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
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.
Hartmann, D.L., 1994: Global Physical
Climatology.
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.
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.