Ascending / Descending air

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Ascending / Descending air

  1. 1. Ascending/Descending
  2. 2. Air masses <ul><li>Air mass – large body of air whose temp, pressure, and humidity is uniform. </li></ul><ul><li>Front – boundary between 2 air masses </li></ul><ul><li>Warm front – has warm air behind it </li></ul><ul><li>Cold front – has cold air behind it </li></ul>
  3. 3. <ul><li>Warm air absorbs and holds water vapour </li></ul><ul><li>Cold air cannot hold moisture so forms condensation -> cloud-> precipitation </li></ul>
  4. 4. How depressions form <ul><li>Warm air meets cold air </li></ul><ul><li>Warm air dents into cold air </li></ul><ul><li>Cold air swirls + surrounds warm air </li></ul><ul><li>12 – 24 hrs -> Depression </li></ul><ul><li>Depressions move eastwards over Ireland and bring variable / wet weather conditions </li></ul>
  5. 5. Ascending Descending Low Pressure High Pressure Depression / Cyclone / Lows Anticyclone / Highs Oval / lowest at centre Oval / large / highest at centre Strong winds Light winds Close isobars Wide isobars Blow to centre (anticlockwise) Blow away from centre (clockwise) Lots cloud Clear skies Lots rain Dry weather
  6. 6. Depression - Anticyclone
  7. 7. Cycle of a depression <ul><li>Cold air </li></ul><ul><li>Rain </li></ul><ul><li>Warm air </li></ul><ul><li>Rain </li></ul><ul><li>Cold air </li></ul>
  8. 8. http://www.classzone.com/books/earth_science/terc/content/visualizations/es2002/es2002page01.cfm?chapter_no=visualization (animation) http://www.school-portal.co.uk/GroupDownloadFile.asp?File=39951
  9. 9. Can you identify the cold air mass in this satelite photo? This is what these fronts would look like on a weather map on TV.
  10. 10. Remember…. <ul><li>The closer the isobars the stronger the winds </li></ul><ul><li>The further apart the isobars the gentler the winds </li></ul>
  11. 11. Irish depressions <ul><li>Polar air cold, dry (Polar Winds) </li></ul><ul><li>Polar Front Mid latitudes </li></ul><ul><li>Tropical air warm, damp (S Westerlies) </li></ul>
  12. 12. <ul><li>http://www.juicygeography.co.uk/downloads/flash/highpressure.swf high pressure animation </li></ul><ul><li>http://www.juicygeography.co.uk/downloads/flash/lowpressure.swf low pressure animation </li></ul>

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