The Atmosphere of Earth Adapted from McGraw Hill Higher Education

The probability of a storm can be predicted, but nothing can be done to stop or slow a storm. Understanding the atmosphere may help in predicting weather changes, but it is doubtful that weather will ever be controlled on a large scale.

The Atmosphere

Composition of the Atmosphere Nitrogen (N2)is the most abundant gas in the Earth’s atmosphere making up about 78 %. Oxygen is the second most abundant making up about 21 %. Nitrogen cycles in the atmosphere through the Nitrogen Cycle as it is removed from the atmosphere by bacteria and lightening These nitrogen compounds are then taken up by plants and utilized in growth and development.

Oxygen (O2)also cycles in the atmosphere Living organisms are used as food sources and oxygen is utilized in most organisms that digest other organisms Chemical weathering of rocks can cause oxides to form, locking up the oxygen with minerals. Oxygen is released into the atmosphere by plants as they photosynthesize.

Water in the atmosphere varies considerably and also cycles in the Hydrologic or Water Cycle. This is the cycle of evaporation and condensation that results almost daily. Carbon Dioxide (CO2)makes up approximately 0.03 % of the Earth’s atmospheric gases. Carbon dioxide concentrations in the atmosphere is regulated by the Carbon Cycle: Removal of CO2 from the atmosphere as green plants fix the CO2 into carbohydrates Exchanges of CO2 between the atmosphere and the oceans Chemical reactions between the atmosphere and limestone

Earth's atmosphere has a unique composition of gases when compared to that of the other planets in the solar system.

Atmospheric Pressure The atmosphere exerts pressure on the Earth that decreases with increasing altitude This is due to the fact that with increasing altitude, there is a decrease in the column of gases above the Earth’s surface This is the same that happens as you go deeper into the ocean, the pressure increases as you add more water on top of you.

At greater altitudes, the same volume contains fewer molecules of the gases that make up the air. This means that the _______ of air decreases with increasing altitude. density

The earth's atmosphere thins rapidly with increasing altitude and is much closer to the earth than most people realize.

The mercury barometer measures the atmospheric pressure from the balance between the pressure exerted by the weight of the mercury in a tube and the pressure exerted by the atmosphere. As atmospheric pressure increases and decreases, the mercury rises and falls. This sketch shows the average height of the column at sea level.

Warming the Atmosphere The temperature of an object is actually a measure of the kinetic energy of the molecules that make up the object. Any object that contains any kinetic energy at all (i.e. has a temperature above absolute 0K gives off radiant energy.

On the average, the earth's surface absorbs only 51 percent of the incoming solar radiation after it is filtered, absorbed, and reflected. This does not include the radiation emitted back to the surface from the greenhouse effect, which is equivalent to 93 units if the percentages in this figure are considered as units of energy.

Structure of the Atmosphere Observed lapse rate. The temperature decreases approximately 6.5 OC for each km of alitude (3.5 OF/1,000 ft) (-6.5 OC /1 km) Inversion When a layer of the atmosphere increases with altitude. (Reverses typical direction-more examples later) Troposphere The layer of the atmosphere closest to the surface of the Earth. Up to a height of about 11 km (6.7 mi) Air is constantly mixed due to denser air being above less dense air. More on this later. Most of the water vapor and therefor clouds are located in this layer.

On the average, the temperature decreases about 6 On the average, the temperature decreases about 6.5OC/1,000 km, which is known as the observed lapse rate. An inversion is a layer of air in which the temperature increases with height.

Stratosphere Temperature begins to increase with height. Very stable as denser air is below less dense air. Up to about 48 km (30 mi) Temperature increases as a result of interactions between high energy UV radiation and ozone (O3) Airplanes fly in this layer to avoid turbulence. Some birds and bacteria are found here!

Ozone shield (not a layer) A layer of ozone that absorbs much of the ultraviolet radiation that enter the atmosphere and provides a significant shield to the Earth below from damging UV radiation 90% is located in the Stratosphere. This is the layer scientists observed was thinning due to the influx of chlorofluorocarbons which were used extensively in refrigeration. CFCs have since been banned.

Mesosphere Temperature again begins to decrease due to a decrease in gas molecules to absorb radiation Most meteors burn up in this layer protecting the Earth. Thermosphere Temperature again begins to rise due to the presence of molecular fragments which absorb radiation from space-it is extremely high here. Very little energy transfers, however, due to the lack of molecules (very few molecules to collide with objects) The International Space Station orbits here The auroras occur here-aurora borealis or northern/southern lights

Exosphere Outermost layer of the atmosphere where molecules merge with the vacuum of space. Satellites are placed here due to low friction. Earth’s gravity holds most of the molecules in; some escape into space. The high kinetic energy of the molecules at this height are significant enough to cause them to be able to escape into space. Ionosphere Alternative name for the thermosphere and upper mesosphere. Due to the occurrence of free electrons and ions (charged particles). It is the electrons and ions in this layer that cause radio waves to be able to be reflected around the world.

The structure of the atmosphere based on temperature differences The structure of the atmosphere based on temperature differences. Note that the "pauses" are actually not lines, but are broad regions that merge from one layer to next.