustion, volatile organic compounds, sulfur oxides, particulates, and carbon monoxide.
Secondary pollutants are acid rain and photochemical smog.
2. Changes in Pressure in the Atmosphere
Pressure is created by the weight of the air above pushing down. Air pressure decreases with height.
Structure of the Atmosphere
Troposphere – means “turning over,”
Contains about 80% of all the mass of the atmosphere and extends from ground level to 8 to 18 km
Thickest near the equator and thinnest at the poles
All weather occurs in troposphere
Pressure and temperature decreases in the troposphere
Tropopause – boundary between the troposphere and the overlying stratosphere, important in the formation of the jet stream
Stratosphere – to smooth out, above the height of most clouds, to an altitude of about 30 miles
Very stable with very little turbulence
Temperature increases in the stratosphere
79% nitrogen, 20% oxygen and 90% of all atmospheric ozone
Ozone makes up .001% of the molecules of gas, yet is vital for life on Earth
Ozone helps prevent harmful ultraviolet radiation from reaching the earth’s surface
Mesosphere – the layer where incoming meteors first begin to burn
Temperature decreases, the coldest layer as low as -148 oF
Thermosphere (62 miles), also called the ionosphere
Air is very thin
Solar wind bombards gas molecules
During high sunspot activity the temperature can rise as high as 2237 oF and in low sunspot activity 437 oF
Radio waves bounce off the ionosphere
Electrical disturbances in the ionosphere form the auroras
4. Earth’s Motions
Rotation – daily cycle of sunlight and darkness
Revolution – movement of the Earth around the sun, 113,000 km/hr
The Earth is closest to the sun in winter, farthest in summer
Summer solstice – longest day in the Northern Hemisphere, Earth tilted toward the sun
Winter solstice – shortest day in the Northern Hemishere, Earth is tilted away from the sun
Equinoxes ( Spring or Fall) – 12 hours of daylight and 12 hours of night everywhere on Earth
5. Earth’s Tilt, 23.5 degrees
The tilt of the Earth is the reason for the seasons
6. Length of Daylight
The length of daylight in the Northern Hemisphere is greater than the length of darkness in summer. The farther north you go, the longer the period of daylight. On the summer solstice on the Arctic circle the length of daylight is 24 hours!
7. Heat is the transfer of energy due to temperature differences, heat flows from hotter to colder
Conduction – transfer of heat energy through matter by molecular motion
Convection – transfer of heat energy by the mass movement of matter
Convection is important in distributing heat energy from the tropics to the poles
Convection takes place in the mantle, in water, and in the atmosphere
Radiation – radiant energy that travels through outer space in the form of electromagnetic radiation
8. Solar Radiation
When radiation strikes an object some of the radiation can be absorbed, some can be transmitted, and some may be reflected.
The blue sky s a result of scattering.
About 50% of the incoming radiation is absorbed.
9. Greenhouse Effect – water vapor and carbon dioxide absorbs the longer wavelengths re-emitted by the earth
Necessary to make life suitable on Earth
10. Variations in Temperature
Latitude – the tropics are warmer and the poles are colder
Isotherms are lines that connect points of equal temperature
Isotherms run from east to west
Land and water – areas by large bodies of water experience more moderate changes in temperature throughout the year. In addition, the range daily highs to daily lows will not be as great as in areas surrounded by land.
Geographic position – a city with the prevailing wind blowing from the ocean will experience cooler, wetter climates than a coastal community with the prevailing wind blowing from the land
Altitude – increasing in altitude is similar to increasing in latitude, the higher the attitude, the colder the climate
Albedo is the fraction of total radiation reflected by any surface. Darker objects have a lower albedo than lighter objects.
Clouds have a high albedo and reflect sunlight back into space.
At nighttime clouds act as a blanket and have a warming effect.