The Atmosphere Part 1 of 2

Chapter Overview  Lesson 1: The Atmosphere  Lesson 2: Weather Elements  Lesson 3: Aviation Weather  Lesson 4: Weather Forecasting  Lesson 5: The Effects of Weather on Aircraft Aircraft Chapter 2, Lesson 1

Lesson Overview  Atmospheric regions  Roles of water and particulate matter  Primary causes of atmospheric motion  Identify types of clouds  How atmospheric layers impact flight Chapter 2, Lesson 1

Atmospheric Regions  Four or five depending on your source material  Some consider Exosphere as fifth region extending into space  4 regions extend more than 350 miles from surface Chapter 2, Lesson 1 Reproduced from US Department of Transportation/Federal Aviation Administration

Atmospheric Regions Chapter 2, Lesson 1 Reproduced from US Department of Transportation/Federal Aviation Administration  The atmosphere contains the whole mass of air surrounding the Earth  Made up of a mixture of gases: 78% Nitrogen (N 2 ) 1% Mixture of other gases (CO 2, pollutants, etc. 21% Oxygen (O 2 )  Atmosphere protects us from high-energy radiation and the frigid vacuum of space  Absorbs energy from the Sun, recycles water and other chemicals, and works with the electrical and magnetic forces to provide a moderate temperature

Troposphere Chapter 2, Lesson 1 Reproduced from US Department of Transportation/Federal Aviation Administration  Lowest, densest part of Earth’s atmosphere in which most weather occurs  Starts at Earth’s surface and extends up to 9 miles  Up to 4 miles at poles and 9 miles at equator  Tropopause is the boundary layer separating the troposphere and the stratosphere  Tropopause and troposphere known as the lower atmosphere

Stratosphere Chapter 2, Lesson 1 Reproduced from US Department of Transportation/Federal Aviation Administration  Extends about 30 miles above Earth’s surface  Very dry and less dense compared to troposphere  Temperature begins to rise again to about 26.6 ⁰ due to ozone layer contained in stratosphere  Ozone absorbs Sun’s UV radiation, allowing life to exist on land  Stratopause is the boundary layer separating the stratosphere and mesosphere

Mesosphere Chapter 2, Lesson 1 Courtesy of NASA  Extends up to 53 miles above Earth’s surface  Coldest layer – near top of mesosphere, temps dip to as low as -93 o C (-135 o F)  Chemicals exist in an excited state by absorbing energy from Sun  Mesopause separates mesosphere from thermospere  Mesosphere and stratosphere form middle atmosphere

Thermosphere Thermosphere —Exosphere  Extends about 350 miles above Earth’s surface  Considered the “hottest” layer as it absorbs direct energy from the sun first  Chemical reactions occur faster here than on Earth’s surface  Molecular temps can reach over 3000⁰ F  But actual energy per volume is low since thermosphere is practically a vacuum  Most satellites and spacecraft orbit in this layer  Thermopause is the boundary layer with exosphere Chapter 2, Lesson 1

Roles of Water and Particulate Matter Chapter 2, Lesson 1

Roles of Water and Particulate Matter Chapter 2, Lesson 1  The water content of the atmosphere is almost entirely restricted to the troposphere. Occasionally, a thunderstorm will produce enough energy to thrust part of its top into the stratosphere. Water may also be injected into the stratosphere by the engines of high-flying aircraft.

Roles of Water and Particulate Matter Chapter 2, Lesson 1  In the troposphere, water goes through a cycle from water vapor to condensation to precipitation  As it goes through this cycle, it takes on several forms. Liquid Solid Condensation

 Evaporation: liquid to gaseous  Sublimation: solid to gaseous without first going through liquid state  Condensation: gaseous to liquid  Deposition: gaseous to solid without first going through liquid state  Melting: solid to liquid  Freezing: liquid to solid Chapter 2, Lesson 1 Roles of Water and Particulate Matter

Evaporation Chapter 2, Lesson 1 Courtesy of NOAA/Historic NWS Collection  The process by which liquid water molecules change to a gas or vapor state and enter the atmosphere  Evaporation requires heat  86% of evaporation occurs from solar radiation heating the oceans creating water vapor  Clouds form when air is saturated with water vapor  Temperature and pressure are the primary cause of water vapor in the air condensing into liquid (forming clouds) then falling to Earth

Sublimation  Ever notice how old ice cubes in the freezer become smaller and deformed?  Ever notice how a snowbank seems to get smaller or disappear even though temps were below freezing?  Sublimation occurs in below freezing temps  Intense sunlight with strong winds can transform snow and ice into water vapor without first melting Chapter 2, Lesson 1 Courtesy of NASA/Goddard/Sarah DeWitt

Humidity and Relative Humidity  Humidity (or absolute humidity) is the actual amount of water vapor in air at a given time  The amount of water vapor the air is able to hold depends on the temperature  Higher temps => hold more water vapor  Relative humidity - Amount of water vapor that can still enter the air mass before it becomes saturated  Expressed as ratio of the absolute humidity to the maximum amount of water vapor that air could hold at that given temperature and pressure Chapter 2, Lesson 1

Humidity and Relative Humidity Chapter 2, Lesson 1

Condensation and Precipitation Chapter 2, Lesson 1 Courtesy of NASA/Ben Smegelsky  When air become saturated, any more water vapor added will return to a liquid or solid form  Seen as either condensation and/or precipitation  If a cloud’s droplets grow until the buoyancy of the air and any existing updrafts will not support them, they fall as precipitation

Condensation and Precipitation Chapter 2, Lesson 1 Courtesy of NASA/Ben Smegelsky If the water vapors that fall are not visible, it is condensation

Dew Point  Temperature at or below which water vapor in air will condense  Determined by the amount of moisture in the air and the air temperature  Does not indicate the type of condensation, only that some type of condensation will take place at the dew point  Could be fog, dew, frost, clouds, rain, hail, snow, etc Chapter 2, Lesson 1 Courtesy of NASA/Ben Smegelsky

Particulate Matter  Dust, pollution and other small particles play an important role in the water cycle  Without suspended particles in the atmosphere, certain forms of condensation and precipitation would not exist  These particles serve as condensation nuclei for water vapor when the temp is right  This is how cloud droplets form Chapter 2, Lesson 1 Courtesy of Sean Waugh NOAA/NSSL

Primary Causes of Atmospheric Motion  Heat causes air to circulate around Earth’s surface  Rising warm air and heavy, sinking cool air results in atmosphere’s circular motion  Tilted axis also affects atmospheric circulation Chapter 2, Lesson 1 Modified from US Department of Transportation/Federal Aviation Administration.

Coriolis Force  How Earth’s rotation affects the motion of air  Deflects air to the right in Northern Hemisphere and left in Southern Hemisphere  Breaks up flow of air into three cells at different latitudes in each hemisphere Chapter 2, Lesson 1 Reproduced from US Department of Transportation/Federal Aviation Administration

Chapter 2, Lesson 1 Reproduced from US Department of Transportation/Federal Aviation Administration The Atmosphere Part 1 of 2 Done….. next….Part 2 of 2