Describe how air pressure is exerted on objects. Explain how changes in air pressure affect the mercury column of the barometer. Identify the ultimate energy source for wind. Describe how the Coriolis effect influences freely moving objects.
Using vocabulary sheet write the terms and what you think they mean. Later after the lesson you will write the scientific definition.
Air pressure Barometer Pressure gradient Coriolis effect Jet stream
1. Describe how air pressure is exerted on objects. 2. What happens to the mercury column of a barometer when air pressure changes? 3. What is the ultimate energy source for wind? 4. How does the Coriolis effect influence free-moving objects?
TopicMain Ideas Air Pressure DefinedAir pressure is… Measuring Air Pressure Factors Affecting Wind
Purpose – Students prove air has mass by comparing the mass of a balloon when empty and when filled. Materials – balloon, balance Procedure – Blow up a balloon and determine its mass using a balance. Remove the balloon, release the air, and replace the balloon on the balance. Find the mass again. Expected Outcomes – Students will see that they empty balloon is lighter than the air filled balloon.
Materials Clear cup, cork, beaker, tray Procedure Try to push a cork to the bottom of the water using only an upside-down cup. Draw a sketch of the result on page 2. How does this prove that air takes up space? Scientist define matter as anything that has mass, and takes up space
Air pressure is simply the pressure exerted by the weight of air above. Average air pressure at sea level is about 1 kg per square centimeter. Roughly the same pressure as a column of water 10 meters in height. Air pressure is exerted in all directions – down, up, and sideways. The air pressure pushing down on an object balances the air pressure pushing up on the object.
Average air pressure at sea level is about 1 kilogram per square centimeter.
Meteorologists measure atmospheric pressure with a unit of millibars. Standard sea level pressure is 1013.2 millibars. A barometer is used for measuring air pressure. Bar = pressure Metron = measuring instrument.
Described the atmosphere as a vast ocean of air that exerts pressure on us and all objects around us. To measure the force, he filled a glass tube, closed at one end, with mercury. Then he put the tube upside down into a dish of mercury.
When air pressure increases, the mercury in the tube rises. When air pressure decreases, so does the height of the mercury column. Improvements from Torricelli’s barometer have been made but, the barometer is still used for measuring air pressure.
Aneroid barometer is smaller and more portable It uses a metal chamber with some air removed. One advantage of the aneroid barometer is that it can be easily connected to a recording device. Provides continuous record of pressure changes with the passage of time.
Purpose – students show that air pressure is exerted in all directions - down, up, and sideways. Materials – glass, water, cardboard, sink Procedure – Fill the glass with water to the brim. Place a piece of cardboard on top of the glass. Working over a sink, hold the cardboard in place and invert the glass. Then, remove your hand from the cardboard. Expected Outcomes – The pressure of the air pushing up on the cardboard holds it against the full glass of water, preventing it from spilling.
Wind is the result of horizontal differences in air pressure. Air flows from areas of higher pressure to areas of low pressure. The unequal heating of Earth’s surface generates pressure differences. Solar radiation is the ultimate energy source for most wind.
If Earth did not rotate, and if there were no friction between moving air on Earth’s surface, air would not flow in a straight line from areas of higher pressure to areas of lower pressure. Three factors combine to control wind: 1. Pressure differences 2. The Coriolis Effect 3. Friction
Wind is created by differences in pressure – the greater the pressure the greater the differences are, the greater the wind speed. Air pressure is determined by using barometers. The data are shown on maps using isobars.
Isobars are lines on a map that connect places of equal air pressure. The spacing of isobars indicates the amount of pressure change occurring over a given distance. These pressure changes are expressed as the pressure gradient.
Closely spaced isobars indicate a steep pressure gradient and high winds. Widely spaced isobars indicate a weak pressure gradient and light winds. The pressure gradient is the driving force of wind. It has both magnitude and direction. Its magnitude is reflected in the spacing of isobars. The direction of force is always from areas of high pressure to areas of low pressure and at right angles to the isobars.
For this particular map, isobar lines are most closely spaced in the low-pressure cell, which indicates fastest wind speeds in this cell.
TopicMain Ideas Air Pressure DefinedAir pressure is the weight of air above. It is exerted in all directions. Measuring Air PressureAir pressure is measured with barometers, using the principles that fluids will deform if the weight of the air is exerted on them. Factors Affecting WindThe pressure gradient, Coriolis effect, and friction
By William Kamkwamba and Bryan Mealer AR Book read aloud
On page 8 you will need to answer the following questions in complete sentences. Will be posted during the reading.
1. What did William wonder as a truck rumbled past the fields where he worked? 2. What did William’s father tell his family after the rain had stopped? 3. When did William decide to build electric wind? 4. What happened right before William shouted, “I made electric wind?” 5. Why did William want to build another windmill?
Compare and Contrast- Take a few minutes and think about the character in the story. Compare and contrast your lives. You need at least 5 in each category. We have already discussed ages and times. Imagine you were given money to go to the mall with the main character of the book. List 10 items you would purchase and why. Then list 10 items he would purchase and why.
The Coriolis effect describes how Earth’s rotation affects moving objects. All free-moving objects or fluids, including wind, are deflected to the right of their path of motion in the Northern Hemisphere. In the Southern Hemisphere, they are deflected to the left.
Because the Earth rotates 15’ each hour, the rocket’s path is curved and veers to the right from the North Pole to the equator.
The apparent shift in wind direction is attributed to the Coriolis effect. This deflection: 1. Is always directed at right angles to the direction of airflow. 2. Affects only wind direction and not wind speed 3. Is affected by wind speed – the stronger the wind, the greater the deflections 4. Is strongest at the poles and weakens toward the equator, becoming nonexistent at the equator.
Friction acts to slow air movement, which changes wind direction. When air is above the friction layer, the pressure gradient causes air to move across the isobars. As soon as air starts to move, the Coriolis effect acts at right angles to this motion. The faster the wind speed, the greater the deflection.
The most prominent features of airflow high above the friction layer are the jet streams. Jet streams are fast moving rivers of air near the troposphere that travel between 120-240 kilometers per hour in a west-to-east direction.
Air close to Earth’s surface, the roughness of the terrain determines the angle of the airflow across the isobars. Over the smooth ocean surface, friction is low, and the angle of the airflow is small. Over rugged terrain, friction is higher, winds move more slowly and cross the isobars at greater angles.
Figure A – Upper level wind flow is balanced by the Coriolis effect and gradient pressure forces. Figure B – Friction causes surface force winds to cross isobars and move toward lower pressure areas.
Friction affects wind speed and direction. Coriolis effect affects wind direction only.
TopicMain Ideas Air Pressure DefinedAir pressure is the weight of air above. It is exerted in all directions. Measuring Air PressureAir pressure is measured with barometers, using the principle that fluids will deform if the weight of air is exerted on them. Factors Affecting WindPressure gradient, Coriolis effect, and friction
Using your notes and complete sentences answer the following essential questions. Be prepared to discuss your answer with the class.
Air pressure is exerted in all directions – down, up, and sideways. The air pressure pushing down on an object balances the air pressure pushing up on the object.
When air pressure increases, the mercury in the tube rises. When air pressure decreases, so does the height of the mercury column.
Solar radiation (the sun) is the ultimate source for wind.
The Coriolis effect deflects all free-moving objects to the right of their path of motion in the Northern Hemisphere. In the Southern Hemisphere, they are deflected to the left.
Explain how winds blow around pressure centers in the Northern and Southern Hemispheres. Describe the air pressure patterns within cyclones and anticyclones. Describe how friction controls the net flow of air around a cyclone and an anticyclone.
1. Describe how winds blow around pressure centers in the Northern and Southern Hemisphere. 2. Compare the air pressure for a cyclones and an anticyclones? 3. How does friction control net flow of air around a cyclone and an anticyclone? 4. How does the atmosphere attempt to balance the unequal heating of Earth’s surface?
ConceptHemisphere Cyclones rotate counter clockwise. Net flow of air is inward around a cyclone. Anticyclones rotate counterclockwise. Coriolis effect deflects winds to the right.
Lows, or cyclones (kyklon = moving in a circle) – are centers of low pressure. Highs, or anticyclones, are centers of high pressure.
In cyclones, the pressure decreases from the outer isobars toward the center. In anticyclones, just the opposite occurs, the values of the isobars increase from the outside toward the center.
The two most significant factors that affect wind are the pressure gradient and the Coriolis effect.
Winds move from higher pressure to lower pressure and are deflected to the right or left by Earth’s rotation. When the pressure gradient and the Coriolis effect are applied to pressure centers in the Northern Hemisphere, winds blow counterclockwise around a low. Around a high, they blow clockwise. In the Southern Hemisphere just the opposite happens. In either hemisphere, friction causes a net flow of air inward around a cyclone and a net flow of air outward around an anticyclone.
http://usatoday30.usatoday.com/weather/tg/whighlow /whighlow.htm http://usatoday30.usatoday.com/weather/tg/whighlow /whighlow.htm Read article as a class. Come up with questions using “Hot Science ?’s”
Atmospheric pressure at the Earth's surface is one of the keys to weather, which is one reason weather maps feature H's and L's, representing areas of high and low air pressure. High and low pressure areas are important because they affect the weather. The weather maps, such as those on television, show what's happening at the Earth's surface, and that's what we're talking about here. As the name says, a "high" is an area where the air's pressure is higher than the pressure of the surrounding air. A "low' is where it's lower. Meteorologists don't have any particular number that divides high from low pressure; it's the relative differences that count.
The pressure is high at the surface where air is slowly descending — much too slowly to feel. And, this is going on over a large area, maybe a few hundred square miles. As air descends, it warms, which inhibits the formation of clouds. This is why high pressure is generally — but not quite always — associated with good weather. The air that descends in high-pressure areas has to get to high altitudes in some way, and its done by rising in areas where the pressure at the surface is low. As air rises it cools. As the air cools, the humidity in it begins to condense into tiny drops of water, or if it's cold enough, into tiny ice crystals. If there's enough water or ice, rain or snow begin to fall. This is why low pressure is associated with bad weather. As shown in the graphic above, the air descending in high pressure flows out in a clockwise spiral in the Northern Hemisphere. Air flowing into an area of low pressure rises, making a counterclockwise spiral on the way in. For more on why the wind flows in the directions it does, go to the USATODAY.com Guide to the science of the atmosphere and look at the links from the section on "The what and why of the wind."Guide to the science of the atmosphere
Rising air is associated with cloud formation and precipitation.
Picture shows the relationship between surface convergence (inflow) and divergence (outflow) needed to maintain a low-pressure center. Surface convergence around a cyclone causes a net upward movement.
Low-pressure centers can produce bad weather in any season. Lows move roughly in a west-to-east direction across the United States. They require a few days up to more than a week to make the journey. Their paths can be somewhat unpredictable.
Underlying cause of wind is the unequal heating of Earth’s surface. Tropical regions, more solar radiation is received than is radiated back to space. Polar regions, less solar radiation is received than lost.
The atmosphere balances these differences by acting as a giant heat-transfer system. This system moves warm air toward high latitudes and cool air toward the equator.
The atmosphere transfers heat by moving warm air toward high latitudes and cool air toward the equator.
You will have 15 minutes to answer the essential questions in complete sentences. Remember be prepared to share your answer with the class.
ConceptHemisphere Cyclones rotate counter clockwise.Northern Net flow of air is inward around a cyclone. Both Anticyclones rotate counterclockwise.Southern Coriolis effect deflects winds to the right.Northern
In the Northern Hemisphere, winds blow counterclockwise and inward around a low, and clockwise and outer around a high. It is exactly opposite in the Southern Hemisphere.
In cyclones, air pressure decreases toward the center of the cell. In anticyclones, the air pressure increases toward the center of the cell.
The effect of friction is to cause a net flow of air inward around a cyclone and a net flow outward about an anticyclone.
The atmosphere acts like a huge heat-transferring system, transporting warm air from the equator toward the poles and cold air from the poles toward the equator.
1. What are local winds, and how are they caused? 2. Describe the general movement of weather in the United States. 3. What happens when strong, warm countercurrents flow along the coasts of Ecuador and Peru? 4. How is a La Nina event recognized?
PrecipitationLocationDominant Wind System Extremely low Extremely high
Small scaled winds produced by locally generated pressure gradient are known as local winds. The local winds are caused either by topographic effects or by variations in surface composition – land and water - in the immediate area.
Coastal areas in warm summer months, land surface is heated more intensely during the daylight hours than an adjacent body of water is heated. The air above the land surface heats, expands, and rises, creating an area of lower pressure. A sea breeze then develops because cooler air over the water at higher pressure moves towards the warmer land and low pressure air.
At night, the reverse occurs. Land cools more rapidly than the sea. A land breeze develops.
Two basic wind measurements: Direction Speed Winds are always labeled by the direction from which they blow. The instrument most commonly used to determine wind direction is the wind vane.
Commonly located on buildings and always point into the wind. Wind direction is often shown on a dial connected to it. Dial indicates wind direction by N, S, E, or W On a scale of 0’-360 ‘ Degree Scale for a weather vane. North = 0’ or 360’ East = 90’ South = 180’ West = 270’
How does the position of a wind vane tell you which direction the wind is blowing? The wind vanes point into the wind.
When wind consistently blows more often from one direction than from any other, it is called a prevailing wind. In the United States, the westerlies consistently move weather from west to east across the continent.
Winds associated with the westerlies, as measured at the surface, often vary considerably from day to day and from place to place. The direction of airflow associated with the trade winds is much more consistent.
Anemometer - anemo = wind, metron = measuring instrument A cup anemometer is commonly used to measure wind speed. The wind speed is read from a dial much like the speedometer of an automobile.
You will be given 8 words from the chapter Cut them into squares Use the squares to make a word chain. Put the chain together so it shows a relationship among the words. There is more than one way to make a chain. Once you have completed the chain glue it to the top of your paper. On the bottom half of the paper, use the chain to write a paragraph that uses all the words.
The cold Peruvian current flows toward the equator along the coasts of Ecuador and Peru. This flow encourages upwelling of cold nutrient-filled waters that contain the food source for millions of fish, particularly anchovies. Near the end of the year, a warm current that flows southward along the coasts of Ecuador and Peru replaces the cold Peruvian current.
At regular intervals of three to seven years, these warm countercurrents become unusually strong and replace normally cold offshore waters with equatorial waters. They call these episodes of ocean warming that affect the eastern tropical Pacific El Nino.
Usually strong countercurrents accumulate large quantities of warm water that block the upwelling of colder, nutrient-filled waters. Some inland areas that are normally arid receive an abnormal amount of rain.
An episode occurring every three to seven years – of ocean warming that affects the eastern tropical Pacific. Warm countercurrents become unusually strong and replace normally cold offshore waters with equatorial waters.
When surface temperatures in the eastern Pacific are colder than average, a La Nina event is triggered that has a distinctive set of weather patterns. Winter blows colder than normal air over the Pacific Northwest and northern Great Plains. The Northwest also experiences more precipitation. It warms much of the rest of the United States. Can increase hurricane activity.
Both have a great affect on world climate and vary greatly. These phenomena remind us that the air and ocean conditions of the tropical Pacific influence the state of the weather almost everywhere.
You will have 15 minutes to answer the essential questions in complete sentences. Remember be prepared to share your answer with the class.
Local winds are small scaled winds caused by local variations in air pressure, which are caused by topography and unequal heating of land and water, or unequal heating of air above slopes and valleys.
Weather generally moves from west to east in the United States.
An El Nino event blocks normal upwelling of cold, nutrient-laden waters off the shores of these countries, and causes heavy precipitation island. El Nino can have far-reaching effects on weather patterns of regions that are great distances from Ecuador and Peru.
La Nina is triggered when surface temperatures in the eastern Pacific are colder than average.
PrecipitationLocationDominant Wind System Extremely lowArabian DesertSinking trade winds produce tropical high Extremely highAmazon Rain ForestRising trade winds produce equatorial low