Unit 5

Mean total column water vapor distribution for 1988-1992
Mean total column water vapor distribution for 1988-1992

Moist air is important for weather, climate, air quality despite its low, strongly varying fraction of 0 to 4%. Besides its role in the water cycle, water vapor is also playing a large role in the energy-, and trace gas cycle. Water vapor is involved in cloud and precipitation formation, affects radiation, and many gas-phase chemical and aerosol processes.

Water is the only atmospheric constituent that occurs in all its phases in the troposphere. For simplicity we will deal with the moist atmosphere first before, in a later unit, we address phase transition processes between gaseous, liquid & solid states of water. The moisture measures we define in this unit only apply to water vapor.

Mean water vapor distribution in the Northern and Southern hemisphere in the annual cycle
Mean water vapor distribution in the Northern and Southern hemisphere in the annual cycle for various years

Learning goal

Describing the moist atmosphere.

Students’ Tasks

  1. Watch the videos on the material that will be discussed in class
  2. Read chapter 2.7 to 2.7.6 (included) of Lectures in Meteorology
  3. Be prepared to present the material learned
  4. Fill out the equation sheet prior to class
  5. Answer the questionnaire by 1500 AST the day before the class.

In case you want to take notes on the slides used in the video, here they are.

Worked example problem

Show that water vapor pressure decreases when the air parcel expands under isotherm conditions.

Class preview

We will solve the problems listed in this task sheet, among other things.