ATOC 5060 Atmospheric Dynamics Page for class members

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overview | lectures | assignments | forum |resources

Landsat 7 image of von Karman vorticies. As air flows over and around objects in its path, spiraling eddies, known as Von Karman vortices, may form. The vortices in this image were created when prevailing winds sweeping east across the northern Pacific Ocean encountered Alaska's Aleutian Islands. More images http://landsat.gsfc.nasa.gov/earthasart

Overview

An amount of energy from the Sun is intercepted by the Earth. While, exactly this amount of energy is ultimately radiated back to space, Earth’s, spherical shape and rotation causes local imbalance between incoming and outgoing radiation. This discrepancy gives rise to motions that ensure the radiative balance. Understanding the structure and dynamics of the atmosphere is central to forecasting weather and understanding climate.

This course aims to build on knowledge of the fundamental set of physical principles by applying them to quantitatively describe the behavior of large-scale atmospheric motions. By the end of this course we will have developed quantitative analysis of atmospheric propagation and instability of flow associated with  mountain barriers, shallow water waves, large-scale baroclinic Rossby waves and gravity waves. A detailed examination of the development and energetics of  mid-latitude baroclinic cyclones is perused, and the implications for the global scale circulation regime explored. We apply our understanding of atmospheric dynamics to problems of climatological significance, including  tropical circulation, middle atmospheric flow, and the general circulation of the atmosphere.

Instructor: David Noone<dcn@colorado.edu>

When: Spring 2008; Tuesday 11:00-12:15 pm, Thursday 11:00-1:15 pm

Where: Duane E126

Prerequisites: ATOC 5225,  ATOC 5400 or equivalent (ATOC 5050 and calculus may be OK)

Grading: Homework, projects, class reading assignments, mid-term and final exam (100%)

Office hours: After class on Tuesdays, but not 2-3pm. Please use sign-up sheet.

Syllabus: Download the class outline and syllabus, as well as statement on CU procedures.

Textbook: Holton, J. R., An introduction of Dynamic Meteorology, Elsevier Academic Press, 4th ed., 2004

Other texts: Useful secondary references are Gill (1982), Pedlosky (1987), James (1994), Salmon (1998), Vallis (2006)

Lectures and class material

Class notes, overheads, and additional material can be downloaded here. I will place these items here immediately following class (if not prior to class). You should read the relevant sections of the textbook in advance. The references to the sections will always be given well ahead of time. Homework assignments are based on material about half a lecture ahead.

Future dates for assignments are subject to change.

Download a useful list of equations here.

Weekly exercises

Exercise 0: Coriolis parameter

Exercise 1: Review of basic equations

Exercise 2: Forces and PV in a dish

Exercise 3: Acoustic waves

Homework assignments

Homework 1: Quasi-geostrophic relationships (Due: 4pm Tuesday, 12 February)

Homework 2: Waves (Due: 4pm Thursday, 6 March).
See example IDL script: example.pro (solution.pro)
You can also get this directly from atoc.colorado.edu from the directory /home/atoc/dcn/ATOC5060/NCEP
Copy this to your directory on atoc, start IDL (type "idl"), then run the example (type ".run example").
Also in this directory, you will find the NCEP Reanalysis data files. There are a bunch of them, one for each of v velocity ("vwnd") and air temperature ("air"), at each of 500, 100 and 10 hPa, for each of January ("jan") and July ("jul"). So 12 files in total. You do not need to make copies of this data, as the example script (and the one you will create) can read the data directly from the existing location.

If you prefer to use you own machine, you can download all the HW2 data and the example, and try it out. (If you prefer to use something other than IDL, that's fine, but I probably won't be able to help with any code details)

To get you started have a look over the computer and IDL tutorial. Also WARNING fft(v*t) does not equal fft(v)*fft(T)!

Email David if you need an account on atoc. We will have some brief IDL tutorial session in class - bring along questions.

Homework 3: Boundary layers [Assignment update after class!] (Due: 4pm Friday 21 March)
Download the raw data text file  (the columns are: time, voltage V1, time, voltage V2), of the, or a version of the data in excel format.

You can most easily create the graphs and do the analysis using Excel, however, it can also be done in IDL. Either, or any other, way is fine. (Again, the analysis can be done in about 10 minutes in Excel)

Events were (minutes and seconds):

• probes in first position (r₁=2 cm, r₂ = 3.5 cm)
• 00:00  start recording
• 00:15  spin up (5 revolutions in 32.13 seconds)
• 05:08 spin down (no rotation)
• moved probes to second position (r₁=0.2 cm, r₂ = 1.7 cm)
• 11:37 spin up (5 revolutions in 41.86 seconds)
• 13:22 spin up more (5 revolutions in 20.62 seconds)
• 14:39 spin down to no rotation
• 16:45 end recording.

Also, Scott's calibration data for the probes suggest u₁ = 0.61V₁ -0.61, and u₂ = 0.50V₂-0.47, for the velocity u in units of cm/s. Check that your answer to part 1a is close to this. The calibration only matters to get the units for K right in experiment 2.

Movies of the annulus an baroclinic instability from class:

• Spinup (85mb)
• Stepdown from one rotation rate to another (170mb!)

Research projects

Project 1: Baroclinic instability experiment.(Due 4pm Friday 4 April)
Project assignment includes group assessment sheet.

The GFD lab Duane G316. Groups:

• Cassie et al., (5), Thursday 20 March, 12:30-2:00. Download session data
• Brie et al., (5), Thursday 20 March, 3:00-4:30. Download session data
• Sam et al., (4), Friday 21 March, 11:00-12:30. Download session data
• Van et al., (2), Friday 21 March, 1:00-2:30. Download session data

Probe calibration: Scott's probe calibration data.

From Scott: In order to calibrate the V5 velocity probe, use the Probe 1 velocity calibration I gave you for the
spinup/spindown experiment. I have little or no faith in the proper function of velocity probe.

Probe locations

T1 probe 2 mm from the outer cylinder wall at mid-depth.
T2 probe 2 mm from the inner cylinder wall at mid-depth.
T3 probe 2 mm above the bottom surface at mid-gap
T4 probe 5 mm below the top surface of the fluid at mid-gap.
V5 probe 5 mm below the top surface of the fluid at mid-gap.
 

Thermal expansion coefficient of silicon oil = 0.00105 cc/cc/K
Fluid depth = 47 mm
Probe diameter =1.5 mm
 

Movies of the annulus and instability:

• Hadley Regime (10 mb)
• Transition to wave regime (28 mb)
• Baroclinic growth in a GCM (use quicktime to view "fli" files) (55 mb)
• Atmospheric waves viewed with water vapor (50 mb)

Project 2: The general circulation (Due 4pm FRIDAY 2 May) <-- NOTE CORRECTION!
Assignment sheet including a guide to your report, also Tutorial 1 handout and Tutorial 2 handout.

Everything you need to get the model running on atoc is in the tutorial sheets. To run this on your own system you will need a fortran compiler, and the netcdf library, and IDL. The model has a home page at Planet Simulator. Also, read the User's Guide, and Reference Guide. The latter described the model in detail. You can also read the project README file here

Alternatively, download the model tarball plasim5060_2008.tar.gz, and extract the files with:

zcat plasim5060_2008.tar.gz | tar xvf -

This will create a directory called plasim5060_2008 - which contains the README file, which contains further detailed instructions.
 

Presentations: 7 minutes (5 minutes + 2 for questions)
Email David a powerpoint presentation ahead of class. Powerpoint should be about 3 slides: 1) Intro, description, hypthesis, 2) One (many two) key results/figures, 3) Summary conclusions.

Thursday 24 April: Matthias, Katelynn, Laura, Melissa, Justin, Marcus, Cassie, Xiaoyan

Tuesday 29 April: Krystyna, Rick, David, Yolanda, Sam, Brie, Heather, Eric, Van

Exams

Midterm: late February/early March

Final Exam: Monday, 5 May 2008, 1:30-4:00pm, Duane E126

Study guide

Example equations

Resources

The class textbook is a classic in the field. There are numerous copies of all editions in the library. While "Holton" covers many aspects of atmospheric dynamics, it lacks certain mathematic rigor and detailed treatment of various topics and phenomena.

Below is a non-exhaustive list of additional textbooks that cover aspects of the syllabus. Most of these are available in the Math/Physics library. These provide a somewhat more detailed description than Holton. I have omitted from this list texts which provide more qualitative treatment of dynamics, although such texts are also available in the library and valuable additions to your reading.

Andrews, G. D., Holton, J. R., and Leovy, C. B., Middle Atmosphere Dynamics, Academic Press, 1987.

Gill, E., A., Atmosphere-Ocean Dynamics, Academic Press, 1982.

James, I., N., Introduction to Circulating Atmospheres, Cambridge University Press, 1995.

Pedlosky, J., Geophysical Fluid Dynamics, 2nd Ed., Springer,1987.

Pedlosky, J., Waves in the Ocean and Atmosphere, Springer, 2003.

Piexotto, J. P., and A. H. Oort, Physics of Climate, Springer-Verlag, 1992.

Salby, M. L., Fundamentals of Atmospheric Physics, Academic Press, 1997.

Salmon, R., Lectures on Geophysical Fluid Dynamics, Oxford University Press, 1998.

 The online AMS Glossary of meteorology provides some very good definitions and descriptions of atmospheric terms, and definitely worth examining if you are stuck on some specific terms.

The following research papers extend the class material and provide a useful historical background for some of the key topics. Most of these are available on-line, or indeed on this page above. See me for copies of more difficult to find paper.

Andrews, D. G., and M. E. McIntyre, Planetary waves in horizontal and vertical shear - generalized Eliassen-Palm relation and mean zonal acceleration, J. Atmos. Sci., 33, 2031-2048, 1976.

Charney, J. G., The dynamics of long waves in a barolinic westerly current. J. Meteorol., 4, 135-162, 1947.

Charney, J. G., On the scale of atmospheric motions, Geogysike Publikasjoner, 17(2), 1-17, 1948.

Charney, J. G., and P. G. Drazin, Propagation of planetary scale disturbances from the lower into the upper atmosphere. J. Geophys. Res., 66, 83-110, 1961.

Charney, J. G., and M. E. Stern, On the instability of internal baroclinic jets in a rotating atmosphere. J. Atmos. Sci., 19, 159-179, 1962.

Eady, E. T., Long waves and cyclone waves. Tellus, 1, 33-52, 1949.

Edmon, H. J., B. J. Hoskins and M. E. McIntyre, Eliassen-Palm cross-sections for the troposphere. J. Atmos. Sci., 2600-2616, 1986.

Grose, W.L., and B. J.  Hoskins, Influence of orography on large-scale atmospheric flow. J. Atmos. Sci., 36, 223-234, 1979

Hadley, G. 1735. Concerning the cause of the general trade winds. Phil. Trans. Roy. Soc., 29, 58-62.

Haynes, P. H., and M. E. McIntyre, On the evolution of vorticity and potential vorticity in the presence of diabatic heating and fractional or other forces. J. Atmos. Sci., 44, 1987.

Held, I..M., and A. Y. Hou, Non-linear axially-symmetric circulations in a nearly invicid atmosphere. J. Atmos. Sci., 37, 515-533, 1980.

Held, I. M.,  and T. Schneider, The surface branch of the zonally averages mass transport circulation in the troposphere J. Atmos. Sci., 1688-1697, 1999.

Hoskins, B. J., M. E. McIntyre and A. W. Robertson, On the use and significance of isentropic potential vorticity maps. Quart. J. Roy. Met. Soc., 111877-946, 1985. Part 1 Part 2 Part 3

Lindzen, R.S. and A. Y. Hou, Hadley circulations for zonally averages heating centered off the equator. J. Atmos. Sci, 45, 2416-2427, 1988

Phillips, N., The general circulation of the atmosphere: A numerical experiment. Quart. J. Roy. Met. Soc., 82, 123-164, 1959.

Randel, W. J., and I. M. Held, Phase speed spectra of transient eddy fluxes and critical layer absorption. J. Atmos. Sci., 48, 688-697, 1991.

Schneider, T., The general circulation of the atmosphere, Annual Review of Earth and Planetary Sciences 34: 655-688, doi:10.1146/annurev.earth.34.031405.125144

Tanaka D., T. Iwasaki, S. Uno S, et al., Eliassen-Palm flux diagnostics based on isentropic representation. J. Atmos. Sci., 61, 2370-2383, 2004.

Web pages

•  Dynamics demonstrations from John Hart's fluid dynamics lab.
• The AMS Glossary of meteorology - definitions and descriptions of common terms
• COLA Weather and Climate Data - Daily analysis and forecast maps
• NCEP Reanalysis - weather and climate data home page
• NCEP Reanalysis atlas - more ways of viewing and analyzing NCEP data
• Chris Godfrey's NCEP Reanalysis Page - nice and simple NCEP plots
• NOAA CPC Stratosphere - weather and climate in the stratosphere
• IRI Data Library - various climate data sets with plotting