General circulation of the atmosphere

Semester 1 2026



General Information

The honours/master's level unit "General circulation of the atmosphere" will be running during semester 1, 2026. The unit will be taught by Martin Singh.

There are two 1.5-hour classes per week at the following times:

  • Monday 10am-11:30am: Rm 115 in 9 Rainforest Walk
  • Thursday 1pm-2:30pm: Rm 115 in 9 Rainforest Walk

There will also be a 1-hour drop-in session for help with assignements every week on Monday at 1pm in my office (Rm 2.21 in 9 Rainforest Walk).

Classes will run for weeks 1-12 of semester 1, between the 2nd of March and the 29th of May. However, there will be no classes in the week of the 18th of May (week 11) and the week of the 6th of April (the mid-semester break).

Exam

The exam will be take home, to be done in the weke of the 8th of June. Exact format and dates to be confirmed.



Unit details

This unit introduces students to the large-scale circulation in Earth’s atmosphere and the processes by which this circulation is maintained. The unit will begin with a discussion of the mathematical techniques used to estimate the atmospheric state and analyse the behaviour of atmospheric circulations. This will include an introduction to state estimation and data assimilation as well as a discussion of Reynold’s decomposition and its application to the analysis of atmospheric motions.

Next, the unit will introduce the basic theory underpinning the tropical general circulation, including the Hadley circulation and monsoons. Theoretical concepts will be demonstrated using real-world data from the atmosphere and in qualitative experiments using a rotating tank apparatus.

The unit will also consider the midlatitude circulation and the maintenance of the global angular momentum budget. Concepts of eddy-mean flow interaction and the transformed Eulerian mean will be used to explain the formation of jets at midlatitudes, and the existence of the thermally indirect Ferrel cell.

Finally, the course will consider the water budget of the atmosphere and theories of how it may vary in the future. This will serve as an entry point for students to engage with the scientific literature regarding changes in the atmospheric general circulation with climate change.

Unit outcomes

On completion of this unit students will be able to:

  1. Describe the various analysis techniques used to estimate the atmospheric thermodynamic state and large-scale circulation and evaluate their strengths and weaknesses.
  2. Identify the main features of the atmospheric circulation and the processes that contribute to their maintenance.
  3. Apply mathematical tools to analyse the transports of energy, momentum and water through the atmosphere.
  4. Critically engage with the scientific literature regarding the large-scale atmospheric circulation and its possible changes under climate change.

Assessment

Assessment in this unit is a combination of assignments and reports (50%) and an end-of-semester exam (50%).

The breakdown of marks for the unit is as follows:

  1. Assignment 1: 15%
    • Available: 23rd March
    • Due: 17th April
  2. Assignment 2: 15%
    • Available: 20th April
    • Due: 15th May
  3. Paper report and presentation: 20%
    Students are required to summarise a paper from the literature (1500 words) and present it the class orally (10 minutes). .
    • Due 29th May
  4. Exam: 50%
    Open book written exam.
    • Week of the 8th June

Syllabus

The unit will cover the following topics.
  1. Overview & tools
    • An introduction to the general circulation, including a short discussion of historical study of the general circulation and its observed structure. We will also iontroduce the governing equations of the atmosphere that will be used throughout the rest of the unit.
  2. Radiative-convective equilibrium & Hide's theorem
    • In this topic, we ask the question: why does the atmosphere circulate? To answer this, we discuss how the atmosphere would look if their was no large-scale circulation, a state known as radiative-convective equilibrium, and we will show that this state cannot exist because it violates something called Hide's theorem.
  3. Axisymetric circulations
    • Having shown that the atmosphere must circulate, we now calculate how this circulation would look in an axisymmetric atmosphere--one with no variations in longitude. This is the famous Held & Hou model for the Earth's Hadley Cell. The Held & Hou model is an instructive special case, but as we will see, it is far from the real circulation.
  4. The angular-momentum budget
    • We now shift focus to the extratropics and begin to discuss the role played by "eddies"--zonal and time variations--in the general circulation. We do this by considering the atmospheric budget of angular momentum. We will show that by understanding the angular momentum budget, we can understand much about the atmosphere's large-scale structure.
  5. Jet dynamics
    • In this topic, we elucidate how and why the atmosphere produces jets. We will begin by considering a simple "barotropic" view, which does not include temperature gradients or vertical variations, but this will prove instructive for the core physics of jet formation in planetary atmospheres.
  6. Quasigeostrophy
    • To understand the dynamics at a deeper level, we need to introduce the theory of quasigeostrophy. We will show how QG concepts such as Eliassen-Palm fluxes allow us to understand the mid-latitude general circulation, including feedbacks between the eddies and the mean flow.
  7. Eddies and the tropical circulation
    • Finally, we return once more to the tropics and discuss how eddies influence the tropical circulation. We consider these eddy effects on the Hadley Cell, and how they influence its seasonal variations that manifest as regional monsoons.