Atmosphere – The layers of air from the planet’s surface to outer space.

Key Ideas about the atmosphere:  Without the atmosphere, you would have no oxygen to breathe.  The two main gases in the atmosphere are Nitrogen (78%) and Oxygen (21%).  The atmosphere has several layers.

Earth’s early atmosphere was not the same as it is today. Earth’s early atmosphere contained mostly hydrogen and helium.

These gases were replaced by gases from volcanic eruptions such as water vapor and carbon dioxide. Oxygen from photosynthetic marine organisms increased in the atmosphere and solar radiation converted some of it into ozone.

The ozone layer allowed photosynthetic organisms to emerge on land where they produced more oxygen.

The layers of the atmosphere differ in the following: 1)Temperature 2)Density 3)Amount of certain gases present 4)Pressure

The layers of the Earth are: 1)Troposphere 2)Stratosphere 3)Mesosphere 4)Thermosphere 5)Exosphere

Troposphere  Layer of the atmosphere closest to Earth (5-8 miles high)  All weather occurs in the troposphere.  Temperature decreases with height

Stratosphere  From the surface, it is the second layer of the atmosphere.  It contains the ozone layer that protects us from the UV light from the sun.  Temperature increases with height

Mesosphere  From the surface, it is the third layer of the atmosphere.  It is the coldest layer of the atmosphere.  Temperature decreases with height within this layer.

Thermosphere  From the surface, it is the fourth layer of the atmosphere.  The warmest layer of the atmosphere.  Temperature increases with height within this layer.  It contains the ionosphere.  Auroras occur here.

What is the ionosphere and why is it important? When solar energy is absorbed in the lower thermosphere and upper mesosphere, electrically charged ions are formed. The area where this occurs is called the ionosphere.

Ionosphere  Without the ionosphere, radio communication, etc. would not be possible.  It decreases at night, allowing radio waves to travel higher into the atmosphere.

Changes in Earth’s Atmosphere Man-made chemicals can deplete the ozone layer, particularly Chlorofluorocarbons (CFC’s)

The greenhouse effect keeps Earth warm. Increased levels of carbon dioxide may lead to global warming.

The Water Cycle The water cycle is the continuous movement of water from the atmosphere to Earth and back.

Inland, the primary way that water gets into the air is through transpiration.

Transpiration – The evaporation of water through pores in a plant’s leaves.

An acre of corn gives off about 3,000-4,000 gallons (11,400-15,100 liters) of water each day A large oak tree can transpire 40,000 gallons (151,000 liters) per year.

The point at which water vapor molecules start to form liquid water is the dew point. This process is called condensation.

Air contains varying amounts of water vapor. Humidity-The quantity of moisture in the air. Relative Humidity – Percent water in the air compared to what could be in the air.

Air humidity can be measured using a psychrometer.

WARM AIR  Hold more water than cold air.  Is less dense (it will rise) COLD AIR  Holds less water than warm air.  Is more dense (it will sink)

Clouds are formed when warm air rises and water vapor condenses into tiny droplets of liquid as it cools. Cloud names describe their shape and altitude.

There are three main types of clouds: cirrus, stratus, and cumulus.

CIRRUS CLOUDS  Thin and wispy  Occur at high altitudes (6-11 km. or mi. above Earth)

STRATUS CLOUDS  Sheetlike and layered.  Form at lower altitudes (about 6 km.)

CUMULUS CLOUDS  White and fluffy with somewhat flat bottoms  Form at various altitudes

Barometric Pressure – The pressure due to the weight of the atmosphere.

Barometric Pressure is also called atmospheric pressure or air pressure.

Air Pressure is measured using a barometer.

Differences in air pressure causes wind.

Earth’s rotation affects the direction of wind. Coriolis effect – The change in the direction of an object’s path due to Earth’s rotation.

Winds in the Northern hemisphere curve clockwise Winds in the Southern Hemisphere curve counterclockwise.

Global wind patterns form circulation cells.