Atmosphere, Ocean and Climate Dynamics

Transcription

1 Atmosphere, Ocean and Climate Dynamics Instructor Raffaele Ferrari, Teaching Assistants TAs: Allison Wing and Rebecca Dell Webpage

2 Atmosphere, Ocean and Climate Dynamics Meeting times Monday, Wednesday and Friday Classroom Prerequisites Multivariable Calculus (18.02) Physics I: Classical Mechanics (8.01)

3 Atmosphere, Ocean and Climate Dynamics Course description: This undergraduate class is designed to introduce students to the physics that govern the circulation of the ocean and atmosphere. The focus of the course is on the processes that control the climate of the planet. Grading: The assessment will be in three parts (with weight toward final grade): 1. Homework assignments will be handed out each week. These will serve a multiple purpose: As a component of the teaching process, as an assessment of performance, and as a means of providing feedback to me. (35%; the two lowest marks will be given half-weight) 2. Class participation. (5%) 3. A mid-term test. (20%) 4. A final, closed book, exam on all assessable course material. (40%) Commitment: 3 hours of lectures 1 hour of recitation 10 hours per week 6 hours of homework (on average)

4 Atmosphere, Ocean and Climate Dynamics Textbook Marshall, John, and R. Alan Plumb. Atmosphere, Ocean, and Climate Dynamics: An Introductory Text. Boston, MA: Elsevier Academic Press, Other Useful Reading Material Hartmann. Global Physical Climatology. International Geophysics Series. Vol. 56. San Diego, CA: Academic Press, This book should prove useful for both atmospheric and oceanic sections of the course, especially chapters 1-7 of the book, which cover the first two months of class material. Houghton. The Physics of Atmospheres. Cambridge, UK: Cambridge University Press, For the atmosphere, detailed treatment of radiation, and simple and intelligible treatment of dynamics. Wallace and Hobbs. Atmospheric Science: An Introductory Survey. New York, NY: Academic Press, Good qualitative discussion of many of the topics we will cover in atmospheric science. Stewart. Introduction to Physical Oceanography. Available for free as a PDF file. A not-too-technical introduction to physical oceanography.

5 Atmosphere, Ocean and Climate Dynamics Course syllabus (1) The global energy balance of the Earth (2) The equations of fluid motion (3) The general circulation of the atmosphere (4) The general circulation of the ocean (5) Climate and climate variability Laboratory experiments Rotating flow experiments GFD Lab (Green Building ) and portable rotating tank

6 Atmosphere, Ocean and Climate Dynamics Course syllabus (1) The global energy balance of the Earth (2) The equations of fluid motion (3) The general circulation of the atmosphere (4) The general circulation of the ocean (5) Climate and climate variability Laboratory experiments Rotating flow experiments

7 Atmosphere, Ocean and Climate Dynamics Lecture II Characteristics of the Atmosphere

8 Lecture II Outline 1. Geometry of the Earth 2. Chemical composition of the atmosphere

9 Components of the Climate System 1. Atmosphere fast timescales (days to weeks) 2. Hydrosphere intermediate timescales (decades to millenia) 3. Cryosphere slow timescales (> 100 years) 4. Lithosphere very slow timescales (> 10,000 years) 5. Biosphere all timescales

10 Geometry of litosphere Earth is a rotating oblate spheroid 70% of the litosphere is covered by ocean 70% of emerged land is in Northern Hemisphere Ω = v r = 2πR/day R = 2π day = s

11 Geometry of litosphere Emerged land rarely exceeds 2 km atmosphere flows above slightly corrugated surface Oceans are on average 4 km deep oceans sit in deeply corrugated basins

12 Characteristics of the amosphere ρ(z) = ρ 0 e z/h ρ 0 = 1.35 kg/m 3 H = 6.8 km

13 Characteristics of the amosphere 10 km 6370 km

14 Characteristics of the amosphere Gravity is approx. constant throughout atmosphere g 9.81 m/s 2 10 km 6370 km

15 Chemical composition of atmosphere The chemical composition of Earth s atmosphere differs from that of other planets in the solar system

16 Abundance of chemical elements in the solar system

17 Atmospheric loss Atmospheres can lose atoms, especially low mass ones, if they can exceed escape velocity (Jeans escape) Escape velocity V e = 2GM/R Mean molecular velocity at top of the atmosphere (exosphere, km, T =1000 K) V m = 3kT/m Boltzmann distribution implies that negligible number of molecules have V > 3Vm Molecular hydrogen has 3Vm = 12 km/s Jupiter has Ve = 60 km/s, Earth has Ve = 11 km/s H 2 cannot escape from gas giants like Jupiter, but is easily lost from lower-mass bodies like Earth or Mars

18 Chemical composition of atmosphere Life changed the chemical composition of Earth s atmosphere Photosynthesis Nitrogen Cycle

19 Earth s atmospheric composition Atmospheric composition is constant below 50 km Water vapor and CO 2 are strongest absorbers in infrared Atmospheric Composition Gas Name Nitrogen Oxygen *Water Argon *Carbon Dioxide Neon Helium *Methane Hydrogen *Nitrous Oxide *Ozone Chemical Formula N2 O2 H2O Ar CO2 Ne He CH4 H2 N2O O3 * variable gases Percent Volume 78.08% 20.95% 0 to 4% 0.93% % % % % % % %

20 CO 2 concentration and climate