Atmosphere

Atmosphere

1. Section 3: Layers of the Atmosphere

   • Scientists divide Earth's atmosphere into four main layers classified according to changes in temperature. These layers are the troposphere, the stratosphere, the mesosphere, and the thermosphere.
   • The Troposphere
     • The troposphere is the inner, or lowest, layer of the atmosphere and where all weather occurs. 16 kilometers above the equator to 9 kilometers at the South and North poles.
   • The Stratosphere
     • The stratosphere extends from the top of the troposphere to about 50 kilometer above the surface. It is the second layer of the atmosphere and contains the ozone layer.
   • The Mesosphere
     • Above the stratosphere a drop in temperature indicates the mesosphere, the layer that protects Earth from being hit by meteoroids.
   • The Thermosphere
     • The thermosphere, the outermost layer, extends from 80 kilometers above the surface outward into space. It is very hot even though the air is thin because the molecules move rapidly, creating heat. It is divided into two sections, the ionosphere and the exosphere. The ionosphere is the lower layer, this is where the auroras occur. The exosphere is the outermost layer and extends from about 400 kilometers outward for thousands of miles.

2. Section 4: Energy in Earth's Atmosphere

   • Energy from the Sun
     • Electromagnetic waves is a form of energy that can travel through the vacuum of space. Radiation is the direct transfer of energy by electromagnetic waves given off from the sun.
     • Visible Light
       • Visible light includes every color of the rainbow which are the result of different wavelengths.
     • Non-Visible Radiation
       • One form of electromagnetic energy, infrared radiation, has wavelengths that are longer than red light. Ultraviolet radiation gives off wavelengths that are shorter than violet light.
   • Energy in the Atmosphere
     • Some sunlight is absorbed or reflected by the atmosphere before it can reach the surface. The rest passes through the atmosphere  to the surface. Dust particles and gases in the atmosphere reflect light in all direction, a process called scattering.
   • Energy at the Earth's Surface
     • When Earth's surface is heated, it radiates most of the energy back into the atmosphere as infrared radiation. The process by which gases hold heat in the air is called the greenhouse effect.

3. Section 1: The Air Around You

   • Weather is the condition of Earth's atmosphere at a particular time and place. Earth's atmosphere is the envelope of gases that surrounds the planet.
   • Composition of the Atmosphere
     • Earth's atmosphere is made up of nitrogen, oxygen, carbon dioxide, water vapor, and many other gases, as well as particles of liquids and solids.
     • Nitrogen
       • Nitrogen is the most common gas in the atmosphere and makes up 3/4 of the air we breathe.
     • Oxygen
       • Oxygen is the second most common gas in the atmosphere even though it only makes up less than 1/4 of the volume.
     • Carbon Dioxide
       • "Each molecule of carbon dioxide is made of one atom of carbon and two atoms of oxygen. It is created when fuels are burned.
     • Other Gases
       • The one percent left is made mostly of argon and carbon dioxide.
     • Water Vapor
       • Water vapor is water in the form of gas. Water vapor molecules are made of two atoms of hydrogen and one atom of oxygen.
     • Particles
       • The air we breathe has tiny solid and liquid particles of dust, smoke, salt, and other chemicals. Pure air exists only in laboratories.
   • Importance of the Atmosphere
     • Earth's atmosphere makes conditions sustainable for life forms and without it no life could survive.
   • Air Quality
     • Pollutants are harmful substances in the air, water, or soil.
     • Sources of Pollution
       • Some pollution can be caused by natural actions such as forest fires, soil erosion, and dust storms. But most air pollution comes from the burning of fossil fuels.
     • Smog and Acid Rain
       • The burning of fossil fuels can cause smog and acid rain. Photochemical smog is the brown haze that develops in sunny cities. Acid rain is rain that contains more acid that normal.
   • Improving Air Quality
     • In the U.S. federal and state governments have passed laws to help decrease air pollution.

4. Section 6: Winds

   • What is Wind?
     • Wind is the horizontal movement of air from a high pressure area to a lower air pressure area. Winds are caused by differences in air pressure. Most differences in air pressure are caused by unequal heating of the surface.
     • Measuring Wind
       • An anemometer measures wind speed using three or four cups that spin on an axle. The force of the wind blows the cups around on the axle.
     • Wind-Chill Factor
       • The wind blowing over your skin removes body heat. The increased cooling a wind can cause is called the wind-chill factor.
   • Local Winds
     • Local winds are winds that blow over short distances. Local winds are caused by the unequal heating of the Earth's surface within a small area.
     • Land Breeze
       • A land breeze is the flow of air from land to a body of water.
     • Sea Breeze
       • A sea breeze of a lake breeze is a local wind that blows that blows from an ocean or lake.
   • Global Winds
     • Global winds are winds that blow steadily from specific directions over long distances.
     • Global Convection Currents
       • Temperature differences between the the equator and the poles produce giant convection currents in the atmosphere.
     • The Coriolis Effect
       • The way Earth's rotation makes winds curve is called the Coriolis effect.
   • Global Wind Belts
     • The major global wind belts are the trade winds, the polar easterlies, and the prevailing westerlies.
     • Doldrums
       • Warm air rises and the cool air moves in but quickly warms up before moving very far creating little or no wind.
     • Horse Latitiudes
       • Latitude is distance from the equator, measured in degrees. At about 30 degrees north and south, the air stops moving and sinks.
     • Trade Winds
       • In the Northern Hemisphere between 30 degrees north and the equator the wind generally blow northeast. In the Southern Hemisphere between 30 degrees south and the equator the wind generally blows southeast.
     • Prevailing Westerlies
       • In the mid-latitudes, between 30 degrees and 60 degrees north and south, winds that blow toward the poles are turned toward the east by the Coriolis effect. They play an important part in the weather of the United States.
     • Polar Easterlies
       • The Coriolis effect curves polar winds west producing polar easterlies. The polar easterlies meet the prevailing westerlies at about 60 degrees north and south latitudes, along a region called the polar front. This is an important cause of the weather in the U.S.
     • Jet Streams
       • Jet streams are bands of high-speed winds.

5. Section 2: Air Pressure

   • Properties of AIr
     • Because air has mass, it also has other properties, including density and pressure.
     • Pressure
       • Pressure is the force pushing on an area or surface. Air pressure is the result of the weight of a column of air pushing down on an area.
     • Density
       • Density is the amount of mass in a given volume. More molecules means the greater the density, less molecule means a lower density.
   • Measuring Air Pressure
     • A barometer is an instrument that is used to measure air pressure.
     • Mercury Barometers
       • A mercury barometer consists of a glass tube open at the bottom end and partially filled with mercury. AS air pressure increases the mercury becomes higher.
     • Aneroid Barometers
       • An eroid barometer has an airtight metal chamber that is sensitive to changes in air pressure.
     • Units of Air Pressure
       • Most meteorologists use inches of mercury to measure air pressure.
   • Altitude and the Properties of Air
     • Altitude is the distance above sea level.
     • Altitude Affects Air Pressure
       • Sea-level air has the weight of the whole atmosphere pressing on it therefore it has a greater air pressure than on a mountain.
     • Altitude Also Affects Density
       • As you go higher into the atmosphere the density decreases.

6. Section 5: Heat Transfer in the Atmospher

   • Thermal Energy and Temperature
     • Thermal energy is the total energy of motion in the particles of a substance.
     • Measuring Temperature
       • Air temperature is usually measured with a thermometer. A thermometer  is a thin glass tube with a bulb on one end that contains a liquid, usually colored alcohol.
     • Temperature Scales
       • Temperature is measured in two types of degrees, Celsius and Fahrenheit. 1 degree Fahrenheit equals 9.5 Celsius.
   • How Heat is Transferred
     • Recall that heat is the transfer of thermal energy from a hotter object to a cooler one. Heat is transferred in three ways within the atmosphere: radiation, conduction, and convection.
     • Radiation
       • Radiation is the energy coming directly from the sun through electromagnetic waves.
     • Conduction
       • Conduction is the direct transfer of heat from one substance to another that is touching.
     • Convection
       • Convection is the transfer of heat by the movement of a fluid.
     • Heating the Troposphere
       • Radiation, conduction, and convection all work together to heat the troposphere. Within the troposphere, heat is transferred mostly by convection. Convection currents is the rising of warm air and sinking of cold air.