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What Causes the Weather?

What Causes the Weather?. Air Masses. Air Masses. Large Bodies of air (Can be 1000s of sq miles) Form over both land and water Over Land Air Masses are: Dry Warm in summer and cold in winter Over Water Air Masses are: Moist Relatively stable temperatures. Air Masses Move.

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What Causes the Weather?

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  1. What Causes the Weather?

  2. Air Masses

  3. Air Masses • Large Bodies of air (Can be 1000s of sq miles) • Form over both land and water • Over Land Air Masses are: • Dry • Warm in summer and cold in winter • Over Water Air Masses are: • Moist • Relatively stable temperatures

  4. Air Masses Move • Storms are caused when two different air masses make contact • This causes wind, rapid temperature change and precipitation • The line between two air masses is called a “front”

  5. Warm Front

  6. Warm Front • Occurs when a warm air mass moves into a cooler area • Warm air rises above the cooler air • This will cause precipitation and fog • Very common in the Spring (April showers bring May flowers)

  7. Cold Front

  8. Cold Front • Can move twice as fast as warm fronts • Cold air masses move to a warmer area • The cold air forces itself under the warmer air • As the warm air rises it cools quickly • Can cause severe weather such as thunderstorms

  9. Clouds • Formed when water vapour in the air cools and condenses (changes to liquid) • There are three main types • Cirrus • Cumulus • Stratus • These can combine to form other types

  10. Cirrus

  11. Cirrus Clouds • Form high in the atmosphere (10-15kms) • Very cold and made up of ice crystals • Formed when warm air is pushed very high upwards • Usually a result of a cold front and means bad weather is coming

  12. Cumulus Clouds

  13. Cumulus Clouds • Most familiar looking clouds • Approximately 500 meters above us • Made up of water droplets • Usually form when sunshine warms a pocket of air causing it to rise and condense • Usually a sign of fair weather

  14. Stratus Clouds

  15. Stratus Clouds • Very low level clouds • Sometimes touch the ground (fog) • Average 1km thick • Build when warm air rises slowly over cold air • Usually the result of a warm front

  16. Forecasting • The main goal in studying these systems is to accurately predict the weather • This is extremely difficult because • There are many variables (temp, currents, etc) • These variables can be unpredictable • Everything is connected

  17. El Nino • This occurs when the waters of the South Pacific become warmer • Usually every 3 to 7 years • This has drastic global consequences • Winds change direction • Brings heavy rains to deserts • Brings drought to farmland • Very unpredictable patterns

  18. Jet Streams • Very high altitude winds (9000-12000 m) • Very fast: more than 300km/h • These dictate the paths storms will follow • By using weather balloons we can identify the locations of jet streams and therefore predict the directions storms will go

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