ATMS 545         The General Circulation       Spring Quarter, 2007

 

Instructor

J.M. Wallace 543-7390; 504 ATG; wallace@atmos.washington.edu

 

Synopsis

Partitioning of global fields into zonal mean versus eddy and time mean versus transient components.  Concept of available potential energy  and the kinetic energy cycle.  Balance requirements for angular momentum, energy and mass.  Dynamics of the zonally symmetric component of the general circulation.  Distinction between Eulerian- and Lagrangian-mean circulations.  The Eliassen-Palm flux.  Energetics and life cycle of baroclinic waves, and their interaction with the background flow.  Maintenance of the climatological-mean circulation.  Structure and dynamics of low-frequency fluctuations about the climatological mean.   Application of the above concepts to explaining the annual march of tropospheric wind systems, the climate of the stratosphere, the atmospheric response to El Niño, the Pacific / North American pattern, and the annular modes.

 

Rationale

The course (1) describes the major global wind systems and the dynamical processes that maintain them; (2) applies the quasi-geostrophic equations and other basic dynamical formalisms taught in dynamics courses to phenomena in the real atmosphere; (3)  introduces some of the techniques commonly used in diagnosing global observations and climate simulations; (4) offers a historical overview of the development of our current ideas concerning the nature and theory of the general circulation (5) introduces the global atmospheric datasets used in general circulation research; and (6) provides some examples of the role of the atmospheric general circulation in climate dynamics.  The course is best taken as a sequel to ATMS 509 and 542, but is designed to be comprehensible to  students with limited background in atmospheric dynamics who wish to gain an appreciation of the role of the atmospheric general circulation in climate and the long range transport of trace substances.

 

Course Format

Lectures: the style is informal and questions and comments are invited.  Students are evaluated on the basis of midterm and final exams (20 and 30%, respectively) and a ~2500-wd. term paper on an approved topic selected by the student (40%).  Course notes are provided and students are encouraged to read a set of influential journal articles.

 

Tentative Schedule by Week

1.         Overview, historical background, datasets, space/time averaging formulation.

2.         The kinetic energy cycle, thermally direct vs. thermally indirect circulations.

3.         Angular momentum balance, relation to length of day, roles of eddy fluxes and mean meridional circulations.

4.         Total energy balance and its relation to net radiation, role of eddy fluxes in the poleward transport of energy, the hydrologic cycle.

5.         Dynamics of the zonally symmetric component of the general circulation.

6.         Eulerian- versus Lagrangian-mean meridional circulations; the Eliassen-Palm flux, application to stratospheric warmings.

7.         Diagnosis of time-mean flow including the climatological-mean planetary waves and the monsoons.

8.         Baroclinic waves: structure, energetics, life cycle, interaction with the zonally symmetric flow.

9.         Case studies: the annual march, ENSO.

10.       Case studies: the quasi-biennial oscillation, blocking, annular modes.

 

Some Recommended Reading

Books

Andrews, D.G., J. R. Holton and C. B. Leovy, 1987: Middle Atmosphere Dynamics.  Academic Press, 488 pp.

Grotjahn, R., 1993:  Global Atmospheric Circulations.  Oxford University Press, 430 pp.

Hartmann, D.L., 1994: Global Physical Climatology. Cambridge University Press, 411 pp.

Hoskins, B.J. and R.P. Pearce, 1983:  Large Scale Dynamical Processes in the Atmosphere.  Academic Press, 1983, 397 pp.

James, I.N., 1994:  Introduction to Circulating Atmospheres.  Cambridge University Press, 422 pp.

Lorenz, E.N., 1967: On the Nature and Theory of the General Circulation of the Atmosphere, WMO (out of print but I have a copy) p. 59-96 (historical background starting with Halley).

Manabe, S., 1985:  Issues in Atmospheric and Oceanic Modeling.: Part A: Climate Dynamics.  Academic Press, 591 pp.

Peixoto, J. and A. H. Oort, 1992: The Physics of Climate, American Inst. of Physics, New York, 520 pp.

Wallace, J.M. and P.V. Hobbs, 2nd edition, 2007: Atmospheric Science:  an Introductory Survey. Academic Press, Chapter 10.

 

Early Articles

Starr, V.P.  1948: On the production of kinetic energy in the atmosphere.  J. Meteorology, 5, 193–196.

Starr, V.P., 1948:  An essay on the general circulation of the Earth's atmosphere.  J. Meteorol., 5, 39–43.

Palmen, E., 1949:  Meridional circulations and the transfer of angular momentum in the atmosphere.  J. Meteorol., 6, 429–430.

Starr, V.P., 1949: Reply.  J. Meteorol., 6, 430.

Priestly, C.H.B., 1949:  Heat transport and zonal stress between latitudes.  Quart. J. R. Meteorol. Soc., 75, 28–40.

Eliassen, A., 1952: Slow thermally or frictionally controlled meridional circulation in a circular vortex.  Astrophysica Norvegica, 5, 19–60.

Lorenz, E.N. 1955:  Available potential energy and the maintenance of the general circulation.  Tellus, 7.

Kuo, H.-L., 1956:  Forced and free meridional circulations in the atmosphere.  J. Meteor., 13, 561–568.

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