Introduction to the Atmosphere The air around us.

What is the atmosphere? The Earth is surrounded by a blanket of air, which we call the atmosphere. It reaches over 560 kilometers (348 miles) from the surface of the Earth, so we are only able to see what occurs fairly close to the ground. This “blanket” moderates temperature, protects us from harmful radiation and supports life.

Composition of the Atmosphere The present composition of the atmosphere is: 21% OXYGEN (O2) 78% NITROGEN (N2) 0.04% CARBON DIOXIDE (CO2) ~0.9% ARGON (Ar) Besides water vapor, several other gases are also present in much smaller amounts: Carbon monoxide (formula CO) Neon (Ne) Oxides of nitrogen Methane (CH4) Krypton (Kr)

THE FIRST BILLION YEARS The Earth's surface was originally molten, as it cooled the volcanoes out gassed out massive amounts of: CARBON DIOXIDE, STEAM (H2O vapor), AMMONIA and METHANE. There was NO OXYGEN. The STEAM condensed to form water which then produced shallow seas.

Layers of the Atmosphere

The Troposphere Troposphere: The troposphere is the lowest region in the Earth's (or any planet's) atmosphere. On the Earth, it goes from ground (or water) level up to about 11 miles (17 kilometers) high. Weather and clouds occur in the troposphere. In the troposphere, the temperature generally decreases as altitude increases.

The Stratosphere The stratosphere : 11 and 31 miles (17 to 50 kilometers) above the earth's surface. 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 so temperature increases Only the highest clouds (cirrus, cirrostratus, and cirrocumulus) are in the lower stratosphere.

The Troposphere vs. the Stratosphere

The Mesosphere The mesosphere : 31 and 50 miles (17 to 80 kilometers) above the earth's surface Temperatures in the mesosphere drop with increasing altitude because there is no concentrated ozone layer here In the mesosphere temperatures that quickly decrease as height increases. The mesosphere is also 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.

The Thermosphere Temperature increases with altitude due to the Suns energy. Temperatures in this region can go as high as 1,727 degrees Celsius. Air particles are so widely spaced though that it doesn’t feel this hot going through the layer Radiation causes the scattered air particles in this layer to become electrically charged (see ionosphere), enabling radio waves to bounce off and be received beyond the horizon.

The Ionosphere The thermosphere can be identified in two parts- the ionosphere and the exosphere. Ionosphere: 70 km-640 (about 400 miles = 640 km). It contains many ions and free electrons (plasma). Auroras occur in the ionosphere. The Aurora , or northern lights are a result of particles from the sun coming into contact with the Earth’s atmosphere.

The Exosphere Exosphere: the outermost layer of the Earth's atmosphere. From about 400 miles (640 km) high to about 800 miles (1,280 km). The lower boundary of the exosphere is called the critical level of escape, where atmospheric pressure is very low (the gas atoms Hydrogen and Helium are very widely spaced) In this region, atoms and molecules escape into space.

Types of Heat Transfer Three types of heat transfer: (1) Conduction (2) Convection (3) Radiation

Conduction Convection Radiation

Conduction Conduction is the flow of heat from one object to another by direct contact between the two objects   Ex: The electric heating coil of a stove transfers heat to a metal pan by conduction

Conduction Some solids, such as metals, are good conductors of heat while others, such as wood, are poor conductors. Air and water are relatively poor conductors. Since air is a poor conductor, most energy transfer by conduction occurs right at the earth's surface.

Conductor Insulator

Convection Convection is the flow of thermal energy that occurs when a warm liquid or gas moves from one place to another. Think Convection Currents!

Convection Convection also requires physical contact. It takes place because of the difference in density in fluids as they are heated and cooled. Liquids or gases that are heated become less dense and rise. As they cool, they become more dense and fall. This cycle of movement is called a convection current.

Radiation Radiation is a transfer of thermal energy that does not require contact or a medium such as a gas or liquid. EX: The sun transfers energy through the vacuum of space by radiation.

Quick Quiz!

Conduction

Radiation

Convection

Conduction

Convection

Radiation

Conduction