Introduction to GCSE Weather


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for GCSE Geography Edexcel A

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Introduction to GCSE Weather

  1. 1. <ul><li>Learning Objectives </li></ul><ul><li>You will be able to describe the main variations of weather and climate around the world </li></ul><ul><li>You should be able to list the main factors that affect the variations in weather & climate </li></ul>
  2. 2. Key ideas for this section of the course <ul><li>Characteristics of Air masses </li></ul><ul><li>Relief and frontal rainfall </li></ul><ul><li>Sequences of low pressure systems </li></ul><ul><li>Stable Anticyclonic conditions (high pressure) </li></ul><ul><li>Use of synoptic charts </li></ul><ul><li>Characteristics of Maritime and Eastern continental climates </li></ul>
  3. 3. Low Pressure systems (Cyclones)
  4. 4. Low pressure systems – bring changeable weather
  5. 5. How they form: Warm moist air in the Atlantic is drawn polewards by the jet stream. As the warm air meets the cold air from the Pole the cold air undercuts the warm causing condensation and cloud formation.
  6. 9. <ul><li>Two different views of a depression NW of UK with an anticyclone to the SE </li></ul>
  7. 10. Depressions <ul><li>Depressions are large areas of low pressure in middle and high lattitudes </li></ul><ul><li>Most depressions move rapidly from west to east taking just 3 or 4 days to cross the Atlantic </li></ul><ul><li>Depressions bring mild and changeable weather, stormy periods of cloud and rain are followed by spells of bright sunny weather </li></ul><ul><li>The cloudy and wet conditions form along boundaries known as fronts </li></ul><ul><li>There are three types of front: warm, cold and occluded </li></ul><ul><li>Fronts separate warm air from cold air </li></ul><ul><li>Air rises along a front. As it rises air cools to form thick cloud and precipitation </li></ul>
  8. 11. <ul><li>Describe the weather through a depression </li></ul>
  9. 12. <ul><li>AS the depression moves east the low pressure air in the warm sector gets pushed up above the cold air. The gentle gradient of the warm front means cloud and rain affect large areas as the depression nears. </li></ul><ul><li>Air rushing into this low pressure zone create strong winds spiralling anti-clockwise into the centre. </li></ul><ul><li>Inside the warm sector conditions improve with cloud and rain being weaker and sun breaks out at times. </li></ul><ul><li>The cold front travels faster and with a steeper gradient undercuts the rear of the warmer air. This forces moist air into a rapid ascent leading to rapid condensation, cloud formation and heavy rainfall. </li></ul><ul><li>As the cold front passes pressure rises, temp falls, cloud begins to break up and precipitation dies away. </li></ul>
  10. 13. High Pressure systems (Anticyclones)
  11. 16. <ul><li>Areas of high pressure form over continental land masses </li></ul><ul><li>Bring spells of calm, dry and settled weather </li></ul><ul><li>In summer they bring warm, sunny conditions with temp above average </li></ul><ul><li>Winter anticyclones bring extreme cold weather and night-time frost </li></ul><ul><li>Air moves downwards towards the earths surface preventing thick cloud and heavy precipitation forming </li></ul><ul><li>Large high pressure over Europe can determine paths of depressions by deflecting them away from the UK </li></ul>Anticyclones
  12. 18. Summary <ul><li>Low pressure system and high pressure systems bring different weather </li></ul><ul><li>Low pressure systems bring changeable weather </li></ul><ul><li>High pressure systems bring stable weather </li></ul><ul><li>Low pressure systems bring strong winds and rain </li></ul><ul><li>High pressure systems bring clear skies </li></ul><ul><li>High pressure in summer – high daytime temperature </li></ul><ul><li>High pressure in winter – Cold crisp days, fog, freezing nights </li></ul>