Sponsored Links
This presentation is the property of its rightful owner.
1 / 34

Atmosphere PowerPoint PPT Presentation

  • Uploaded on
  • Presentation posted in: General

Atmosphere. 78% nitrogen, 21% oxygen. Water Vapor. up to 4% by volume leaves atmosphere as dew, rain or snow. Density of Air. Warm air is less dense than cold air Humid air is less dense than dry air. Air Movement. Air near sea level is packed by pressure As air rises - expands and cools

Download Presentation


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


  • 78% nitrogen, 21% oxygen

Water Vapor

  • up to 4% by volume

  • leaves atmosphere as dew, rain or snow

Density of Air

  • Warm air is less dense than cold air

  • Humid air is less dense than dry air

Air Movement

  • Air near sea level is packed by pressure

  • As air rises - expands and cools

  • As air descends- compresses and warms

Fig 7-1a, p.133

Fig 7-4, p.135

Fig 7-2b, p.134

Fig. 7-2b, p. 134

Fig. 7-2a, p. 134

Fig 7-3b, p.135


  • Warm air can hold more water vapor than cool air

  • As air rises, it cools and water vapor may condense into clouds and eventually precipitation

Atmospheric Circulation

  • Wind = mass movement of air

  • wind patterns caused by variations in solar heating and earth’s rotation

Uneven Solar Heating & Atmospheric Circulation

  • Air is warmed in the tropics and rises

  • Air is cooled near the poles and falls

Earths air

Circulation if




Fig. 7-5, p. 136



  • …putting all of this together…the hot, humid, air over the tropics is LESS dense (than all other air masses); this means:

    (a) Less dense air rises (like a hot air balloon);

    (b) As it rises (vertical) the pressure decreases;

    (c) As pressure decreases, air EXPANDS;

    (d) As it expands, it COOLS

    …then the reverse again…+ horizontal (wind) movement

Fig 7-1a, p.133


…When you add the horizontal (wind) movement it pushes this (originating hot, dry, tropical air) BOTH up and out (North/South) for distribution throughout the entire atmosphere. How?



Tropical air rises, meets density around it (more dense than that above it but less dense than that below it) so it can’t “move” vertically …but it must go somewhere!

SIDEWAYS! (joins Atmospheric Circ. pattern, moving horizontally, toward POLES) & as it rises poleward it COOLS, gets more dense, and falls back (toward equator) again…and again…

Influence of the rotation of the earth…

Coriolis Effect

  • The eastward rotation of the earth deflects any moving object away from its initial course

  • the deflection is clockwise in the Northern hemisphere

  • the deflection is counterclockwise in the Southern hemisphere

Coriolis Deflection

  • “The apparent deflection of objects moving across Earth’s surface to the right of direction of travel in the Northern Hemisphere and to the left in the Southern Hemisphere.”

  • Different because of difference of speed and width of Earth @ equator vs. poles

  • Increases poleward & as speed increases.

Fig 7-6, p.136

Fig 7-7, p.137

Fig 7-8, p.137

Fig 7-9, p.138

Wind Patterns

  • At bands between cells air is moving vertically

  • winds are weak and erratic

  • doldrums or intertropical convergence zone (ITCZ) at equator

    • ascending air

  • Subtropical high pressure belt at 30o

    • descending air, very dry

Wind Patterns

  • Within cells air moves horizontally from high to low pressure areas

  • produces strong dependable winds

    • Trade winds or easterlies

    • westerlies

    • polar easterlies


Global Wind Circulation

Global Wind Circulation


  • Movement of air across a pressure gradient parallel to Earth’s surface is called a wind.

  • Winds are designated according to the direction from which they come.

  • In contrast, ocean currents are designated according to the direction towards which they travel.

  • Login