1 / 31

Lecture 10 Precipitation Processes & Types

Lecture 10 Precipitation Processes & Types. How Precipitation Forms. It’s actually really hard to make a rain drop Cloud drops are VERY TINY Rain drops are VERY BIG. Cloud droplet (D p = 10um, V = 5.2x10 2 um 3 ). Cloud Drop. It takes 1 MILLION cloud droplets to make 1 rain drop!!.

kendall
Download Presentation

Lecture 10 Precipitation Processes & Types

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. Lecture 10Precipitation Processes&Types

  2. How Precipitation Forms • It’s actually really hard to make a rain drop • Cloud drops are VERY TINY • Rain drops are VERY BIG

  3. Cloud droplet (Dp= 10um, V = 5.2x102 um3) Cloud Drop It takes 1 MILLION cloud droplets to make 1 rain drop!!

  4. Precipitation in Cold Clouds • Ice, water and water vapor exist at the same time. • Cloud drops DON’T FREEZE at 0C!! • Liquid water won’t freeze until -40C • SUPERCOOLED • Supercooled water freezes when it touches aFreezing Nuclei • FN are rare

  5. Bergeron Process

  6. The Bergeron Process One little ice crystal and lots of water droplets Grows Bigger by “Stealing” moisture from the Cloud droplets

  7. Precipitation in Cold Clouds • Saturation vapor pressure above ice crystals is somewhat lower than above supercooled liquid droplets • It’s easier for water vapor to escape from the supercooled liquid

  8. Precipitation in Warm Clouds • In warm clouds there are no Ice Crystals so the Bergeron Process can’t operate • Collision-Coalescencea.k.a. Bump and Stick • Need one BIGGER than average Cloud Drop

  9. Collision-Coalescence Large Cloud Drop (55 um) Small Drop (100 um) Cloud Drop (10 um) Rain Drop (1000 um) BIG drops fall FASTER than SMALL drops!!!!

  10. Cloud Seeding and Precipitation • Termed WX-Mod • Weather Modification • “Fake Ice” to simulate the Bergeron Process • Dry Ice • Silver Iodide

  11. Cloud Seeding and Precipitation • Hard to “prove” that it actually worked. • Need the right ratio of cloud droplets to ice crystals. • Concern over toxicity of silver iodide. • You can “overseed” a cloud and too many ice crystals are formed so it doesn’t rain • You can also “overseed” cold fog with dry ice to dissipate it.

  12. Forms of Precipitation • Rain • Snow • Sleet and Glaze • Hail • Rime

  13. Raindrop?

  14. Rain • Drops of water that fall from a cloud and have a diameter of at least 0.5 millimeter. • Most rain starts as SNOW and MELTS • Small drops are called DRIZZLE and MIST • Virga – Rain that evaporates before reaching the surface.

  15. Atmospheric Profile for Rain

  16. Heavy Rain in Action

  17. Snow • Ice crystals and clumps of Ice crystals • Very Cold Conditions: Individual crystals make “light snow” • ‘Warmer’ Cold Conditions: Crystalsform clumps “wet snow”

  18. Atmospheric Profile for Snow

  19. Time Lapse of Blizzard

  20. Sleet • Rain that freezes near the surface • Wintertime phenomenon • Clear to translucent pellets (Ice Pellets) Snow Melts Refreezes

  21. Atmospheric Profile for Sleet

  22. Freezing Rain and Glaze • Rain or drizzle that falls in liquid form and then freezes uponstriking a cold object or ground. • The coating of ice is called Glaze.

  23. Profile for Freezing Rain

  24. Interactive Images for Precip • http://apollo.lsc.vsc.edu/classes/met130/notes/chapter7/51_Sleet/A_51.swf • Click on the link above

  25. Hail • Rounded WHITISH Pellets and Irregular lumps of ice • Usually 1-5 cm • Can weigh up to a pound. • Can be very destructive • Cars • Crops • Can KILL People

  26. Hail Formation in Words • Produced in a Cumulonimbuscloud • Grauple or large frozen rain drops act as embryos • ACCRETION: They accumulate supercooled water, adding new layer • Violent, upsurging air currents within the storm carry these embryos up through the cloud. • Low liquid water makes a white layer • Higher liquid water makes a clear layer • When the updraft can no longer keep it aloft it falls to the surface.

  27. Hail Formation Diagram

  28. Hail Formation Video • http://www.atmosedu.com/meteor/Animations/52_Hail/52.html

  29. Baseball Sized Hail in Action https://www.youtube.com/watch?v=OFv2W7Duqiw

  30. Rime • This is a deposit of ice crystals • Formed by freezing of supercooled fog or cloud droplets on objects whose surface is below freezing

  31. Rime in Action https://www.youtube.com/watch?v=6CDgxrjaLOI https://www.youtube.com/watch?v=30BwkE0BYWA

More Related