Key Idea #14

There is a relationship between the warming of the Earth’s atmosphere by the sun and convection within the atmosphere and oceans. http://hurricanetrack.com/jpegs/ingred1.jpg

Energy from the Sun

Nuclear reactions that take place in the sun produce heat and light.

The sun is the main source of Earth’s energy, and also the major cause of heat in our atmosphere.

Most of the energy that heats up Earth’s atmosphere is from infrared radiation. The heating of the Earth at any location is related to the angle of the sun in the sky. Only a small percentage of light energy from the sun that hits the Earth produces heat energy on Earth.

Seasons FYIThe hemisphere that is tilted toward the sun receives more direct sunlight and experiences spring and summer.The hemisphere that is tilted away from the sun is receiving less direct light and experiences fall and winter.The sun’s rays are least direct at the north and south poles.

http://web.srv.cmes.utah.edu:8080/west/k12/EarthsTiltPic/view

Light energy from the sun is absorbed by the Earth’s surface and changed into heat energy. The heat energy radiates out and heats the air above.

http://www.physorg.com/news96641929.html

Carbon dioxide and water vapor in the air absorb this heat energy and radiate some of it back to the Earth’s surface, making the Earth warm enough to support life.

http://assets.panda.org/img/original/faq_1_3_fig_1.jpg

The Greenhouse Effect

Gases in the atmosphere that hold heat are called greenhouse gases. The greenhouse effect is the process by which these gases hold heat in the atmosphere. Greenhouse gases include water vapor, carbon dioxide, and methane.

Global Warming

Human activities including the burning of fossil fuels such as wood, coal, oil, and natural gas add carbon dioxide to the air. If increased carbon dioxide traps more heat, the temperature of Earth’s atmosphere increases resulting in global warming.

The Greenhouse Effect and Global Warming

Heat refers to the energy transferred from a hotter object to a cooler one.

Heat is transferred in three ways:radiationconductionconvection

Radiation, conduction, and convection in a lava lamp.

Radiation The light bulb on a lava lamp heats coil.

ConductionThe heated coil touches “lava” causing molecules to speed up and spread out.

ConvectionThe warm lava rises because it is less dense (D=M/V).The “lava” that is further from the energy source cools causing molecules to move closer together. The cooled “lava” sinks because it is more dense.

Radiation, conduction, and convection work together to heat the troposphere.

Radiation: The direct transfer of energy from the sun by electromagnetic waves and is felt as heat.

ConductionThe direct transfer of heat energy caused by contact between one object and another (example: your feet on hot sand).

Convection

The transfer of heat energy through fluids (liquids and

gases) by moving particles.

http://www.kudzuacres.com/wwow/lessons/weather/radiationconduction.gif

Convection currents move warm air through the atmosphere.

Convection takes place because cold air is more dense than warm air. Cold, dense air sinks which forces the warm, less dense air to rise. Convection currents causes most of the heating of the troposphere.

http://www.propertiesofmatter.si.edu/images/L5/conv_cell_atmos_labeled.gif

The Sun and Weather