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Weather Patterns

Weather Patterns. Most weather changes occur because of differences in the temperature or differences in air pressure Air pressure : pressure that the air exerts on the Earth, directed equally in all directions. Changes in the weather. Things affecting air pressure : temperature water vapor

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Weather Patterns

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  1. Weather Patterns

  2. Most weather changes occur because of differences in the temperature or differences in air pressure Air pressure: pressure that the air exerts on the Earth, directed equally in all directions Changes in the weather

  3. Things affecting air pressure: • temperature • water vapor • elevation Barometer:instrument used to measure air pressure (measured in millibars) Changes in the Weather

  4. The measure of air pressure is simply the measure of how much air is pressing down on a particular area Changes in the Weather

  5. Isobars: lines on a weather map that connect points with the same air pressure The closer the isobars the stronger the winds in that area. Weather Map Information

  6. Changes in air pressure create high and low pressure centers that have specific weather conditions. Changes in the Weather

  7. Low Pressure & High Pressure Centers Low Pressure Center -“cyclones” -pressure decreases toward center -winds blow inward and counterclockwise (N. Hemisphere) High Pressure Center -“anticyclones” -pressure increases toward center -winds blow outward and clockwise (N. Hemisphere)

  8. Low Pressure Center High Pressure Center Rising air is associated with cloud formation and precipitation. Sinking air produces clear skies.

  9. Air mass: a large body of air that has the same temperature and humidity throughout Changes in the Weather

  10. We are mostly affected by a maritime tropical (mT) air mass from the Atlantic ocean. -Brings mild, cloudy winters and hot humid summers with hurricanes and thunderstorms Changes in the Weather

  11. Front: boundary between two air masses having different temperatures and humidity - Fronts are named for the type of weather moving into a region. Changes in the Weather

  12. Cold air front: forms when cold, dense air moves into a region occupied by warmer air * brings strong storms (squall) with clear days following Types of Fronts

  13. Warm air front: forms when warm air moves into an area formerly covered by cooler air * Brings hot, humid days and precipitation over a large area Types of Fronts

  14. Stationary front: the flow of air on either side of the front is neither toward the cold air mass nor toward the warm air mass, but almost parallel to the line of the front- the surface position of the front does not move Types of Fronts

  15. Occluded front: two cold masses sandwich a warm mass * Brings strong winds and heavy rains Types of Fronts

  16. Weather Map Symbols

  17. Changes in air temperature especially along fronts can cause an increase in wind. Wind: movement of air Changes in the Weather

  18. Factors that affect wind • Changes from high pressure to low pressure • Changes in temperature due to unequal solar radiation Changes in the Weather

  19. Factors that control wind • Air pressure • Friction • Corioliseffect Coriolis effect: deflection of wind and ocean currents caused by the Earth’s rotation Changes in the Weather

  20. anemometer: instrument that measures wind speed Wind vane: measures wind direction Weather Map Information

  21. Information about wind speed and direction on a weather map is often shown using wind barbs like shown below. Weather Map Information

  22. Polar easterlies: cold, but weak winds between 50°and 60°. These winds are not constant. Westerlies: belt of very strong winds between 40°and 60°. Trade winds: warm, steady winds between 0°and 30o Doldrums: calm, surface winds at the equator Types of Global Winds

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