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Chapter 17 Section 1 What is Weather?

Chapter 17 Section 1 What is Weather?. the state of the atmosphere at a specific time and place describes air pressure, wind, temperature, and moisture in air. 1. weather. 2. How is heat given out on Earth?. - air and water currents. 3. What do heat and Earth’s air and water cause?.

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Chapter 17 Section 1 What is Weather?

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  1. Chapter 17 Section 1 What is Weather?

  2. the state of the atmosphere at a specific time and place • describes air pressure, wind, temperature, and moisture in air 1. weather 2. How is heat given out on Earth? - air and water currents 3. What do heat and Earth’s air and water cause? • weather • sun is energy that makes wind and moves weather

  3. a measure of the average amount of motion of molecules • air moving quickly = warm • air moving slowly = cold 4. temperature 5. wind • air moving in a specific direction • results from air moving from high pressure (cool) to low pressure (warm) • wind vane- arrow points in direction of wind • wind sock- sock points toward blowing wind • anemometer- measures speed with rotating cups 6. How are wind speed and direction measured?

  4. - amount of water vapor present in the air 7. humidity 8. Why can more water vapor be present in warm air than in cold air? • warm air- molecules move fast and water molecules can’t come together • cold air- molecules move slow, for liquid water and air is saturated 9. relative humidity - measure of amount of water vapor present in the air compared to the amount needed for saturation at a specific temperature

  5. temperature at which air is saturated and condensation forms • changes with amount of water vapor in the air 10. dew point pg. 473 Applying Math- Dew Point

  6. 1. How do clouds form? • by warm moist air being forced upward, expanding, and cooling • water vapor condenses into tiny droplets and remain hanging in the air 2. How are clouds classified? • by shape and height • vary with temperature, pressure, and amount of water vapor in the atmosphere • stratus • cumulus • cirrus 3. 3 main cloud types

  7. layers, smooth even sheets • form at low altitudes • fair weather, rain, or snow 4. stratus clouds • a stratus cloud • formed when air is cooled to its dew point near the ground 5. fog 6. cumulus clouds • puffy, often with flat bases • very high • fair weather or thunderstorms

  8. fibrous or curly • high, thin, feathery • made of ice crystals • fair weather, can indicate approaching storms 7. cirrus clouds • describe height of cloud base • cirro = high • alto = middle • strato= low 8. cloud prefixes • “dark rain cloud” • added to other names • ex. cumulonimbus= thunderstorm 9. What does nimbus mean?

  9. 1. Steps in cloud formation warm air is forced upward air expands and cools at higher temperature relative humidity reaches 100% water vapor condenses water droplets form a cloud

  10. 2. precipitation - water falling from clouds 3. What factors affect the size of raindrops? • strong updrafts in a cloud = large drops • rate of evaporation = dry, may never reach Earth 4. 4 main types of precipitation • rain - sleet • snow - hail

  11. 5. What determines the type of precipitation? • air temperature 6. rain • water droplets fall from the sky • temperatures are above freezing (32°F or 0°C)

  12. water vapor changes directly into a solid in the atmosphere (sublimation) • 32°F or 0°C or below for snow 7. snow

  13. 8. sleet -rain passes through a layer of freezing air near Earth’s surface

  14. lumps of ice • forms in cumulonimbus clouds • water freezes in layers around nucleus of ice • usually smaller than 2.5 cm, can be size of softballs 9. hail

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