Planetary Climate -- A new PtyS graduate course

Syllabus for Planetary Climate

Units: 3

Offered: Spring 2011

Instructor: Adam Showman, Space Sciences 430, 621-4021

Course description (for catalog): Physical and chemical processes governing the climate of planets. Climate feedbacks and stability; greenhouse effect, ice-albedo feedback, cloud feedbacks. Effect of atmospheric circulation on climate. Milankovitch cycles and ice ages. Long-term atmospheric evolution; runaway greenhouse, Snowball Earth, atmospheric loss/collapse, faint young Sun problem. Interaction of climate with geology/biology. Observable signatures. Habitable zones. Application to Earth, Mars, Venus, Titan, and habitability of extrasolar planets.

Course objectives: This is a graduate-level course that will provide an overview of the physics and dynamics of the climate of planets. The target audience is graduate students in ATMO and PtyS. Students from astronomy and HWR may also be interested. In addition to students primarily focusing on atmospheric studies, I hope to attract students whose research involves (for example) Mars/Titan geomorphology or exoplanets. My intention is to provide a course that complements Ptys 517 ("Atmospheres and Remote Sensing") as well as existing courses in the ATMO department.

Text: Pierrehumbert's upcoming book Principles of Planetary Climate, which will be published in June 2010, will make a good textbook. I will also hand out detailed lecture notes and assign reading of important papers from the peer-reviewed literature.

Topics Covered:

Basics of radiative transfer as needed for studying climate: greenhouse effect etc.

Feedbacks: thermal feedback, ice-albedo feedback, "condensable gas" feedbacks (water vapor on Earth, carbon dioxide on early Mars/Venus), runaway greenhouse, cloud feedbacks, interaction with geology/biology. Simple (globally-averaged) models of these feedbacks. Multiple equilibria (e.g., a warm Earth versus "Snowball Earth" states). What controls the global-mean temperature of a planet, and its sensitivity to perturbations over a range of timescales.

Introduction to global atmospheric circulation: What are the basic processes that shape the circulation, determine the equator-to-pole (or for sychronously rotating exoplanets, day-night) temperature contrasts, etc. Theoretically possible regimes for an atmospheric circulation; overview of circulation regimes of actual planets.

Effect of dynamics on climate feedbacks; interaction of the circulation with climate (e.g., effect of latitudinal heat transport on susceptibility of an atmosphere to ice-albedo feedback or atmospheric collapse). Role of a hydrological (or for Titan, methanological) cycle and clouds in climate.

Longer-term climate dynamics: Mechanisms for multi-annual to multi-kyr climate dynamics. Milankovitch cycles (Earth, Mars) and the processes that determine the ice ages (Earth) and distribution of observed glaciers (Mars).

Climate evolution over planetary timescales: Faint-young Sun problem; carbonate/silicate cycles; divergent evolution of Earth, Mars, Venus; discussion of Snowball Earth; mechanisms for atmospheric loss and the resulting climate evolution (e.g., loss of water from Venus, loss of carbon dioxide from Mars, etc); atmospheric evolution, lakes/seas, and the origin of methane on Titan.

Application of climate theory beyond the Solar System: What determines the width of the "habitable zones" around main-sequence stars. Degree to which habitable zone might depend on atmospheric mass, composition, planetary rotation rate, gravity, or other factors. Implications for our search for habitable worlds in the Cosmos.

Observational signatures: While this class is mostly about fundamentals, it is important to relate theoretical knowledge to observations. We will therefore briefly survey the relevant observational records for Earth, Mars, Venus, and Titan, including geology, surface morphology, geochemistry/isotopic signatures, and atmospheric observations, to understand how climate can be inferred. We will also discuss the challenging issue of how observations may illuminate the climate and habitability of exoplanets, including the topic of atmospheric biomarkers that might signal the presence of life on remote worlds.

Prerequisite: The course is intended for introductory planetary science, astronomy, and atmospheric science graduate students. Basic vector calculus and differential equations will be used, and basic familiarity with physics will be needed (some of this will be developed as we go along). There are no specific course prerequisites.

Format: Course will be split between traditional lecture format and a less formal seminar style, led in many cases by students, where we discuss key journal articles or topics.

Grades: The grades will be on an A, B, C, D, E scale and will be based on two components:

40% Homework and 60% Term Project

Given the grades for the homeworks and term paper, the assignment of the final grade will be based on a curve.

The term project is an important aspect of this course -- my aim is to get your creative juices flowing and get you excited about being at the cutting edge of this field. The term project will require a short written paper as well as a presentation at the end of the semester (perhaps during the final exam slot).

There are no exams in this course. However, we may use the final exam slot for presentations, so please reserve it in your schedules for this course.

Course policies:

Feedback: Please let me know how you think the course is going. Suggestions for improvements and ideas for things to try (e.g., topics or activities you'd like to see) are both welcome.

Auditors: I would like to encourage those students auditing this class to choose and carry out a term project. This is a good way of cementing the course material and could lead to research projects that we can continue after the class is over.

Late work: If an assignment is due, you are responsible for turning it in, even if you are absent. All assignments are due at the beginning of class on the due date. Any assignments turned in after that time will be considered late. I will try to be understanding, but I reserve the right to enforce the following policy: Late assignments turned in within one week of the due date will receive one-half credit, after which they will receive zero credit. Please talk to me if you think you can't finish an assignment on time.

Special needs: Students with disabilities who require reasonable accommodations to fully participate in course activities or meet course requirements must register with the Disability Resource Center. If you qualify for services through DRC, bring your letter of accommodations to me as soon as possible.

Academic Integrity: It is strongly recommended that all students read the University of Arizona's Code of Academic Integrity. All students in this course are expected to abide by this code, which will be strictly enforced. Cheating will not be tolerated in any form. Submission of any written work that partially or fully duplicates material from the web, your fellow students, or any other source constitutes plagiarism. Students are encouraged to work together on the homework sets, but unique written responses must be handed in by each student. Instances of plagiarism will lead to a zero on that assignment, with harsher penalties for repeat offenses or extreme cases. Plagiarism on the term project will lead to a failing grade for the course.

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