the Atmosphere’s Role in Weather

What is the Atmosphere? The atmosphere is a mixture of gases that surround the Earth The atmosphere is made up of 78% nitrogen, 21%oxygen and 1% argon, CO2, water vapor and other gases The atmosphere is mostly gas, but contains small amounts of solids and liquids Solid particles like Dust, ash, dirt, smoke Liquid water in droplets in clouds

Atmospheric Pressure Air pressure is the measure of the force with which the air molecules push on a surface Gravity is what holds the Earth’s atmosphere in place Air pressure changes throughout the atmosphere As Altitude increases, air pressure decreases Air pressure is greater near Earth’s surface

Layers of the atmosphere Troposphere – Lowest layer/closest to Earth Where we live - Densest layer – where weather happens Stratosphere – 2nd layer Thin air - cold - contains the ozone layer(absorbs solar energy and UV radiation) Mesosphere – 3rd Layer Coldest layer Thermosphere – Uppermost layer High temperature caused by fast moving particles that rarely touch one another

Heating the Atmosphere - Radiation The Earth receives energy from the sun by radiation Radiation is the transfer of energy in electromagnetic waves The sun’s radiation is absorbed, causes molecules to speed up and increase temperature This can happen to your skin as well as the surface of the Earth

Heating the Atmosphere – Conduction Conduction is the transfer of thermal energy from one material to another by direct contact Always moves from warm to cold (ex. Your foot on a hot sidewalk) When air molecules come in contact with a warm surface thermal energy is transferred to the atmosphere

Heating the Atmosphere – Convection Most Thermal energy in the atmosphere moves by convection When air is heated it becomes less dense and rises – cool air is more dense and sinks The continual process of warm air rising and cool air sinking creates a circular movement of air called a convection current

The Greenhouse Effect The process where the gases(such as CO2) in the atmosphere trap thermal energy Global warming is due to an increased amount of thermal energy being trapped by “greenhouse gases” in the atmosphere A radiation balance needs to be maintained in order for the Earth to be “livable” Balance between incoming radiation and outgoing energy