If you've read the module on clouds and moisture, you already know the basics of how precipitation is formed. Essentially, upward motion cools the air. Once the air is cold enough, it becomes saturated with water vapor. Any further upward motion causes some of the vapor to liquefy, producing clouds and precipitation.

There are a few details left out of the above description. The real world is much more interesting and much more complex than the simple one-paragraph description of precipitation formation. Among the interesting complications are the details of what makes the air ascend, how the temperature of the air changes during ascent and condensation, how the water vapor manages to condense into cloud droplets and ice crystals, and how you make rain and snow from a cloud. This module deals with the first two issues: the interplay between the vertical temperature structure of the atmosphere and the temperature of the ascending air.


  1. To understand the dry and moist adiabatic lapse rates.
  2. To be able to read and interpret a sounding diagram.
  3. To be able to determine the change in temperature as air parcels rise or sink.


  1. Air Parcel Ascent
  2. Introduction to Sounding Diagrams
  3. Moist Ascent
  4. Ascent of a Typical Air Parcel
  5. The Complete Sounding Diagram
  6. Dew Point and Mixing Ratio
  7. Cloud Base
  8. Chinook Wind
  9. Summary

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Questions or Comments

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