OUR ATMOSPHERE The thin layer of gases that surrounds our planet and is held in place by gravity.

Composition A mixture of Changes according to altitude and location. Gases Dust Water vapor Changes according to altitude and location.

Ozone (O3) – a very rare type of molecule that combines 3 atoms of oxygen Thin layer is found in the Stratosphere Protects living things from harmful UV sun rays Man made chemicals destroy ozone.

Carbon Dioxide (CO2) A naturally occurring gas in our atmosphere. Needed for photosynthesis to occur during the Carbon Cycle. Produced as waste during cellular respiration.

Water Vapor - water in the atmosphere The key to understanding atmosphere processes The source of all precipitation Examples Clouds Fog Rain Snow Sleet Hail

Changing states of matter Changing matter requires energy, and is transferred in the form of heat Latent heat – heat that is used which doesn’t cause temperature change

How does water change state in the atmosphere?

The Greenhouse Effect

The atmosphere is divided into 4 main layers by temperature Troposphere (bottom layer) Stratosphere (where important weather occur) Mesosphere Thermosphere (top layer) It generally gets colder as altitude increases Layers of the atmosphere are divided by temperature and height

Layers of the atmosphere

Earth-Sun Relationship Almost all energy that causes Earth’s weather and climate comes from the sun. Unequal heating of the Earth causes weather.

Heat transfer Conduction – transfer of heat via molecular activity (high to low) Convection – transfer of heat by movement or circulation within a fluid Radiation – transfer of heat in all directions

Solar radiation Energy is absorbed by the object. Energy is transmitted Energy is reflected or bounced off the object.

Humidity – the amount of water vapor in the air Relative humidity – the amount of water in the atmosphere. A percentage of how much water the air can hold.

Cloud Formation As air rises in the atmosphere it expands and cools When air reaches it’s dew point, clouds begin to form

Air compression When air pressure increases, air temperature rises Motion of the gas molecules increases When air pressure decreases, air expands and temperature cools Motion of the gas molecules slows

Orographic Lifting when air is forced to rise and cool due to terrain features such as hills or mountains

Frontal Wedging When cold dense air acts as a barrier and causes warmer, less dense air to rise

Convergence When air masses flow together from more than 1 direction, air rises. Low pressure is the result

Localized convective heating Unequal heating of Earth’s surface causes pockets of air to be warmed more than surrounding air Causes pockets of air to rise, forming thermals

Clouds – 3 basic types are classified on form and height Cirrus Cumulus Stratus

High Clouds cirrus cirrostratus cirrocumulus Thin and white Low precipitation May warn of approaching stormy weather cirrocumulus

Middle Clouds - alto altocumulus Altocumulus – large and dense Altostratus – white or gray sheet covering sky Cumulonimbus - Infrequent light snow or drizzle altocumulus

Low clouds Stratocumulus Stratus – fog like layer covering sky - Occasionally produce light precipitation Stratocumulus – rainy clouds Nimbostratus – main precipitation maker Cumulus - clouds with vertical development Stratocumulus

Fog – cloud with base at or near the ground Form by Cooling – air over a cold surface Evaporation – when cool air moves over warm water (steaming)

How precipitation forms Tiny cloud droplets grow in volume by about 1,000,000 times.

Cold cloud precipitation Ice crystals contact with cloud droplets causing them to freeze Causes ice to grow into snowflakes Rain often begins as snow high in the clouds

Warm cloud precipitation Large droplets moving through the clouds collide and join (coalesce) with smaller droplets

The type of precipitation that reaches Earth’s surface depends on temperature in the lower atmosphere Rain Snow Sleet Glaze Hail

Atmosphere key ideas Earth’s atmosphere is made up of a combination of gases. The major components of nitrogen, oxygen, and argon remain constant over time and space, while trace components like CO2 and water vapor vary considerably over both space and time. The atmosphere is divided into the thermosphere, mesosphere, stratosphere and troposphere boundaries between these layers are defined by changes in temperature and height Pressure decreases exponentially with altitude in the atmosphere. Our knowledge about the atmosphere has developed based on data from a variety of sources, including direct measurements from balloons and aircraft as well as remote measurements from satellites.