Unit 1

Atmospheric composition and vertical  structure of the atmosphere – spatial and temporal aspects

This unit introduces you to the medium that this course is about: The atmosphere of the Earth.

#Lectures in Meteorology
Temporal evolution of the CO2 concentration as measured at Mauna Loa, HI

Learning goals

After completion of this unit, students will be able to

  1. Explain the vertical structure of the atmosphere under the aspects of temperature, composition, pressure, ionization, escape velocity, and magnetism
  2. Identify the processes that lead to the observed vertical structure of Earth’s atmosphere
  3. Recall horizontal and vertical distributions of atmospheric constituents
  4. Name sources and sinks of constituents

Students’ tasks

  1. Watch this video that summarizes the material
  2. Read chapter 1.1 and 1.3 to 1.4 (included) of Lectures in Meteorology that discus the atmospheric composition and vertical structure.
  3. Fill out this questionnaire by 1500 AST of the day before class. Use the book for help. The first part of the questionnaire serves for taking notes. It also prepares the student to present the material in class. This part is pass/fail and part of the homework grade. The second part of the questionnaire measures knowledge and comprehension. It will be graded according to the percentage of correct completions over the semester as part of the homework grade. Note that I read these parts to analyze where the class had difficulties to address them. The last question of the questionnaire serves to seek clarification from me. When you have no questions, type “N/A”. Failure of submission of the questionnaire in time leads to an F. Note that these grading policies apply to all questionnaires in this class.
  4. Prepare to present the material using your notes. When you are chosen to be the presenter, I will grade the presentation for completeness, and correctness. When you are a graduate student, your presentation as such will be also graded.
  5. Take this quiz. You are allowed to take your notes, re-watch the movie, and/or re-read sections in the book for help when taking the quiz. Please check the material again, when you are in doubt. The purpose of the quiz is to ensure that you recall the vertical structure, the horizontal distribution, sources and sinks of constituents. The above learning objectives are critical for discussion of atmospheric thermodynamics, dynamics, and chemistry. Revisit the facts to remember them. In the quiz, you also will combine them and put them into a new context. The quiz will be graded by percentage of correct completion. Note that these rules apply to all future online quizzes.

Test your knowledge and comprehension (optional)

Question 1
Question 2

Additional material for the interested student

More information on the aurora.

FAQ

Q: Is water vapor the only major constituent difference between troposphere and stratosphere?

A: No. The concentrations of ozone, for instance, are much higher in the stratosphere than in the troposphere.

Q: Is there a notable difference in stratospheric ozone concentrations between the North Pole and South Pole? If yes, would it mainly due to dynamical processes or chemical processes?

A: In the respective hemispheric spring, stratospheric ozone concentrations go down. Once the Sun comes back in spring, photolysis and photo-chemistry start. Typically, spring ozone concentrations are lower at the South Pole as the cold high plateau and the quasi-circular circulation in the Antarctic cut off the exchange with the mid-latitudes. The high albedo of snow may increase photolysis rates near the surface. Thus, the high plateau on the South Pole means that this process sets on comparatively earlier than at the North Pole.

Q: The equation for probable escape velocity – it has two mass terms, M, and m. Is this a typo?

A: Yes. The probable escape velocity depends on the mass of the molecule.

Q: What is the difference between main gases of the dry atmosphere, trace gases and greenhouse gases?

A: The main gases of the dry atmosphere are N2, O2, Ar, and CO2. Trace gases are all gases that contribute with far less than ppt to the total composition, but may locally have much higher concentrations. Greenhouse gases absorb solar radiation, for instance, CO2, H2O vapor, or CH4. They can be a trace gas, e.g. CH4, but must not be a trace gas, e.g. CO2.

Class work sheet

In class, students will work, among other things, on these problems.

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