1 / 18

Class #25: Friday, March 6

Class #25: Friday, March 6. Clouds, fronts, precipitation processes, upper-level waves, and the extratropical cyclone. Ice crystal formation. The ice crystal process begins with the formation of ice crystals At temperatures below -40ºC, ice crystals can form spontaneously (deposition)

aqua
Download Presentation

Class #25: Friday, March 6

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. Class #25: Friday, March 6 Clouds, fronts, precipitation processes, upper-level waves, and the extratropical cyclone Class #25: Friday, March 6, 2009

  2. Ice crystal formation • The ice crystal process begins with the formation of ice crystals • At temperatures below -40ºC, ice crystals can form spontaneously (deposition) • At higher temperatures, small particles called ice nuclei form surfaces for water vapor to freeze. • There are lots less ice nuclei than CCN Class #25: Friday, March 6, 2009

  3. Mixed clouds have water droplets and ice crystals • At temperatures just below freezing, few substances can act as ice nuclei • At lower temperatures (higher in the cloud) more substances can act as ice nuclei • Ice nuclei have molecular structures similar to the ice crystal • Condensation of supercooled water occurs for T<0º without an ice nucleus Class #25: Friday, March 6, 2009

  4. Ice crystals can also act as ice nuclei Class #25: Friday, March 6, 2009

  5. Ice crystal types depend on temperature Class #25: Friday, March 6, 2009

  6. The ice crystal process in a cloud of mixed ice and liquid • The ice crystal process takes place when a few ice crystals are present with supercooled liquid cloud droplets • The saturation vapor pressure is lower for ice than for water • Water vapor diffuses to deposit on the supersaturated crystals and evaporate from the subsaturated drops. Class #25: Friday, March 6, 2009

  7. Saturation vapor pressure favors growth of ice crystals Class #25: Friday, March 6, 2009

  8. Saturation vapor pressure over ice < liquid water Class #25: Friday, March 6, 2009

  9. A few ice crystals grow at the expense of many droplets Class #25: Friday, March 6, 2009

  10. Aggregation: the process of collision and collection of ice Class #25: Friday, March 6, 2009

  11. Overview of the precipitation-formation process Class #25: Friday, March 6, 2009

  12. Different precipitation types: they depend on the sounding Class #25: Friday, March 6, 2009

  13. Even in summer clouds have snow and ice Class #25: Friday, March 6, 2009

  14. Snowfall with subfreezing temperatures below cloud base Class #25: Friday, March 6, 2009

  15. A shallow sub-freezing layer at the ground and freezing rain Class #25: Friday, March 6, 2009

  16. Sleet (ice pellets) with a deeper surface-based inversion Class #25: Friday, March 6, 2009

  17. Hours of freezing rain per year on average varies greatly Class #25: Friday, March 6, 2009

  18. Mean snowfall amounts over the continental U.S. Class #25: Friday, March 6, 2009

More Related