Composition of the atmosphere; Contains layers based on altitude and pressure Nitrogen @ 78%, from volcanic eruptions and when dead plants and animals decay. Oxygen @ 21%, produced mainly from plants. CO 2, Argon, water vapor and other gasses @ 1%, water vapor is the only substance that exists in the atmosphere as a solid, liquid and gas.
Life Science Connection Photosynthesis and respiration are linked to gas exchange between organisms and the atmosphere. Photosynthesizing plants use CO 2, water and light energy to produce oxygen. During respiration, plants and animals consume oxygen and release CO 2.
Troposphere The layer in which we live and is 90% of the total mass, contains almost all of the Earths’ CO 2, H 2 O vapor, clouds, air pollution, life-forms and weather.
Stratosphere The atmospheric layer above the troposphere is called the stratosphere. In the stratosphere, the air is very thin and contains little moisture. The lower stratosphere is extremely cold, measuring about -60 0 C. In the stratosphere, the temperature rises with increasing altitude. This occurs because of ozone.
OZONE Ozone is a molecule that is made up of three oxygen atoms. Almost all of the ozone in the atmosphere is contained in the ozone layer of the stratosphere. Ozone absorbs solar energy in the form of ultraviolet radiation, warming the air. By absorbing the ultraviolet radiation, the ozone layer also protects life at the Earth’s surface.
Mesosphere Above the stratosphere is the mesosphere. The mesosphere is the coldest layer of the atmosphere. As on the troposphere, The temperature drops with increasing altitude. Temperatures can be as low as -93 0 C at the top of the mesosphere. Scientists have recently discovered large wind storms in the mesosphere with winds reaching speeds of more than 320 km/h.
Thermosphere This is the uppermost layer of the atmosphere and the temperature will increase with altitude because the many gasses absorb solar radiation and can reach temperatures of 1,700 0 C. While the thermosphere has very high temperatures, it would not feel hot. Temperature and heat are not the same thing.
Thermosphere (contd.) Temperature is the measure of the average energy of particles in motion. A high temperature means that the particles are moving very fast. Heat, on the other hand, is the transfer of energy between objects of different temperature. But in order to transfer energy, particles must touch each other. Part of the thermosphere is the Ionosphere.
IONOSPHERE In the upper mesosphere and the lower thermosphere, nitrogen and oxygen atoms absorb harmful solar energy, such as X- rays and gamma rays. This absorption not only contributes to the thermosphere’s high temperatures but also causes the gas particles to become electrically charged. Electrically charged particles are called ions: therefore, this part of the thermosphere is called the ionosphere.
QUIZ 1.What are the two main gasses in Earth’s atmosphere? 2.What is atmospheric pressure? 3.Name the layers of the atmosphere, starting with the one closest to the Earth. 4.What is the ozone layer and why is it important to Earth?
ANSWERS 1.Nitrogen and Oxygen 2.Atmospheric pressure is the force exerted by molecules of air on a surface. 3.Troposphere, Stratosphere, Mesosphere, Thermosphere. 4.The ozone layer is a layer of ozone molecules in the stratosphere. The layer filters ultraviolet radiation from the sun and prevents much of this radiation from reaching Earth.
The Earth receives energy from the sun by radiation. Radiation is the transfer of energy from the sun by electromagnetic waves. Although the sun releases a huge amount of energy, the Earth receives only about two-billionths of this energy. Yet even this small amount of energy has a very large impact on Earth. Like standing in the sun, you can feel the warmth.
Conduction This is the transfer of thermal energy from one material to another by direct contact. Like walking on hot cement or sand. Thermal energy always moves from hot to cold.
Convection Most thermal energy in the atmosphere moves by convection. Convection is the transfer of thermal energy by the circulation or movement of a liquid or gas. Warm air is less dense and rises as it cools and becomes denser it sinks. This continual process creates a circular movement of air called convection current.
The Greenhouse Affect The gasses in the atmosphere act like the layer of glass in the greenhouse trapping the heat. Thermal energy is absorbed by objects in the greenhouse and then radiates this heat warming the air. Not all gasses in the atmosphere trap thermal energy, the ones that do are called greenhouse gasses. Some scientists believe that global warming is a cycle of the earth but is being accelerated by the burning of fossil fuels.
Global Warming In recent decades, many scientists have become concerned that an increase in greenhouse gasses, particularly carbon dioxide, may be causing an increase in the greenhouse effect. These scientists have hypothesized that a rise in carbon dioxide as a result of human activity has led to an increased global temperature. A rise in average global temperatures is called global warming.
QUIZ 1.What is radiation? 2.What is a convection current? 1.Energy transferred as electromagnetic waves. 2.The continual, circular movement of warm and cool particles in a liquid or gas.
Why Air Moves Wind is created by differences in air pressure. The greater the pressure difference is, the faster the wind moves. This difference in air pressure is generally caused by the unequal heating of the Earth. For example, the air at the equator is warmer and less dense. This warm less dense air rises.
Why Air Moves (contd.) As it rises, it creates an area of low pressure. At the poles, however, the air is colder and more dense. Colder, more dense air is heavier and sinks. This cold, sinking air creates areas of high pressure. Pressure differences in the atmosphere at the equator and at the poles cause air to move. Because air moves from areas of high pressure to areas of low pressure, winds generally move from the poles to the equator.
PRESSURE BELTS As warm air rises over the equator, it begins to cool. Eventually, it stops rising and begins moving towards the poles. At about 30 0 north and 30 0 south latitude, some of the cool air begins to sink. This cool, sinking air causes a high pressure belt near 30 0 north and 30 0 south latitude. At the poles, cold air sinks. As this air moves away from the poles and along the Earth’s surface, it begins to warm.
PRESSURE BELTS (contd.) As the air warms, the pressure drops, creating a low-pressure belt around 60 0 north and 60 0 south latitude. The circular patterns caused by the rising and sinking of air are called convection cells.
Coriolis Effect The movement of the wind is affected by the rotation of the earth and causes the air currents to travel in a curved pattern.
Coriolis Effect (contd.) Winds don’t blow directly north or south. The movement of wind is affected by the rotation of the Earth. The Earth’s rotation causes the wind to travel in a curved path rather than a straight line. The curving of moving objects, such as wind, by the Earth’s rotation is called the Coriolis effect.
Coriolis Effect (contd.) Because of the Coriolis effect, the winds in the Northern Hemisphere curve to the right, and those in the Southern Hemisphere curve to the left.
WEiRD SCIENCE In addition to affecting the ocean and atmosphere currents, the Coriolis effect can also be observed in river systems. Rivers in the Northern Hemisphere erode their right banks more than their left banks. Because the Mississippi River and the Yukon River flow roughly north-south in sections, they are good examples of this effect.
Types of Winds Two main types wind; both types are caused by uneven heating of the Earth. Local Winds and Global Winds. Wind is moving air.
Local Winds Local Winds can blow from any direction and usually only travel short distances. These are affected by the geography of an area. The land will heat up faster than water and cools faster at night creating high and low pressures and a breeze.
Global winds Global winds are part of a pattern of winds that circulate and moves across the earth.
Trade winds Trade winds, are in both hemispheres, these are winds that blow from 30 0 latitude towards the equator and curve due to the Coriolis effect.
WESTERLIES The westerlies are wind belts found in both the Northern and Southern Hemispheres between 30 0 and 60 0 latitude. The westerlies flow towards the poles in the opposite direction of the trade winds. The westerlies helped early traders return to Europe.
Jet Streams Jet Streams are narrow belts of high speed air that blow in the upper troposphere and lower stratosphere at speeds up to 500km/hr.
QUIZ 1.What is wind? 2.How does air temperature over landmasses and adjacent bodies of water change between night and day? 3.What is the Coriolis effect? 1.Air that flows between air masses of different pressures and temperatures. 2.During the day, the air is cooler over water. At night, the air is cooler over land. 3.The deflection of moving objects due to Earth’s rotation.
Types of Air Pollution Primary pollution; These are pollutants that are put directly into the air by humans or natural activity. Like exhausts from vehicles and volcanic eruptions.
Types of Air Pollution (contd.) Secondary pollution; is formed from chemical reactions that occur when primary pollutants come in contact with other primary pollutants or with naturally occurring substances like water vapor. Many secondary pollutants are formed when a primary pollutant reacts with sunlight.
Human-caused air Pollution Human-caused air pollution comes from a variety of sources. The major source of air pollution today is transportation. Cars contribute about 60% of the human- caused air pollution in the United States. The oxides that come from car exhaust, such as nitrogen oxide, contribute to smog and acid rain. Oxides are chemical compounds that contain oxygen and other elements.
INDUSTRIAL AIR POLLUTION Many industrial plants and electric power plants burn fossil fuels to get their energy. But burning fossil fuels causes large amounts of oxides to be released into the air. In fact, the burning of fossil fuels in industrial and electric power plants is responsible for 96% of the sulfur oxides released into the atmosphere.
INDOOR AIR POLLUTION Air pollution is not limited to the outdoors. Sometimes the air inside a home or building is even worse than the air outside. The air inside a building can be polluted by the compounds found in new carpets, paints and building materials can also add to IAP, especially if the windows and doors are tightly sealed.
The Air Pollution Problem Air pollution is both a local and global concern. Local air pollution such as smog, generally affects large cities. Air pollution becomes a global concern when local pollution moves away from its source. Winds can move pollutants from one place to another, sometimes reducing the amount of pollution in a source area but increasing it in another place.
Acid Precipitation Precipitation that contains acids from air pollution is called acid precipitation. When fossil fuels are burned, they release oxides of sulfur and nitrogen into the atmosphere. When these oxides combine with water droplets in the atmosphere, they form sulfuric acid and nitric acid, which fall as precipitation. Acid precipitation has many negative effects on the environment.
The Clean Air Act The Clean Air Act helps to control industrial pollution by requiring that scrubbers are used to remove pollutants from coal burning plants. It also controls the amount of pollutant allowed from each source.
QUIZ 1.Classify each of the following as either a primary or a secondary pollutant. 2.What are the three sources of air pollution. 1.Primary pollutants are tobacco, smoke and chalk dust. Secondary pollutants are smog and acid rain. 2.Motor vehicles, industries, electric power plants.