Atmosphere Stuff WEATHER AND CLIMATE. Practice. Answer:

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1 Name Atmosphere Stuff Period Read each topic and hi-lite/annotate Answer practice questions to review your understanding Watch videos and draw diagrams when required WEATHER AND CLIMATE We refer to the local, short-term conditions in an area as weather. This includes temperature, humidity, cloud cover, precipitation, wind speed, and atmospheric pressure. But weather only happens on time scales from seconds to days. The average weather in an area over a long period of time (at least several decades) is called climate. Climate is defined by temperature and precipitation and is what determines plants in an area, which in turn, determines animals. There are six different factors that affect the distribution of heat and precipitation around the world, thus leading to varying climates. These six factors are unequal heating of Earth by the Sun, atmospheric convection currents, the rotation of Earth, Earth s orbit around the sun on a tilted axis, ocean currents, and Earth s topography. We will start with general information about the atmosphere, then explore these six climatedetermining factors. Which of the following is the best description of a region s climate? A. The amount of rainfall that an area receives over a period of 1 year. B. The average precipitation over a 1-2 year time period. C. The average high temperature of a region. D. The average temperature and precipitation over several decades. E. The average temperature and rainfall over a period of 1-2 years. Answer: 1

2 Take a deep breath. About 99% of the volume of air you inhaled consists of two gases: nitrogen (78%) and oxygen (21%). The remainder consists of water vapor (varying from 0.01% at the frigid poles to 4% in the humid tropics, for an average of about 1%), 0.93% argon (Ar), 0.039% carbon dioxide (CO 2) and trace amounts of dust and soot particles as well as other gases including methane (CH 4), ozone (O 3), and nitrous oxide (N 2O). Review Question: The atmosphere is 78% nitrogen but it is in a form we are unable to utilize. Describe how we are able to convert nitrogen gas (N 2) into a more useable form (use appropriate vocab, feel free to draw diagram) EARTH S ATMOSPHERE The density of the gas molecules per unit of air volume varies throughout the atmosphere because gravity pulls its gas molecules toward the earth s surface. About 75-80% of the earth s air mass is found in the atmospheric layer closest to earth s surface the troposphere. This layer extends about 11 miles above sea level at the equator and 4 miles above sea level over the poles. Most of the weather we experience occurs in this layer. Air currents, winds, and concentrations of CO 2 and other greenhouse gases in the troposphere play a major role in the planet s weather and climate. The layers of the atmosphere are based on differences in temperature as altitude increases. Because of radiation from Earth and the objects on it, the troposphere is warmer at sea level (0 km altitude) and cools as altitude increases. Moving away from Earth, the next layer of the atmosphere is the stratosphere. The stratosphere contains a layer of air with a high concentration of ozone molecules (O 3), called the ozone layer. Stratospheric ozone is formed when oxygen molecules (O 2) in this layer interact with ultraviolet (UV) radiation from the sun. The ozone layer keeps about 95% of the sun s harmful UV radiation from reaching the earth s Sketch and label: s.htm atmospheric layers (4) temperature ozone layer 2

3 surface. This UV filtering effect allows life to exist on Earth and protects us from sunburn, skin and eye cancers, cataracts, and damage to our immune systems. This absorption of UV also makes the stratosphere warm as altitude increases, a trend opposite to that of the troposphere. Above the stratosphere is the mesosphere and then the thermosphere. Without any heat absorbing materials, the mesosphere is the coldest layer of the atmosphere. The thermosphere is sometimes broken down further into the ionsphere (an area of highly charged particles where auroras occur) and the exosphere (where many satellites orbit). Despite this distinction, the entire thermosphere warms as altitude increases. Although there is no distinct beginning or end to any of the layers, the transition from one to another is known as a pause. For example, the transition from troposphere to stratosphere is called the tropopause. The stratopause divides the stratosphere and mesosphere and the mesopause divides the mesosphere and thermosphere. There is no pause after the thermosphere because it blends into space as the concentration of atmospheric molecules gets lower and lower. : In which level of the atmosphere does weather occur? A. Troposphere B. Stratosphere C. Mesosphere D. Thermosphere E. Exosphere Which level of the atmosphere is the densest? A. Troposphere B. Stratosphere C. Mesosphere D. Thermosphere E. Exosphere What best describes the density of the atmosphere? A. It increases as you increase in altitude B. It decreases as you increase in altitude C. It maintains a constant level throughout the atmosphere D. It shows fluctuations up and down as you move through the layers of the atmosphere E. It does not change What is the importance of the ozone layer? A. It plays an important role in the greenhouse effect. B. It reflects solar gamma reaction that would otherwise reach Earth s surface. C. It acts as an insulator for the earth and helps to maintain a livable temperature. D. It absorbs incoming UV rays. E. It reflects incoming heat back into space. 3

4 UNEQUAL HEATING OF EARTH Factor 1: Variation in Sun s Angle Because of Earth s spherical shape, sunlight strikes the earth at a perpendicular angle only at the equator. As you move away from the equator, the sun s rays hit the earth at a more oblique angle. When the angle is more oblique, the sunlight must travel a longer distance through the atmosphere. This allows for a lot of energy to be absorbed by the atmosphere, leaving little to hit the earth. Near the equator, sunlight travels only a short distance through the atmosphere, less energy is absorbed, and more energy is left to hit the earth. : What region of the earth does the sun hit at the most direct angle? A. North Pole (90 N) D S B. South Pole (90 S) E. Equator (0 ) C N Which of the following is not true about the sun s energy heating the earth? A. The sun s rays hit the earth at different angles depending on the latitude. B. The sun s rays are concentrated over a smaller surface area at the equator than they are in higher latitudes. C. The polar regions reflect more sunlight than the tropical regions. D. The sun s rays are more strongly reflected in the lower latitude regions. E. The unequal heating helps to determine an area s climate. s_ecliptic.html Factor 2: Angle of incidence Air is heated much more at the equator, where the sun s rays strike directly, than at the poles, where sunlight strikes at an angle and spreads out over a much larger area. These differences in energy input help explain why tropical regions near the equator are hot, why polar regions are cold, and why temperate regions in between generally have warm and cool temperatures. The intense input of solar radiation in tropical regions leads to greatly increased evaporation of moisture from forests, grasslands, and bodies of water. As a result, tropical regions normally receive more precipitation than other areas of Earth. Factor 3: Albedo We will discuss later EARTH S TILT AND SEASONS The earth is tilted 23.5 on its axis. The North Pole is always pointed toward the North Star. During the spring equinox (first day of spring), the equator (0 latitude) is facing directly toward the sun. In this neutral position, the equator is getting the most direct sunlight and the rest of the earth is getting indirect sunlight. (Reread the Unequal Heating of Earth summary if necessary.) Six months later, at the autumn equinox, the earth is in the same position except on the opposite side of its revolution around the sun. During summer and winter, the northern hemisphere is tilted either toward (summer) or away from (winter) the sun. This means during our summer, our angle of Use the above website to manipulate the sun and Earth to determine the cause of the seasons. June marks Summer in the Northern hemisphere draw. Draw the relationship of the sun and Earth during this time. (Shapes not to scale). Draw North America, include the tilt of the axis of Earth (you can use a line through the poles), draw a line to represent the equator, shade the part of Earth that is in darkness and include arrows to indicate solar radiation hitting Earth from the sun. December marks Summer in the Northern hemisphere draw. Draw the relationship of the sun and Earth during this time. (Shapes not to scale). Follow the same directions from above 4

5 incidence is higher and therefore we receive more energy per unit area and experience a higher average temperature. The opposite is true for our winter when we are tilted away from the sun. Because the earth is only tilted 23.5 and we are at 40 N, we never get the sun s most direct rays. During our summer, the direct rays shine on 23.5 N latitude, the Tropic of Cancer. During our winter, the direct rays shine on 23.5 S latitude, the Tropic of Capricorn. The area between these two tropics (equatorial region) is always receiving a lot of concentrated solar energy and stays warm year round. But since the warmest area shifts, so does the rain (formed when warm air rises, cools, and releases water as precipitation). Areas just north and south of the equator stay warm but may experience dry seasons during their respective winters. A common misconception is that the earth is closer to the sun in the summer and farthest from the sun in the winter. Actually, Earth s perihelion (peri=near, helios=sun) occurs around January 3. Earth s aphelion (apo=away) occurs around July 4. The difference between these two distances is only about 5 million kilometers (about 3% of the distance to the sun), not enough to affect temperature. Earth s tilt and its effect on the angle of incidence is the determining factor when it comes to seasons. The primary cause of Earth s seasons is the A. Constant tilt of Earth s rotational axis with respect to the plane of its orbit around the Sun B. Changing distance of Earth from the Sun at different times of the year C. Periodic wobbling of Earth on its axis of rotation D. Changing relative positions of Earth, its Moon and the Sun E. Periodic changes in solar energy output What latitude receives the most direct sunlight throughout the year? A. 90 N B N C. 0 D S E. 90 S 5

6 EARTH S ROTATION AND THE CORIOLIS EFFECT In the northern hemisphere, large air masses generally appear to curve clockwise and in the southern hemisphere, they appear to curve counterclockwise. This curving pattern is a result of the earth s rotation in an eastward direction as winds move above the surface. The apparent curvature of object traveling long distances on Earth is known as the Coriolis effect. On a global scale, this effect produces steady, reliable wind patterns, such as the trade winds and mid-latitude Westerlies. Ocean currents also experience the Coriolis effect and curve clockwise in the northern hemisphere and counterclockwise in the southern hemisphere. Imagine you are in space looking down at the North Pole (the center of your field of view). As the earth spins on its axis, the North Pole is moving much slower than the equator because it s a much smaller area. In 24 hours a point near the North or South Pole (Point A) will not travel nearly as far as a point near the equator (Point B). An object (like a large mass of air or water) traveling from Point B to Point A will be moving faster than the middle portion of the hemisphere and will end up to the right of Point A. The same object traveling from A to B will be moving slower than Point B and will land behind Point B. Both examples show a clockwise (to the right) curve according to the point of origination. The same effect is seen in the southern hemisphere, with object appearing to curve counterclockwise (to the left) according to the direction they came from. Large masses of air, moving long distances, like Earth s atmospheric convection cells are influenced by the Coriolis effect. This is seen in the world s prevailing winds. The six major wind belts (formed by the six convection cells) all curve clockwise in the northern hemisphere and counterclockwise in the southern hemisphere. The winds on either side of the equator are the Northeast and Southeast trade winds. From are the Westerlies. At the North and South Pole are the polar easterlies. Winds are always named for the direction they come from. 6

7 Watch the following video about the Coriolis Effect: If you threw a paper airplane North from Texas what is the most likely place it would land: A. California B. Nebraska C. Delaware D. Mexico An object moving from the Equator south would move to the (assuming you were facing South) Identify the hurricane of the hurricane pictures below (Northern or Southern Hemisphere) Which of the following statements about the Coriolis Effect is incorrect? A. The Coriolis effect causes object to be deflected to the right in the northern hemisphere. B. The Coriolis effect causes objects to be deflected clockwise in the southern hemisphere. C. Global winds are not affected by the Coriolis effect. D. The Coriolis effect is caused by the rotation of the earth. E. The different rotation speeds of Earth at different latitudes causes the deflection of traveling objects. The Coriolis effect and prevailing winds contribute to the formation of gyres in the oceans. Which direction do these gyres flow in the Northern Hemisphere? A. North to South D. Counterclockwise B. South to North E. East to West C. Clockwise A plane leaves the North Pole. Initially, it flies directly south towards point B on the diagram. Which is the most likely landing site for the plane if it maintains a straight path to the south? A, B, C, or D? 7

8 ATMOSPHERIC CONVECTION CURRENTS Four properties of air influence its movement around the world. 1. Density. Warm air is less dense so it rises. Cool air is denser so it sinks. 2. Water Vapor Capacity. Warm air can hold more water vapor than cold air. This helps explain why summer days in Indiana are hot and humid and winter days are cold and dry. The maximum amount of water vapor that air can hold is called its saturation point. The saturation point is higher for warm air because it can hold more water. Conversely, the saturation point is lower for cool air because it can hold less water. As air cools, the saturation point lowers and the air can t hold any more water vapor. The water vapor will condense and leave the air as precipitation. 3. Adiabatic Cooling/Heating. As air rises, the pressure lowers. This allows molecules to move further apart (and collide less), cooling the temperature of the air. When air sinks, the pressure rises, causing molecules to collide more and the temperature to rise. This forced change in temperature because of change in pressure is called adiabatic cooling or heating. 4. Latent Heat Release. When water evaporates (liquid to gas) a tiny amount of energy is stored. This energy is known as latent heat. The latent heat will be released when the opposite process occurs and the water condenses into a liquid. Whenever precipitation is forming and latent heat is being released, the air will warm and rise. Because the earth is heated unevenly, some areas experience the warm, less dense, wet, rising air and some areas experience cool, denser, dry, sinking air. The warmest air is found near the equator (in the intertropical convergence zone) where heat from the sun is most direct. This solar energy evaporates ocean water and transfers heat from the oceans to the atmosphere. Once the air has cooled and released precipitation, it will sink back down as cooler, drier air. This continuous cycle of rising and falling air creates large convection currents of air around the earth. Along with rising and falling air, air moves across the surface of the earth from areas of high pressure to areas of low pressure. This continual displacement and replacement of air forms large convection cells. Hadley cells are convection cells north and south of the equator. Polar cells are convection cells at the north and south pole. In the area between (where we live) air circulates based on the Hadley and polar cells but does not form a strong convection cell. This is partly why we experience a variety of different weather conditions, even during the same season. 8

9 Watch the video lectures to help you label the diagram (you might have to Google as well): On the diagram to the left draw and label the following: - High and Low Pressure - Hadley Cells (with arrows) - Westerlies - Easterlies - Ferrel Cells (with arrows) - Polar Cells (with arrows) What happens to air as it rises? A. The pressure decreases and it expands in volume. B. The pressure increases and it expands in volume. C. The pressure decreases and it decreases in volume. D. The pressure increases and it decreases in volume. E. The pressure and volume remain constant. What is the overall direction of global air currents at the equator? A. Air rises at the equator. B. Air sinks at the equator. C. Air moves horizontally to the north at the equator. D. Air moves horizontally to the south at the equator. E. Air is relatively stable at the equator. What is the best explanation for the high amounts of rain that occur at the equator? A. This area experiences a high amount of wind, which leads to storms and rain. B. This area has a large amount of water, leading to more rain. C. The warm air rises at the equator and condenses at a high altitude, leading to rain. D. The low pressure system that develops here causes warm air to sink, leading to rain. E. As the air rises, it becomes warmer, leading to more rain. What type of weather would you expect to find at the intertropical convergence zone (ITCZ)? A. Dry and warm weather B. Dry and cool weather C. Warm and rainy weather D. Cool and rainy weather E. Warm in the summer and cool in the wi 9

10 OCEAN CURRENTS Along with unequal heating of the earth, atmospheric convection currents, the rotation of the earth and the Coriolis effect, and Earth s orbit around the sun on a tilted axis, Earth s weather and climate are also influenced by the circulation of surface and deep ocean waters. Sunlight warms the ocean s surface but does not penetrate deeply, so ocean water is warmest at the surface and becomes colder with depth. Surface waters receiving more solar radiation at the equator are warmer than surface waters in temperate or polar regions. Like air, warm water is less dense than cool water. This leads to a heavy layer of cold, salty, sinking water under a lighter, warmer, less salty layer. The high heat capacity of water allows it to absorb a lot of solar radiation and remain relatively stable in temperature. By absorbing and releasing heat to the atmosphere, the oceans regulate Earth s climate. Oceans also influence climate by moving heat from place to place via surface circulation. Large-scale ocean currents (gyres) are driven by temperature, prevailing winds, and gravity. Surface currents flow horizontally great distances across the globe, curving according to the Coriolis effect and the location of continents. Equatorial ocean currents carry warm water to cooler regions. Cool water currents carry water from high latitude regions or from deep in the ocean. Surface currents like the Gulf Stream are rapid and powerful, bringing warm water from the Gulf of Mexico to Europe, moderating the continent s climate, which would otherwise be much colder. Surface winds and heating also create vertical currents in the ocean. Upwelling, the upward movement of cold, deep water toward the surface, occurs where horizontal currents diverge or flow away from one another. Cold, upwelled water is rich in nutrients and generally high in productivity. Deep in the ocean, vertical currents create rising and falling convection cells, like those in the air. The worldwide current system in which warmer, fresher water moves along the surface and colder, saltier water moves deep beneath the surface is known as thermohaline circulation. Scientists hypothesize that melting of Greenland s ice sheet, because of climate change, may make North Atlantic waters less salty and less likely to sink. This change could trigger a shutdown of thermohaline circulation, causing temperate areas like Europe to rapidly cool. What is one major role that these gyres play in global climate? A. Currents redistribute heat from the North to the South B. Currents redistribute heat from the Equator to Northern latitudes C. Drive global wind patterns in the Northern hemisphere D. Contribute to the Coriolis effect E. Currents redistribute tropical moisture 10

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12 El Niño Southern Oscillation Another interaction between ocean currents and the atmosphere that influences climate is the El Niño-Southern Oscillation (ENSO), a naturally occurring shift in atmospheric pressure, sea surface temperature, and ocean circulation in the tropical Pacific Ocean. Under normal conditions, Northeast and Southeast trade winds blow along the equator, from a region of high pressure in the eastern Pacific to one of low pressure in the western Pacific, forming a large-scale convection loop in the atmosphere. The winds push surface waters westward, causing warm surface water to pile up in the western Pacific. As a result, water near Indonesia can be up to 8 C warmer than water near South America. The westward-moving surface waters are replaced by cold water rising up from the deep in a nutrient-rich upwelling along the coast of Peru and Ecuador. El Niño conditions are triggered when air pressure decreases in the eastern Pacific and increases in the western Pacific, weakening the equatorial winds and allowing warm water to flow eastward. This suppresses upwelling along the Pacific coast of the Americas, shutting down the delivery of nutrients that support marine life and fisheries. El Niño events alter weather patterns around the world, creating rainstorms and floods in areas that are generally dry (like southern California) and causing drought and fire in regions that are typically moist (like southern Africa and Southeast Asia). What is a positive effect of upwelling? A. Creates an area of high precipitation B. Creates an area of high nutrient levels along the coast C. Creates an area of high nutrients in the center of the ocean basin D. Creates an area of low precipitation E. Brings warm water to the surface of the ocean El Nino tutorial video: Notes: Which of the following is true about ENSO? I. Upwelling is suppressed off the coast of South America II. This phenomenon is human caused and related to global warming III. The tradewinds weaken, allowing warm water to move eastward A. I only B. II only C. III only D. I and III E. I, II, and III 12

13 THE RAIN SHADOW EFFECT Many of the processes that affect weather and climate occur on a global scale, but local features, like topography (the shape of the land) also play a role. Climbing in elevation causes a much more rapid change in climate than moving the same distance toward the poles. There is a distinct change in vegetation along mountain slopes that corresponds with this altitude-induced climate change. When large masses of air encounter mountain ranges, the air is forced upwards. This rising air experiences the same changes as rising air at the equator: it cools, expands, releases water vapor as precipitation, and decreases in pressure. All the rain on this (windward) side of the mountain range often leads to lush vegetation. By the time the air flows over the mountain and back down the other side, it has released most of its water and is very dry. The warm, dry, arid side is called the leeward side and is known as the rain shadow region. This rain shadow effect can be seen in the Sierra Nevada range in the Western United States. Look at the graph below. Notice how precipitation rises on the windward side of each mountain range and falls on the leeward side of each mountain range. The rain shadow effect can have a large effect on local climate. When the rain shadow effect is occurring, which side of the mountain tends to receive more rain? A. Windward side B. Leeward side C. Top of the mountain D. Foot of the mountain E. Side of the mountain that does not face the ocean Which of the following statements explains the rain shadow effect? A. Mountains force air to rise; air cools and releases moisture as it rises. B. The atmosphere gets denser as elevation increases, causing snow to fall. C. Temperatures are higher on one side of a mountain than the other. D. Wind patterns cause precipitation E. Lush vegetation on one side of a mountain causes it to rain more on this side 13