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Weather

Weather. Air Pressure : wind, effect of altitude Air Temperature : atmospheric layers weather fronts cloud formation Other : heat transfer humidity instruments hurricanes!!. Sun = Engine of Weather. “Weather for Dummies” by John D. Cox. 100% Radiation ENERGY from Sun. 30%

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Weather

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  1. Weather • Air Pressure: • wind,effect of altitude • Air Temperature: • atmospheric layers • weather fronts • cloud formation • Other: • heat transfer • humidity • instruments • hurricanes!!

  2. Sun = Engine of Weather “Weather for Dummies” by John D. Cox 100% Radiation ENERGY from Sun 30% Reflected & Scattered 19% Absorbed by Atmosphere 51% Absorbed at Surface UNEVEN heating causes temperature & pressure differences.

  3. Weather & Wind • Weather is caused by the differences in temperature or pressure in the atmosphere. What is the usual pressure of the atmosphere at sea level in units of atm (atmospheres)? Click in number. What is this pressure in units of psi (pounds per square inch)? Why do you think wind occurs?

  4. Pressure and Altitude (review) In the mile-high city of Denver, visitors notice that it is harder to breathe when jogging because the air is “thinner” than at sea level. This indicates that: (a) the air pressure at high altitudes is lower than at sea level. (b) the air pressure at high altitudes is higher than at sea level. Higher “altitude” Lower “altitude” Gravity Added

  5. Air Pressure vs. Altitude 0.001 atm 50 km 0.1 atm Airplanes fly 12 km 1 atm Sea level 0 km • Air pressure decreases with increasing altitude! • 1 atm = 1 kg per cm2 area (= 1 L H2O on the end of your pinkie!)

  6. Pressure:Low Pressure Air Rises & High Pressure Air Sinks • If the air temperature is the same, then lower pressure air is less dense than higher pressure air. • Lower Pressure Air RISES - less dense air is more ‘buoyant’ and rises • Leads to cloudy weather (we’ll see why soon) • Higher Pressure Air SINKS - more dense air is less buoyant and sinks • Leads to clear weather

  7. Temperature and Atmospheric Layers Exosphere: 500+ km Thermosphere 80-500 km Mesosphere 50-80 km Stratosphere10-50 km OZONE heats up! Troposphere0-10 km Temperature (°C)

  8. Atmospheric Layers Match the descriptions to the appropriate atmospheric layers. (1) thermosphere (2) mesophere (3) stratosphere (4) troposphere > Atmospheric layer where the temperature decreases to about -90C at its highest altitude of about 80 km. > Located from ground level to about 10 km and temperature decreases with altitude. > Located from about 80 to 500 km and temperature increases with altitude. ______________________ > Atmospheric layer where ozone absorbs ultraviolet radiation from the sun. > Atmospheric layer where weather primarily occurs. > Located from about 50 to 80 km and temperature decreases with altitude. > Located from about 10 to 50 km and temperature increases with altitude.

  9. Temperature: Hot Air Rises and Cold Air Sinks • If the air pressure is the same, then hot air is less dense than cold air. • Hot air: fewer molecules hitting the walls with faster speeds • Cold air: more molecules hitting the walls with slower speeds • HOT AIR RISES - less dense air is more ‘buoyant’ and rises • After rising, hot air starts to cool! Why? • If there is water vapor in the air, what happens when the air cools? • COLD AIR SINKS - more dense air is less buoyant and sinks

  10.    Recap    Loncapa conversion problem!

  11. Warm/Cold Fronts: MovingCold meets Warm WARM COLD • Cold air mass pushes against warm air mass. • Warm air rises, cools off and forms clouds (Cumulus type). Question: Why are they called weather fronts? Illustration taken from “Weather” by Readers’ Digest

  12. Warm/Cold Fronts: MovingWarm meets Cold WARM COLD • Warm air pushes towards cold air, sliding on top of it. • Rising air cools off and forms clouds (Stratus type). Question: Why do clouds form when (moist) warm air rises?>> We'll be talking about this soon! Illustration taken from “Weather” by Readers’ Digest

  13. Water Cycle Condensation Precipitation Evaporation Collection Illustration taken from www.kidzone.ws/water/

  14. Water Cycle Match the word to its description. (1) condensation (2) precipitation (3) evaporation > Which step in the water cycle does not require or release energy and involves no phase change? > Which step in the water cycle releases energy and causes water to change from the gas to the liquid phase? > Which step in the water cycle requires energy and causes water to change from the liquid to the gas phase?

  15. ACTIVITY: Make Clouds with Dry Ice Put dry ice (frozen CO2) into water and watch it bubble and form a cloud. Put your hand over the water. Does the cloud make your hand feel warm or cold? Does the cloud make your hand feel wet or dry? Why is the dry ice bubbling? (Hint: sublimation) Why is a cloud forming and what is it made of?

  16. ACTIVITY: Making Clouds (wrap-up) • What was the point of this activity? • Explain how you would introduce this to your class. • Where do you see a student having difficulty with this? • What changes or extensions could you do to this activity?

  17. Dry Ice and Clouds Dry ice (or solid CO2) is added to water. Vigorous bubbling occurs in the water and a cloud forms above the water surface. Select all of the true statements below. (1) The cloud is made of water vapor (or gas). (2) The bubbles in the water contain mostly carbon dioxide. (3) The cloud and the water feel hot. (4) The cloud is made of water that comes from hot steam rising from the boiling water. (5) The cloud is made of carbon dioxide. (6) The cloud is made of condensed liquid water droplets.

  18.    Recap    Explain this picture Micro wave FM AM Radio Waves Infrared UV X-rays Gamma Rays Visible Light Violet Red

  19. Cloud Formation: Different Mechanisms Warm humid airrises, cools off, and water vapor condenses into water droplets. Warm humid air encounters a mountain and rises. Warm humid air in a warm front encounters a cold front and rises. Illustration taken from “Weather” by Readers’ Digest

  20. Cloud Types: “Low” Stratocumulus Cumulus “heap” Cumulonimbus Stratus“spread out” Illustration taken from “Weather” by Readers’ Digest

  21. Cloud Types: “Middle” Altocumulus Cumulonimbus Altostratus (high) Illustration taken from “Weather” by Readers’ Digest

  22. Cloud Types: “High” Cirrus “curl” Cumulonimbus Cirrocumulus Cirrostratus Illustration taken from “Weather” by Readers’ Digest

  23. Table Time Questions • Glider pilots need “thermals” (rising hot air) to lift their planes!They usually fly later in the day. Why? • Glider pilots find thermals by going beneath cloud formations. Why? • Why do cumulus clouds have flat bottoms?

  24. Cloud Formation: Mountain Range Effect Windward Leeward • Windward side of mountain where warm air rises receives precipitation, but leeward side receives little moisture. • Example = Denver, CO! Moisture from Pacific ocean dumps more snow on west vs. east side of Rockies.(Better ski resorts on western slope!) Illustration taken from “Weather” by Readers’ Digest

  25. Types of Heat Transfer Conduction Convection Radiation Water on Stove • Conduction: Vibrations of atoms/molecules transfer heat between objects that touch. (Atoms/molecules do NOT move between objects). • Convection: Atoms/molecules move from hotter to colder regions. • Radiation: All objects radiate electromagnetic waves (infrared radiation), where hotter objects radiate more energy. The sun heats the Earth by radiation. Illustration taken from “The Weather Book” by Jack Williams

  26. Heat Transfer Match the type of heat transfer to the given examples. (1) conduction (2) convection (3) radiation > When the Earth's atmosphere is warmed by the sun. > When hot air meets cold air at a weather front and heat is transferred between the air masses. > When your finger becomes hot due to touching a pot on the stove. > When moist hot air rises and cools off at higher altitudes to form a cloud. > When your skin is warmed while standing in direct sunshine.

  27.    Recap    Explain this picture AIR GLASS Denser Material

  28. Absolute Humidity: Saturation Water Vapor 37 g Grams of Water Vapor per Kilogram of Dry Air 28 g 20 g 15 g 11 g 8 g 6 g 4 g 35°C 30°C 25°C 20°C 15°C 10°C 5°C 0°C Illustrations taken from “The Weather Book” by Jack Williams

  29. Relative Humidity 10 g 30 °C 28 g 10 g 36 % 25 °C 20 g 10 g 50 % 20 °C 15 g 10 g 67 % 15 °C 11 g 10 g 91 % Illustrations taken from “The Weather Book” by Jack Williams

  30. Humidity and Temperature What is the relative humidity of 25 °C (or 77 °F) air that has 18 g of water vapor per 1 kg of dry air? What is the relative humidity of 5 °C (or 41 °F) air that has 3 g of water vapor per 1 kg of dry air?

  31. Weather-related Instruments Match the weather-related instrument to its description. (a) thermometer (b) barometer (c) anemometer (d) hygrometer > Instrument to measure temperature. > Instrument to measure wind speed. > Instrument to measure humidity/moisture. > Instrument to measure air pressure.

  32. Hurricanes: The Greatest Storms on Earth Hurricane Wilma movie (2005) Question: What features of the hurricane did you see? http://www.nasa.gov/mpg/149564main_wilma_sst.mpg http://www.nasa.gov/vision/earth/lookingatearth/hurricane_multimedia.html

  33. What does a Hurricane Need to Start? red = 85 to 95 °F Hurricane Katrina (2005) • WARM ocean water temperatures (> 80 ° F)! (stores ENERGY!!) • LOW PRESSURE core (creates circulation of moist air). http://www.physicscentral.org/explore/action/hurricane-1.cfm http://www.nasa.gov/vision/earth/lookingatearth/hurricane_multimedia.html

  34. Anatomy of a Hurricane Hurricane Floyd movie (1999) http://www.suu.edu/faculty/colberg/Hazards/Hurricanes_Noreasters/Hurricane_Anim_2.html

  35. Hurricanes: Air Movement http://earthobservatory.nasa.gov/Library/Hurricanes/

  36. Energy in Evaporation and Condensation Evaporation = Humid Air Condensation = Liquid droplets Question: Is the energy required to evaporate 1 kg of liquid water(a)less than OR (b)equal to OR (c)greater thanthe energy released when 1 kg of vapor condenses into liquid?

  37. POWER of a Hurricane Energy released via RAIN (condensation) In one day, assume about ½” rain falls over a 400-mile radius (~20 trillion kg H2O). Multiply by the heat released during condensation (600 kcal/kg or 2500 kJ/kg) Equals power of about 600 TW !!! Question: How many times greater is this hurricane power than worldwide power consumption (= 15 TW)? 600 TW !!! Grey (1981) via Chris Landsea (NOAA) - PBS NOVAscienceNOW site

  38.    Recap    Explain these pictures

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