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DO NOW

DO NOW. Tell a friend what you feel like on humid days. What time of year do we have humid days?. Chapter 2: “Understanding Weather”. Humidity. Humidity – the amount of water vapor in air Air’s ability to hold water vapor changes as the temperature of the air changes.

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DO NOW

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  1. DO NOW Tell a friend what you feel like on humid days. What time of year do we have humid days?

  2. Chapter 2: “Understanding Weather”

  3. Humidity Humidity – the amount of water vapor in air • Air’s ability to hold water vapor changes as the temperature of the air changes. • Increased temperature means the air can hold more water. • Decreased temperature means the air can hold less water.

  4. Relative Humidity • Relative Humidity –ratio of water vapor in the air to the maximum amount the air can hold 2 factors that affect relative humidity: Temperature Water vapor in the air

  5. Measuring Relative Humidity • How to measure relative humidity? • Psychrometer – a tool to measure relative humidity; contains a wet and a dry bulb. • 1) Wet-bulb thermometer –bulb covered with wet cloth • 2) Dry-bulb thermometer –bulb is dry • The difference in temperature readings between the 2 thermometersis used to determine the relative humidity.

  6. Determining Relative Humidity

  7. Water in the Air • Dew Point –temperature when the air can no longer hold any more water (gas condenses to a liquid) • Happens when relative humidity reaches 100%

  8. DO NOW Write the answer to this question in the DO NOW section of your binder: • What is the relative humidity if the temperature in the classroom today is 20oC on the dry bulb and 17oC on the wet bulb?

  9. Clouds • Clouds are groups of millions of tiny water droplets or ice crystals • 2 Steps to Cloud formation: • Air rises • Air cools below the dew point, water droplets form

  10. Clouds Are Made Of… Ice crystals – form when water condenses below 0 C o Water droplets – form when water condenses above 0 C o

  11. Clouds Clouds are classified by: 1) Altitude • Low clouds • Middle clouds • High clouds • *NIMBO or NIMBUS = clouds producing precipitation* • 2) Shape: • Stratus clouds (sheets, stripes, bands) • Cumulus clouds (clumpy & puffy) • Cirrus clouds

  12. Low Clouds • Found below 2,000 meters & made of onlywater droplets • Three Types: • Stratus Clouds • Nimbostratus Clouds • Stratocumulus Clouds

  13. “Overcast” • Ill-defined edges • In layers • Block sun

  14. Dark stratus cloud • continuous rain • Gray, rainy days

  15. Lumpy & Low lying • Patches of clouds with some blue between. • Flat (Doesn’t look like popcorn)

  16. Middle Clouds • Found between 2,000 meters and 6,000meters • They are made of water droplets or ice crystals • Alto- means “middle” • Four Types: • Cumulus • Cumulonimbus • Altocumulus • Altostratus

  17. White & Puffy • Distinct edges • popcorn-like; NOT flat

  18. anvil shaped top • Big & Dark cumulus cloud • Thunderstorm clouds • Hail, tornadoes • Tallest clouds

  19. Layered cumulus clouds • Distinct cloud elements • Patchy, scattered, or in bands

  20. Uniform & Scattered Coverage • Difficult to detect individual features

  21. High Clouds • Found above 6,000 m • Temperature are very cold and made of icecrystals Cirro- means “high” Three Types: • Cirrus Clouds • Cirrocumulus Clouds • Cirrostratus Clouds

  22. Thin & feathery, wispy

  23. Thick white wispy • Distinct patchy or wavelike appearance

  24. . • Sheet-like & cover entire sky • Usually transparent • (sun/moon can easily be seen)

  25. #1 #2 #3 #4 #5 #6 #7 #9 #8 #10

  26. #5 #2 #1 #3 #4 #6 #8 #7

  27. 8 10 9 5 7 6 4 3 2 1

  28. Recap!!! What is weather? What does it greatly depend on? Weather is the condition of the atmosphere at a certain time and place. It depends greatly on the amount of water in the air. What is the difference between humidity and relative humidity? Humidity is the amount of water vapor in the air. Relative humidity is the ratio of the amount of water vapor in the air to the maximum amount the air can hold.

  29. A Stratus B Cumulus Which two main cloud shapes are seen in this picture?

  30. C Cirrus D Cumulus Which two main cloud shapes are seen in this picture?

  31. Cirrus Clouds Stratus Clouds

  32. Recap!!! What does nimbo or nimbus mean for clouds? It produces precipitation What does stratus mean for clouds? They are layered What are each of the following clouds made of? 1) Low Clouds 2) Middle Clouds 3) High Clouds 1) Water droplets only 2) Water droplets/ice crystals 3) Ice crystals only What are the two most common forms of precipitation? Rain and snow

  33. Air Masses • Air Masses – a very large volume of air that has a certain temperature & moisture content

  34. Front– the place where two or more air masses meet • When air masses meet, the less dense air mass rises over more dense air mass. • Since warm air is less dense, warm air masses usually rise above cold air masses

  35. Fronts • The four main kinds of fronts are: • 1) Cold Fronts • 2) Warm Fronts • 3) Occluded Fronts • 4) Stationary Fronts

  36. Cold Fronts • Cold air mass moves undera warm air mass and pushes the air up • Cold air mass replaces warm air mass • Moves quick & brings heavy precipitation

  37. Warm Fronts • Warm air mass moves in over a cold air mass leaving an area. • Warm air mass replaces cold air as it moves away • Bring light rain & followed by clear, warm weather

  38. Cold air mass pushes Warm air mass replaces warm air mass away a cold air mass Visual

  39. Occluded Fronts • Warmair mass is caught between 2 cold air masses. • Brings cool temperatures, rain, and snow

  40. Stationary Fronts • Cold air mass & a warm air mass move toward each other. • Neither has enough energy to push the other away. • Remain in same place causing cloudy weather

  41. Occluded Front = warm air mass is trapped between two cold air masses, which move together and push warm air away • Stationary Front = air masses stay in one place

  42. Air Pressure and Weather • Cyclone– air mass formed that has lower pressure than surrounding air. • Air rises and cools • Forecast: Clouds can form & cause rainy or stormy weather • Anticyclone – air mass that has higher pressure than the surrounding air • Air sinks and gets warmer • Relative humidity decreases • Forecast: Warm sinking air brings dry, clear weather

  43. Cyclones and anticyclones can affect each other. Air moving out from anticyclones move towards areas of low pressure. This movement can form a cyclone.

  44. Recap!!! • What does air mass depend on? Water Content (Moisture) & Temperature • What are the four different kinds of fronts? Cold Fronts Warm Fronts Occluded Fronts Stationary Fronts

  45. Recap!!! • What is the difference between Cyclones and Anticyclones? • Cyclones  lower pressure than surrounding air • Cools as it rises. • Anticyclones  higher pressure than surrounding air • Warms as it sinks. • How are front and air masses related? • A front is where two or more air masses meet. • Therefore, without air masses…there would be no • fronts.

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