The atmosphere is to the earth what the skin of an apple is to the apple. What does this mean?
Weather <ul><li>Four variables interact to cause weather. They are: </li></ul><ul><li>Heat </li></ul><ul><li>Air pressure </li></ul><ul><li>Wind </li></ul><ul><li>Moisture </li></ul>
Where do you think the heat comes from that makes our weather change? Of course, the sun!
Three forms of the sun’s energy come through the atmosphere and have an effect on our atmosphere and weather. They are: Visible light Ultraviolet radiation Infrared radiation
Energy comes to us from the sun in the form of electromagnetic waves. (We will study more about this when we study stars.)
Ultraviolet radiation The sun emits different wavelengths of ultraviolet radiation. UVA, UVB, and UVC. UVB and C are very bad for living things. Most is absorbed by the ozone layer in the stratosphere. Ozone is our protector! UV is what makes us sunburn and causes most skin cancer. http://www.uvdi.com
Infrared (IR) radiation is the scientific name for heat energy. The sun is not the only thing the gives off IR. Infrared This is an infrared image of a jeep with its engine running. White is hottest! http://www.atc.army.mil/
What happens to the sun’s energy when it reaches our atmosphere? Notice that this diagram is similar to the one in your book on page 454.
Heat always moves from a higher temperature place to a lower temperature place so the energy gets transferred (moved). What happens to the heat energy when it reaches the Earth’s surface?
The scientific name for heat energy is THERMAL ENERGY. We use two common scales Metric uses Celsius USA uses Fahrenheit (Both named after the scientist that came up with the measurements.) 0 degrees C 32 degrees F 100 degrees C 212 degrees F
Heat is transferred in three ways: 1. Radiation 2. Conduction 3. Convection
Radiation Requires no substance to travel from one place to another. It can move through the vacuum of space . Energy from the sun comes to us through radiation. Video about radiation
Conduction http://cache.eb.com/ Heat is transferred from atoms that are touching . It is not carried by a liquid or gas. Example: You walk on a hot sidewalk barefooted and your feet get hot. The heat is moving from the atoms of the sidewalk to your feet. Video segment on conduction
The layer of air above the earth is warmed by conduction (the transfer of heat by contact) molecule by molecule from the hot earth to the layer of air touching the sand. The heat is also conducted to your feet when you walk on the beach.
Convection Video about convection Convection occurs when heat is transferred through a liquid or a gas. The heat is carried from one place to another by a convection current .
Heat warms the atmosphere best when it is in the form of convection currents . Convection currents form when heated air expands, becomes lighter, and rises. The heat is carried upward. This is convection! It also happens with liquids.
Without an atmosphere, the sky would be black like the moon's sky. As light goes through an atmosphere, it gets scattered. This scattered light is what “lights up” the sky. This picture was taken by Apollo astronauts from the surface of the moon. Notice that the ground has light, so it is daytime on the moon where the picture was being taken.
The Greenhouse Effect – The process whereby energy gets absorbed by the gases in the atmosphere warming the earth.
Atmospheric gases act like the glass of a greenhouse and trap heat close to the earth. Video segment on the greenhouse effect http://generalhorticulture.tamu.edu
Carbon dioxide is one of the major greenhouse gases. The carbon dioxide molecules absorb infrared radiation (heat) and the molecule starts to vibrate. This means it heats up and can transfer that heat to other atoms in the atmosphere.
This means that even though the North Pole could have six months of daylight, the energy is so spread out that it does not provide much heat in an area. Look at the color of the light hitting the earth and how spread out the energy is. It’s like spreading the same amount of peanut butter on bigger and bigger pieces of bread!
Not only does energy change due to latitude, it can vary based on the time of year. What does this diagram show?
Can you answer these questions? <ul><li>Where does the energy come from that drives our weather? </li></ul><ul><li>Which type of radiation is also known as heat? </li></ul><ul><li>Why is it good that most UV radiation is blocked by our atmosphere? </li></ul><ul><li>How is thermal energy measured? </li></ul><ul><li>What is the difference between conduction, convection, and radiation? </li></ul><ul><li>What is the greenhouse effect? </li></ul><ul><li>What gas seems to have the most effect on our atmosphere? </li></ul><ul><li>Why does your location on Earth make a difference in how much heat you get from the sun? </li></ul><ul><li>Do you have any questions? </li></ul>