Air & The Atmosphere What is the atmosphere? Slide 1 – 10 DAY 1 How high does the atmosphere go activity, apply picture (Assignment #1)

What is the atmosphere? The Earth is surrounded by a blanket of air, which we call the atmosphere. It reaches over 560 km from the surface of the Earth It moderates temperature, protects us from harmful radiation and supports life.

The 1st Billion Years The atmosphere was formed by outgassing of the Earth The composition of the primitive atmosphere: carbon dioxide nitrogen water vapor There was originally no oxygen it formed later as a result of photosynthesis

Composition of the Atmosphere Contemporary Atmosphere: Nitrogen 78.09% Oxygen 20.95% Argon 0.93% Carbon Dioxide 0.03% less than 0,01% Neon Helium Methane Krypton Hydrogen Nitrogen Suboxide Xenon Ozone

Troposphere The lowest layer of Earth’s atmosphere Reaches a height of 7 to 20km above sea level Almost all weather occurs in this layer The temperature generally decreases as altitude increases

Stratosphere Located above the troposphere and below the mesosphere The earth's ozone layer is located in the stratosphere. Ozone, a form of oxygen, is crucial to our survival; this layer absorbs a lot of ultraviolet solar energy. Temperatures rise as one moves upward through the stratosphere

Mesosphere Located above the stratosphere and reaches up to 85 km above Earth's surface Temperatures drop with increasing altitude to about - 100°C – this is the coldest part of the atmosphere The layer in which a lot of meteors burn up while entering the Earth's atmosphere. From the Earth they are seen as shooting stars.

Thermosphere Located directly above the mesosphere and below the exosphere (1000 km above sea level) Temperature increases with altitude getting as high as 1727 degrees Celsius (due to the Suns energy) Much of the X-ray and UV radiation from the Sun is absorbed in this layer

Exosphere The outermost layer of the Earth's atmosphere The lower boundary of the exosphere is called the critical level of escape, where atmospheric pressure is very low (the gas atoms are very widely spaced) and the temperature is very low In this region atoms and molecules escape into space

Heat Transfer Within the Atmosphere Nearly all energy in the Earth’s atmosphere comes from the sun. Energy travels to the Earth in the form of electromagnetic waves. Most of the energy from the sun reaches the Earth in the form of visible light and infrared radiation, and a small amount of ultraviolet radiation. Slides 11 – 14 DAY 2 – Goldilocks activity (assignment #2)

UV Radiation Clouds reflect radiation back into space Dust and other gases scatter radiation in all directions The Earth’s surface absorbs radiation, and reradiates it as longer wave infrared (heat)

Greenhouse Effect The greenhouse effect is a naturally occurring process that aids in heating the Earth's surface and atmosphere Results from the fact that certain atmospheric gases, such as carbon dioxide, water vapor, and methane, are able to change the energy balance of the planet by absorbing long wave radiation emitted from the Earth's surface Without the greenhouse effect life on this planet would probably not exist as the average temperature of the Earth would be a chilly -18° Celsius, rather than the present 15° Celsius

Greenhouse Effect

Heat Transfer The science of how heat flows is called heat transfer Heat flow depends on the temperature difference Two bodies are in thermal equilibrium with each other when they have the same temperature In nature heat always flows from hot to cold until thermal equilibrium is reached

Three Methods of Heat Transfer Conduction: transfer of heat through matter by molecular activity Convection: is the transfer of heat by movement of heated material (usually in liquids and gases) Radiation: transfer of heat through wave energy Slides 15-25 DAY 3 – picture activity and Radiation Lab

Conduction Good and Poor Conductors Air is a poor conductor, thus most energy transfer by conduction occurs right at the earth's surface. At night, the ground cools and the cold ground conducts heat away from the adjacent air. During the day, solar radiation heats the ground, which heats the air next to it by conduction.

Convection In the atmosphere, convection includes large- and small-scale rising and sinking of air masses and smaller air parcels. These vertical motions effectively distribute heat and moisture throughout the atmospheric column. Sea Breeze and Land Breeze? and contribute to cloud and storm development (where rising motion occurs) and dissipation (where sinking motion occurs).

Radiation Radiation is heat transfer by electromagnetic waves Thermal radiation is electromagnetic waves produced by objects because of their temperature We do not see the thermal radiation because it occurs at infrared wavelengths invisible to the human eye