|Earth and Space Science||Structure of the Earth 7I5.00||Process of Science||Collecting Data 1.3 b|
Sponsored by the National Science Foundation
CONTENT STANDARD: Earth and Space Science
CONTENT TOPIC: Structure of the Earth
CONCEPT: The earth's weather is an interaction of many parts of the environment.
CONTENT OBJECTIVE: 7I5.00 To understand factors affecting the earth's weather
INSTRUCTIONAL OBJECTIVES: The learner will:
TN COMPONENT OF SCIENCE: Process of Science
BENCHMARK: Information may be acquired from a variety of sources such as reference books, computer disks and databases, and back issues of periodicals.
The earth is a spinning sphere, the equator of which is just a few degrees away from being parallel with the plane of the earth's orbit around the sun. This means that the intensity of irradiance per unit area is always less at high latitudes than it is at the equator. Low latitudes, therefore, get more heat, this being the primary inequality in energy supply that imposes a patchwork of climates on the earth. The height above sea level of a place also helps determine the climate. The higher one goes above seal level, the lower the average yearly temperature will be. There is, as we know, snow all year long on the tops of many high mountains, even at the equator. (Use map/glove as reference here.)
Most of the energy of sunlight penetrates the atmosphere and strikes the surface of the solid or liquid earth, where the wavelengths of light are absorbed and re-emitted as radiant heat. The primary heating of the atmosphere, therefore, is from below, from the ground and ocean surfaces. The warmed air rises; as it rises it expands; as it expands it cools. Column of rising air as it expands is the reason mountain tops are cold. Energy to do this work can come only from the air itself and it loses temperature accordingly. (Use map/globe as reference here.)
The major wind systems of the earth result from the fact that large masses of air around the earth's equator are forced to rise by bottom heating, causing air to rush in from high latitudes to fill the void. Winds represent the working of a heat-distributing engine. Heat is applied at the equator, the air moves up and then pole ward, descends and returns equator ward along the earth's surface. This system is modified by properties of scale and by Coriolis force which is the force that diverts the air through it own momentum. Coriolis force deflects moving air or water to the right in the northern hemisphere and to the left in the southern hemisphere.
Mountains and hills cause air masses that move toward them to rise. As an air mass rises and cools, water vapor condenses and falls to the earth. If the prevailing wind comes from the west, the rain will fall on the west side of the mountains. This side of the mountain will get enough moisture so that crops may be grown. On the east side of the mountain, however, the climate will be dry. The result is termed a mountain rain shadow. The Atacama Desert is a classic example of a mountain shadow desert. This desert is located on the coast of Chile. Since the winds come from the east, the result is that the western side of the mountain is very dry, resulting in a desert biome. The Atacama Desert is found on the edge of the ocean! Large bodies of water affect the climate, too.
Large bodies of water have a moderating effect on temperature. That is, if it is cold inland, the land near the large body of water will not be as cold as it is inland. If it is hot inland, the land near the water will not be as hot. So the climate is usually milder near the water. Inland, however, there my be great differences between the coldest and warmest temperatures.
Ocean currents play an important part in determining the climate, too. The Gulf Stream moves from the warm Caribbean area, along the eat coast of the United States, to about Cape Hatteras. Then most of it moves across the Atlantic to Europe, Northern Europe would have a colder climate than it has if this warm current did not reach its coasts.
(Students should be expected to research these topics as a group and to present their findings orally. An ecology text will be indispensable at this point and should be made available for them; however, most of the research could and should be done in the school library. All of these terms are essential vocabulary words which each student will need a working knowledge of in order to comprehend and appreciate this unit.)
2. Make a barometer with two jars. Fill a tall, wide-mouthed jar about half full of water. Fill an olive jar about one fourth full of water. Seal the olive jar with a stopper. Invert the olive jar into the wide-mouthed jar. The olive jar should be able to float freely in the wide-mouthed jar. Remove or add water to the jars so that the water levels in both jars will be equal when the narrow jar floats in the wide-mouthed jar. The barometer is now ready to use. Observe it twice a day. If the air pressure is rising, the water level in the narrow jar will be higher than in the wide-mouthed jar. If the air pressure is falling, the water level in the wide-mouthed jar will be higher. Discuss the significance of high and/or low pressure and the resulting weather.
3. Place a lamp, to represents the sun, on a table or have someone hold the lamp in the middle of a room. Turn it on and darken the room Hold a globe away from the lamp but close enough so that the lamp illuminates part of the globe and other part is left in a shadow. Without changing the direction that the glove is facing or the angle of the globe's axis, move the globe in an orbit around the lamp. Note the position of the United States at the start of the orbit, at one-quarter orbit, at one-half orbit, at three-quarters orbit, and at full orbit. The start position and the full orbit position should be exactly the same. Repeat the orbit while rotating the glove on its axis.
a. At what point in the earth's orbit is the United States receiving the sun's rays most directly? (response) At what season of the year does this occur? (response)
b. What season of the year in the United States would correspond to the northern half of the earth's being tilted toward the sun? (response)
c. What season of the year would correspond to the northern half of the earth's being tilted away from the sun? (response)
d. In what seasons of the year would the axis of the earth not be tilted either toward the sun or away from it? (response)
3. How is weather affected by these factors? (response)
4. In order to show that warm air rises, take the top off a shoe box. Turn the box on its side. Cut two holes in the upper side of the box so that a cardboard tube can fit snugly in each hole. Place a cardboard tube in each hole so that it stands up straight but does not extend into the box very far. If necessary, tape the tubes to the box so that they do not slide down in the holes.
Place a small, lighted candle in the box below one of the holes that contain a cardboard tube. Coat one end of a stiff piece of cloth with petroleum jelly and light the end that has the jelly on it so that the cloth produces some smoke. Hold the cloth above the cardboard tubes about midway between them. Note what happens to the smoke. Now hold the cloth nearer the tube that the smoke does not go down to see if it will go down that tube. Remove the smoking cloth and hold a thermometer above each tube for two minutes. Record the temperature of each place.
On your paper, briefly describe the birth of a storm in the Atlantic Ocean which could effect the East Coast drastically and our region of the country as well. Include factors you have learned this week which are responsible for these changes
biome - an ecosystem of a large geographic area in which plants are of one formation and for which climate sets the limits.
Coriolis force - force which diverts air and water through its own momentum
environmental variables - temperature, precipitation, wind, and air pressure
Gulf Stream - current which carries warm tropical water up the East Coast
mountain rain shadow - located on opposite side of mountain from prevailing winds which, because the air has warmed and holds more water, results in dry conditions
This is the time this file has been accessed since 04/02/98.
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