Chapter 12, Earth's Atmosphere

Jet Stream

A narrow band of high winds near the top of the troposphere. Flows around Earth from west to east, often making large loops to the north or the south. Influences weather as they move cold air from the poles toward the tropics and warm air from the tropics toward the poles. Can move at speeds up to 300 km/h. More unpredictable than prevailing winds.

Temperature Inversion

A temperature inversion occurs in the troposphere when temperature increases as altitude increases. Ground level air is almost the same temperature as higher-altitude air. The air is stable, and convection currents are weak. A layer of cooler air is trapped by a layer of warmer air above it. This prevents air from mixing and can trap pollution in the air close to Earth's surface.

Air Pollution

Air pollution is the contamination of air by harmful substances including gases and smoke. Air pollution is harmful to humans and other living organisms. Years of exposure to polluted air can weaken a human's immune system. Respiratory diseases such as asthma can be caused by air pollution. Air pollution comes from many sources. Point-source pollution is pollution that comes from an identifiable source. Examples include smokestacks from large factories, and electric power plants. Nonpoint-source pollution is pollution that comes from a widespread area. Examples include pollution in a large city.

Convection

Convection is the transfer of thermal energy by the movement of particles within matter. As molecules of air close to Earth's surface are heated by conduction, they spread apart, and air becomes less dense. The less dense air rises, transferring thermal energy to higher altitudes. Conduction is seen as boiling water circulates and steam rises.

Particulate Matter

Particulate matter is a mixture of dust, acids, and other chemicals that can be hazardous to human health. The smallest particles are the most harmful. Children and older adults are most likely to experience health problems from particulate matter. Particulate matter in the atmosphere absorbs and scatters sunlight.

Photochemical Smog

Photochemical smog is air pollution that forms from the interaction between chemicals in the air and sunlight. Smog forms when nitrogen dioxide, released in gasoline engine exhaust, reacts with sunlight. A series of chemical reactions produces ozone or other compounds that form smog. Ground-level ozone can harm the tissues of plants and animals.

Prevailing Winds

Prevailing Winds - relatively steady, predictable winds caused by differences in air pressure and the Coriolis Effect. Other prevailing winds include polar easterlies and trade winds.

Westerlies

Prevailing westerlies are in the mid-latitudes, between 30º and 60° north and south; they blow from the west to the east. They play an important part in the weather of the United States.

Atmosphere

The atmosphere is a thin layer of gases surrounding Earth. Earth's atmosphere is divided into five layers. The first four extend about 600 km, and the outermost layer extends about 10,000 km above Earth. The atmosphere contains oxygen, carbon dioxide, and water necessary for life on Earth. The atmosphere acts like an insulation house, and helps keep the temperatures on Earth within range in which living organisms can survive. Without it, daytime temperatures would be extremely high and nighttime temperatures would be extremely low. The atmosphere also helps protect living organisms from harmful rays from the Sun.

Ionosphere

The ionosphere is a region within the mesosphere and thermosphere that contains ions. Between 60 km and 300 km above Earth's surface, the ionosphere ions reflect AM radio waves transmitted at ground level. After sunset when ions recombine, this reflection increases. AM radio waves can travel long distances, especially at night, by bouncing off Earth and the ionosphere.

Troposphere

The atmospheric layer closest to Earth's surface is called the troposphere. Most people spend their entire lives in the troposphere. It extends from Earth's surface to altitudes between 8-15 km. The word "tropos" comes from the Greek word meaning to change. The temperature in the troposphere decreases as you move away from Earth's surface. The warmest part of the troposphere is near Earth's surface.

Stratosphere

The atmospheric layer that is directly above the troposphere is called the stratosphere. The stratosphere extends from 15 km to about 50 km above Earth's surface. The upper half of the stratosphere contains the most amount of ozone gas.

Local Winds

Local Winds are like global winds, these occur where air pressure is different from one location to another due to the unequal heating of Earth's surface. These occur over short distances while global winds occur over long distances. Local winds include sea breezes and land breezes.

Greenhouse Effect

The land, water, plants, and other organisms absorb solar radiation that reaches Earth's surface. The radiation absorbed by Earth is re-radiated, or bounced back, into the atmosphere. This in the form of infrared radiation (IR), which heats the atmosphere. Some of the gases in the atmosphere, called greenhouse gases, prevent some of Earth's IR energy from escaping. Greenhouse gases trap IR and direct it back to Earth's surface. This causes a buildup of thermal energy at Earth's surface. The gases that trap IR best are water vapor, carbon dioxide and methane. This process is called the greenhouse effect.

Wind

Warm air rises and puts less pressure on Earth than cooler air. Because it's warm in the tropics, air pressure is usually low. Over colder areas, such as the North Pole and South Pole, air pressure is usually high. This difference in pressure creates wind. Wind is the movement of air from areas of high pressure to areas of low pressure. Global wind belts influence weather and climate on Earth.

Sea Breeze

Wind that blows from a sea or lake to the land due to local temperature and pressure differences. Because land has a lower specific heat than water, the land heats up faster than water. The air over the land warms by conduction and rises due to its low density, creating an area of low pressure. The air over the water sinks because it is cooler and denser, and creates an area of high pressure. Because wind travels from areas of high pressure to areas of low pressure. The cooler air over the ocean pushes underneath the warmer air over the land, causing a sea breeze. The difference in pressure over the warm land and the cooler water result in a cool wind that blows from the sea onto the land, which equalizes the pressure.

Acid Precipitation

Acid precipitation is when sulfur dioxide and nitrogen oxides combine with moisture in the atmosphere and form precipitation that has a pH lower than that of normal rainwater. Acid precipitation includes acid rain, snow, and fog. It affects the chemistry of water in lakes and rivers. This can harm the organisms living in the water.

Altitude

Altitude is the distance above sea level, the average level of the surface of the oceans. Air pressure and density increases as altitude increases. In the troposphere, temperature decreases as altitude increases. In the stratosphere, temperature increases as altitude increases.

Water Vapor

Ancient Earth's atmosphere was thought to be water vapor with a little carbon dioxide (CO2) and nitrogen. Water vapor is water in the gaseous form. This ancient atmosphere didn't have enough oxygen to support life as we know it. As Earth and its atmosphere cooled, the water vapor cooled and condensed forming a liquid. Rain fell and then evaporated from Earth's surface repeatedly for thousands of years.

Radiation

Radiation is the transfer of energy by electromagnetic waves through space. Energy from the Sun travels to Earth through the process of radiation. Most of the energy from the Sun is visible light. At Earth's surface it is converted to thermal energy commonly called heat. As the Sun's energy passes through the atmosphere, some of it is absorbed by gases and particles, and some of it is reflected back into space. As a result, Earth's surface only receives and absorbs about 50% of incoming solar radiation.

Ozone Layer

The area of the stratosphere with high concentration of ozone is called the ozone layer. The presence of ozone layer causes increasing stratospheric temperatures with increasing altitude. An ozone (O3) molecule differs from an oxygen (O2) molecule. Ozone have three oxygen atoms instead of two. This difference is important because the ozone atom absorbs the Sun's ultraviolet rays more effectively than oxygen does.

Conduction

The transfer of thermal energy by particles that are touching. An example of conduction is touching a pot of water on a hot stove would transfer the energy from the pot to your hand. Conduction occurs where the atmosphere touches Earth.

Global Winds

Wind belts circle the Earth. The Sun is the source of the energy that causes the movement of air. Wind patterns can be global or local.

Land Breeze

Wind that blows from the land to a sea or lake due to local temperature and pressure differences.At night, the process that forms a sea breeze is reversed. At night, the land cools down faster than water does. The cooler, denser air over the land sinks, creating an area of high pressure. The warmer, less dense air over the water rises, creating an area of low pressure. Because wind travels from areas of high pressure to areas of low pressure. The cooler, denser air over the land pushes below the warmer air over the water causing a land breeze. The difference in pressure over the warm water and the cooler land result in a cool wind that blows from the land to the sea, which equalizes the pressure.