Geography Notes

Geography Notes

February 25, 2013

Winds Aloft
  * Isobaric surfaces slope downward from the low latitudes to the pole
  * Atmosphere is warmer near the Equator, pressure gradients force pushes air poleward
  * Pressure gradient force increase with altitude, bringing strong winds at high altitudes
  * Friction increases from low latitude to high latitude
  * Decreases in upper atmosphere where wind speeds are high

The Geostrophic Wind
  * At high latitudes, a moving parcel of air is subjected to: Pressure gradient force and Coriolis forces.
  * When forces balance, air moves at right angles to the pressure gradient, parallel to the isobars, as the geostrophic wind
  * Winds that move bulk of our air mass around the planet
  * Heavy lifting of moving heat

Global Circulation at Upper Levels
  * General pattern global circulation at upper levels
      * Bands of equatorial easterly winds (result of downward air)
        * Bring air into the equator
        * Found at higher latitudes
      * Tropical high-pressure belts
      * Zone of westerly winds – come from est and blow to east
      * Polar lows
      * Lack of land mass and lack of friction fast winds speeds in southern hemisphere

Jet Streams and the Polar Front
  * Jet streams are streams of fast-moving air at high altitudes that occur where atmospheric temperature gradients are strong
  * Each hemisphere normally exhibits westerly polar and subtropical jet streams.
  * An easterly jet occurs in summer over Asia and Africa
  * Polar jet located between 35 and 65 latitude in both hemispheres
  * Boundary between cold polar air and warm subtropical air
  * Altitudes of 10 to 12 km (about 30,000 to 40,000 ft)

Disturbances in the Jet Stream
  * Broad wavelike undulations called Jetstream disturbances or Rossby waves
  * Occurs from heating and cooling
  * The flow of air along the polar front is fairly smooth, but then it begins to undulate
  * Undulation becomes...

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