1 / 30

Chapter 27 - Clouds

Chapter 27 - Clouds. Use of Power Point design and animations with permission from Dr. Joby Hilliker ( West Chester University, West Chester, PA. CHAPTER 6 - CLOUDS. How is a cloud formed?

leontyne-durand
Télécharger la présentation

Chapter 27 - Clouds

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 27 - Clouds Use of Power Point design and animations with permission from Dr. Joby Hilliker ( West Chester University, West Chester, PA

  2. CHAPTER 6 - CLOUDS • How is a cloud formed? • An air parcel containing water vapor (gas) is cooled to the dewpoint such that the water vapor condensesto form water droplets (liquid). = Liquid water droplets • When condensation occurs, the air parcel is ”saturated”(RH=100%)

  3. Unsaturated Parcels Generic Cloud Saturated Parcels

  4. CHAPTER 6 - CLOUDS • When condensation occurs, the air parcel is ”saturated”(RH=100%) • The temp. at which saturation (and condensation) will occur is the dewpoint • The farther the dewpoint is below the air temp, the lower the RH, and the less likely clouds will form.

  5. 6 6 6 6 Density of Surrounding Air 6 z CHAPTER 6 - RISING PARCELS • How can an air parcel cool to the dewpoint? • Get it to rise! • How can this happen? • Density of parcel needs to be less than surrounding air 3 Density of Main Air Parcel

  6. 60 60 60 60 Temp. of Surrounding Air 60 z CHAPTER 6 - RISING PARCELS • Translate density into temperature: • Warmer air is less dense; Colder air is more dense • A parcel will rise if it’s warmer than surrounding air. • “Warm air rises” concept 70 Temp. of Main Air Parcel

  7. CHAPTER 6 - RISING PARCELS What happens when a parcel rises? • It expands • Finds itself in an environment with lesser density/pressure • It coolsadiabatically • Takes work (thermal energy) to expand parcel • adiabatic= no heat exchange between parcel and environment • parcels cools at the dry adiabatic lapse rate (DALR), which is 5.5°F / 1000 feet 60 F z 70 F

  8. CHAPTER 6 - RISING PARCELS To determine if a parcel will rise, compare: a. the parcel’s temperature which cools at a constant rate …at a given altitude to… b. temp. of surrounding parcels changes on a daily basis; is measured (i.e., the atmosphere) RULE #1: • As long as the rising parcel is warmerthan surrounding air parcels at a given altitude, the parcel will continue to rise • If parcel becomes colder, it will sink

  9. Parcels going all the way up to 50,000 feet!

  10. CHAPTER 6 - CASE #1 • Steep lapse rate (_________ ATMOSPHERE): Parcel rises to tropopause Result: Thunderstorms! UNSTABLE Parcel cools ...and if drops to dewpoint Lapse Rate (steep) Saturation z COLD Temperature HOT

  11. Cumulo-nimbus (Thunderstorm)

  12. Cumulonimbus

  13. Cumulonimbus

  14. CHAPTER 6 - CASE #2 • Steep lapse rate near ground, weak aloft: Parcel rises to a point, then stops Result: Cumulus (weak) Parcel cools Lapse Rate ...and if drops to dewpoint (steep) Saturation z COLD Temperature HOT

  15. "Cumulus" 3000 - 8000 feet

  16. Cumulus 3000 - 8000 feet

  17. Alto-cumulus 10000 - 20000 feet

  18. Alto-cumulus 10000 - 20000 feet

  19. Cirro-cumulus 20000-40000 feet

  20. CHAPTER 6 - CASE #3 • Weak lapse rate (_________ ATMOSPHERE): Parcel rises only slightly Result: Stratus STABLE Lapse Rate (weak) z COLD Temperature HOT

  21. "Stratus" 0 - 8000 feet

  22. Stratus 0 - 8000 feet

  23. Altostratus 10000 - 20000 feet

  24. Altostratus 10000 - 20000 feet

  25. Cirrostratus 20000 - 40000 feet

  26. CHAPTER 6 - SUMMARY OF CLOUDS • Cloud type reveals: …how quickly temperature is decreasing w/ height • CUMULUSSTRATUS Unstable AtmosphereStable Atmosphere High Lapse Rate Low Lapse Rate Deep, Vertical DevelopmentThin, Spread out

  27. CHAPTER 6 - SUMMARY OF CLOUDS • If parcel can rise: • Cloud Top = where parcel is no longer warmer than surrounding air • Cloud Base = where saturation occurs • What could I infer about atmosphere if it is CLEAR? • Sinking air • Lack of moisture (low dewpoint)

  28. Cirrus 30000 feet + Composed of Ice Crystals

  29. Contrails 30000 feet + Composed of Ice Crystals

  30. CLOUD NOMENCLATURE

More Related