18.1

 Made up of mainly two gases: – Nitrogen 78% – Oxygen 21% – Trace Gases 1%

 made up of 5 layers: – Troposphere – Stratosphere – Mesosphere – Ionosphere – Thermosphere

 The atmospheric layer we live in.  Almost all weather occurs here.  Contains water vapor and oxygen.  Highest density  Temps decrease as you increase altitude until you reach the top of the layer called the tropopause.

 Within the troposphere a temperature inversion may occur.  This is a condition where warmer air traps cooler air near the Earth’s surface.  This can cause air to get thick with pollution, where it can’t escape.

– Lacks O 2 and water vapor. (no weather) – Contains the ozone (O 3 ) layer. (this layer absorbs solar UV radiation) – Temperatures increase as you gain altitude. – Higher altitude than most aircraft would fly

– The coldest of layer of the atmosphere. (-80 0 C) – Temperature decreases with altitude

 Consists of upper mesosphere and lower thermosphere.  Contains charged ions that reflect radio waves allowing transmissions to travel great distances.  Radio waves will travel farther at night than during the day. (less ions)  Where the aurora borealis can be seen. (excited photons)

 Most outer layer.  Hottest layer (980 0 C)  temperatures will increase with increase altitude  It absorbs solar radiation

 Early atmosphere was much different during Earth’s early days.  Volcanic eruptions released H 2, ammonia, methane. CO, CO 2 and N 2.  No oxygen was present

 Around 2.5 billion years ago single celled organisms evolved to capture the suns energy and CO 2 to start the photosynthesis process  Then plants began appearing releasing oxygen into the atmosphere.

 350 million years later aerobic organisms came along and balanced the atmosphere.  They took in oxygen and released carbon dioxide as a by product during respiration.  And thus the O 2 and CO 2 cycle was created.

 Protects us from UV radiation.  Can be destroyed by chlorofluorocarbons or CFC’s  Used during 1950s thru 1980s in refrigerators and spray cans.  CFCs are now banned in most countries  Ozone layer is repairing itself

 Ozone while helpful in stratosphere, is very toxic if trapped in the troposphere.  Main gas pollutant from cars, trucks, factories that causes smog.

 The process by which the atmosphere traps some of the energy from the sun in the troposphere.  CO 2, water vapor, and other gases absorb the suns energy (greenhouse gases)  Keeps the planets climate balanced

 We are adding more and more CO 2 and other greenhouse gases into the atmosphere: – Forest fires and volcanoes – Air Pollution from fossil fuel burning – Increasing human population – Decrease in plant life and rain forest – Increase of cattle grazing

18.2

 The continuous movement of water from atmosphere to Earth and back.  4 mechanisms of travel

 Water enters the atmosphere: 1. Evaporation  Evaporation occurs at the lakes, rivers, and oceans. 2. Transpiration  evaporation of water through plant’s leaves.

Water Exits: 3. Condensation  Water vapor rises until it is cool enough to condense to form clouds. 4. Precipitation  When the cloud become full of water droplets they will release moisture back down to Earth in the form of rain, sleet, ice, or snow.

Condensation Evaporation

 Water vapor is always in the air  Humidity – The quantity/amount of water vapor in the atmosphere  Relative humidity (percentage) – is the actual amount of water in the atmosphere compared to maximum amount it can hold.  The higher the temperature, the more water that can be held in the air.

 The temperature at which water vapor molecules start to form liquid water.  Higher the humidity the higher the dew point.  dew point dew point

 Made up of tiny condensed droplets of liquid water.  3 main types

 highest altitude clouds  appear wispy and light.

 layered or sheet like clouds  form at lower altitudes.

 white and fluffy  appear at many levels.

 Other clouds are a combination of the 3 cloud types.  The root nimbus means the cloud contains precipitation. (grayer color)  Ex. cumulonimbus produce thunderstorms

 The pressure due to the weight of the atmosphere.  Measured with an instrument called a barometer.  Air pressure decreases with altitude in the troposphere

 Caused by differences in air pressure between air masses.  The greater the difference the stronger the wind.  Air always flows from high pressure to low pressure – Pressure inside a plane is greater, so air would be sucked out if a window broke

 Coriolis effect. the change in direction of an object’s path due to Earth’s rotation.

 Winds in the Northern hemisphere curve right.  Winds in the southern hemisphere curve left.

18.3

 The condition of the atmosphere at any given time  Weather is caused by traveling air masses. – Large bodies of air with the same general characteristics throughout.

 A boundary where two air masses with different densities meet.  Fronts cause precipitation, change in temperature, and a change in wind direction.

 Warm front -warm air moves over cooler air forming clouds. -Produces steady rain or snow for a couple of days. Cirrus and cirrostratus clouds

 Cold fronts -Cold air moves under slow moving warm air -Brings high winds, thunderstorms, and possible tornadoes. Cumulonimbus clouds

 Two air masses meet  Neither is displaced  Air masses move side by side  Similar to warm front weather

 Lightening is caused by a build up of electrical charges from water droplets and ice crystals in clouds.  When opposite charges are found on the ground or other clouds, lightening strikes.  Thunder is the sound of lightening.

 If you count to 10 or less after seeing lightning before hearing thunder, then the storm is less than two miles away.

 Form during severe thunderstorms.  Form from cool air from the north, and warm air from south.  Tornadoes begin as a funnel cloud that intensifies until it touches ground  Most violent winds on Earth 310mi/hr  Most common in the Midwest

 Very large storms with high winds.  Also known as cyclones and typhoons  Form in the tropics  Created by rising warm water vapor from warm ocean water.  Then powered by the energy released from water vapor condensing into clouds

 Produced by meteorologists to help forecast weather.  They use many variables – Precipitation and cloud cover – Wind speed -Air pressure (isobars) – fronts

 Average weather condition over many years for a particular region.  It is not measured day by day.

1. Latitude (closeness to equator)  Angle at which the sun hits Earth 2. Cycling of seasons and season Length  The tilt of the earth’s axis as it travels a revolution around the sun is the reason that we have seasons. 3. Yearly rainfall 4. Topography (type of land)  Elevation, amount of water, mountains or flatness