Unequal Heating, Air Pressure and Winds

What causes air pressure? It is caused by the uneven heating of the Earth's surface by the sun. Because the Earth's surface is made of very different types of land and water, it absorbs the sun's heat at different rates.

Air Pressure Review Air is matter! Air has mass. Air takes up space. Air has density. Air pressure is the weight of a column of air pressing down on an area.

Atmosphere/Pressure Atmosphere held in place by gravity Pressure strongest at surface-more air above you *as altitude increases, air pressure decreases Stack of books

Air Pressure As Air Pressure decreases, so does density.

Atmosphere Atmosphere: a mixture of gases that surrounds Earth: acts like a blanket Contains oxygen Protects from sun

Layers of the Atmosphere Troposphere: all weather happens here Stratosphere: ozone layer-protects us Mesosphere: middle layer Thermosphere: hottest layer

Atmosphere

Composition of Troposphere Nitrogen=78% Oxygen=21% Other 1%=water vapor, CO2 and other

Weather Factors Sun’s energy travels to earth as Electromagnetic waves. What type of heat transfer is this?

Weather Factors Scattering: Reflections of light in all directions. Why is the sky blue?

Radiation Ever feel the heat of the sun on your face or the heat from standing by a campfire? That is radiation. It is the direct transfer of energy by electromagnetic waves through space.

Conduction Have you walked barefoot on the sand at the beach and the sand burned your feet? That is conduction. It is the direct transfer of heat from one substance to another through direct contact.

Convection Did you come in after the snow with wet shoes on and your mother told you to put them over the heating vent to dry? How does this dry them even though the actual furnace is in the attic? That is convection. The transfer of heat by the movement of fluid or air. Hot air rises, cold air sinks.

How is Earth heated? Light/heat from the sun RADIATES through the atmosphere, hits the Earth where it is absorbed. This heats the air above it by CONDUCTION. This heat rises up to the greenhouse gases where it is trapped, cools, sinks and heats at the surface again.-CONVECTION.

Weather Factors

Greenhouse Effect These gases absorb the heat and act as a “blanket” to keep Earth warm. Some greenhouse gases: water, methane, carbon dioxide.

Hot Air Rises… But how does the ground get hotter Hot Air Rises… But how does the ground get hotter??? … It is farther from the sun! Air in the atmosphere acts as a fluid (water vapor). The sun's radiation strikes the ground = warming the rocks/ground. As the ground’s temperature rises due to conduction, heat energy is released into the atmosphere, forming a “bubble” of air which is warmer than the surrounding air. This “bubble” of air rises into the atmosphere. As it rises, the air in the “bubble” cools and becomes more dense. The movement of the air creates wind. Convection currents are responsible for many weather patterns in the troposphere.

Convection Currents!