Table Of ContentDynamics, Transport and Photochemistry in
the Middle Atmosphere of the Southern Hemisphere
NATO ASI Series
Advanced Science Institutes Series
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Series C: Mathematical and Physical Sciences -Vol. 321
Dynamics, Transport and
Photochemistry in
the Middle Atmosphere of
the Southern Hemisphere
edited by
Alan O'Neill
Hadley Centre for Climate Prediction and Research,
Meteorological Office, Bracknell, UK
Kluwer Academic Publishers
Dordrecht / Boston / London
Published in cooperation with NATO Scientific Affairs Division
Proceedings of the NATO Advanced Research Workshop on
Dynamics, Transport and Photochemistry in the Middle Atmosphere of the Soutern
Hemisphere
San Francisco, California, U.S.A.
April 15-17, 1989
Library of Congress cataloglng-In-Publlcatlon Data
NATO Advanced Research Workshop on Dyna~ics. Transport. and
Photochemlstry in the Middle Atmosphere of the Southern Hemlsphere
(1989 San Francisco, Calif.)
Dynamlcs. transport. and photochemistry in the m,ddle atmosphere
of the Southern Hemisphere: proceedings of the NATO Advanced
Research Workshop on Dynamics, Transport, and Photoche~istry in the
Middle atmosphere of the Southern Hemisphere, San Francisco,
Cal ifernia. U.S.A., 15-17 April, 1989 I edited by Alan D'Nei 11.
p. cm. -- (NATD ASI series. Series C, mathematical and
physical sciences; v. 321)
Includes indexes,
i. Middle at~eSphere--Southern Hemisphere--Congresses. 2. Dynamic
meteorology--Congresses. 3. Photochemistry--Congresses.
1. O' Ne i 1. A1 a n, 1950- II. Tit 1e . I II. Se r i e S .
OC881.2.M53N37 1989
551.5' 1--dc20 90-5315
ISBN-13: 978-94-010-6797-3 e-ISBN-13: 978-94-009-0693-8
DOl: 10.1007/ 978-94-009-0693-8
Published by Kluwer Academic Publishers,
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TABLE OF CONTENTS
Preface •••••••••••••••••••••••••.••••••••••••••••••••••••••••••.•. vi i
Middle atmosphere dynamics and transport: some current challenges to
our understanding/M.E. McINTYRE •••••••••••••••••••••••••••••••••.••• l
On data sources and quality for the southern hemisphere
stratosphere/D/J. KAROLY and D.S. GRAVES ••••••••••••••••••••••••••• 19
The seasonal evolution of the extra-tropical stratosphere in the
southern and northern hemispheres: systematic changes in potential
vorticity and non-conservative effects of radiation/A. O'NEILL and
V.D. POPE ••••••••••••••••••••••••••••••••.••.•••••••••••••••••••••• 33
The final warming of the statosphere/C.R. MECHOSO .•••.••••••••••••• 55
Comparison of the Southern Hemisphere springs of 1988 and
1987/P.A. NEWMAN, M.R. SCHOEBERL and L.R. LAIT •••••.••••••••••••••. 71
A comparison of the dynamic life cycles of tropospheric medium
scale waves and stratospheric planetary waves/W.J. RANDEL ••.•••.••• 91
Traveling planetary waves in the middle atmosphere/I. HIROTA •••.•• lll
Dynamical properties of the Antarctic circumpolar vortex inferred
from aircraft observations/D.L. HARTMANN .•••••••••••.••••••••••••• 117
Large stratospheric sudden warming in Antarctic late winter and
shallow ozone hole in 1988: observation by Japanese Antarctic
research expedition/H. KANZAWA and S. KAWAGUCHI •••••••••••••••..•. 135
A possible influence of sea surface temperature variation on the
recent development of ozone hole/K. KODERA and K. YAMAZAKI ••••..•• 149
Gravity Waves in the Southern Hemisphere Middle Atmosphere:
A Review of Observations/R.A. VINCENT ••.••••••••••..•..••.•..••••• 159
Gravity waves in the middle atmosphere of the southern
hemisphere/D.C. FRITTS ••••••••.••••.•.••..••••••••••.••.•••••...•• 171
Nitrogen chemistry in Antarctica: a brief review/So SOLOMON ••••.. 191
The potential role of HOx and Cl0x interactions in ozone hole
photochemistry/P.J. CRUTZEN and C. BRliHL ••••••••••.•••••••••••..•• 203
Ozone transport in the southern hemisphere/K.K. TUNG and H. YANG •• 213
Future observations of the middle atmosphere/J.C. GILLE •.••••.•.•• 217
Modelling and observations: the use of diagnostics/D.G. ANDREWS •• 227
Antarctic ozone depletion and potential effects on the global ozone
budget/W.L. GROSE, R.S. ECKMAN, R.E. TURNER, and W.T. BLACKSHEAR •• 237
Alphabetical index of authors ••••••••••••••••••••••••••••••••••••• 253
Subj ect index •••••••.•••.•••••••••••••.••••..••.•••••.••••••••••.• 255
PREFACE
The NATO Advanced Research Workshop on "Dynamics, Transport am.
Photochemistry in the Middle Atmosphere of the Southern Hemisphere"
was held in San Francisco, California, U.S.A., 15-17 April 1989. In
addition to NATO, the workshop was supported by the University of
California, Los Angeles, and by the National Aeronautics and Space
Administration, U.S.A. (NASA). The American Meteorological Society
was a co-operating organization. The venue for the workshop was the
Lone Mountain Conference Center of the University of San Francisco.
The workshop was organized and directed by Dr A.O'Neill (Hadley Centre
for Climate Prediction and Research, Meteorological Office, Bracknell,
U.K.) and Prof C.R. Mechoso (Dept of Atmospheric Sciences, University
of California, Los Angeles, U.S.A.).
The workshop was the third one held as part of the Middle
Atmosphere in the Southern Hemisphere (MASH) project, an international
effort (under the auspices of the Middle Atmosphere Program) to learn
more about dynamics, transport and photochemistry in the middle
atmosphere of the southern hemisphere. Before the discovery that,
during recent years, a dramatic thinning of the ozone layer takes
place over Antarctica in spring - the "ozone hole" - the middle
atmosphere of the southern hemisphere had received much less attention
than that of the northern hemisphere from meteorologists and
atmospheric chemists. The MASH project was instituted to remedy this
comparative lack of interest.
The workshop was organised around four sessions of invited papers
given by leading atmospheric scientists. Ample time was allowed for
in-depth discussions after the formal presentations. Most of the
papers are included in these proceedings. I decided not to divide the
volume into separate sections on dynamics, transport and
photochemistry in order to encourage interdisciplinary reading, and
also to mirror the interdisciplinary nature of the workshop. Several
of the papers would not fit naturally under one heading.
Support was provided by NATO through Dr C Sinclair of the
Scient1fic Affairs Division. His courteous advice is much
appreciated. Support from UCLA came through Dr. C.A. Hall Jr., and
from NASA (NAGW-1021) through Dr M.J. Prather. Dr J.D. Farrara helped
with the organisation, and Dr V.D. Pope gave editorial assistance.
Patient encouragement from Mrs Nel de Boer (Kluwer) stimulated my
efforts to coax manuscripts from busy scientists. I am especially
grateful to Prof. C.R. Mechoso, ably assisted by Mrs C. Wong, whose
organisational skills were essential to the success of the workshop.
Finally, I would like to thank the invited speakers and participants
for making the workshop not only scientifically stimulating but also
most enjoyable.
Brac kne 11 , U.K. Alan O'Neill
25 June
19~
vii
MIDDLE ATMOSPHERIC DYNAMICS AND TRANSPORT:
SOME CURRENT CHALLENGES TO OUR UNDERSTANDING
MICHAEL E. McINTYRE
Department of Applied Mathematics and Theoretical Physics
Silver Street, Cambridge CBS 9EW
U. K.
ABSTRACT. The fluid dynamics of wave propagation, wave breaking, and the resulting tur
bulence - be it the fully three-dimensional small-scale turbulence due to breaking internal gravity
waves, or the layerwise two-dimensional turbulence due to breaking Rossby waves - poses three
major challenges to research on middle atmospheric dynamics and chemical transport. These are,
first, the unjustifiability of the eddy-diffusivity concept, under conditions often met with in the
atmosphere, second, the ill-understood nature of the Rossby-wave-associated dynamical feedbacks
on the global circulation and, third, an acute difficulty in parameterizing vertical mixing by con
vectively overturning gravity waves in the mesosphere and lower thermosphere.
1. Introduction
The three major challenges I have chosen to discuss are all related to a tendency for
naturally-occurring turbulence to be spatially inhomogeneous. This often gives rise to
situations very different from the situations assumed in classical turbulence theory.
One of the contributing factors seems to be the importance of various kinds of wave propa
gation mechanism. Besides leading to the propagation of information, angular momentum,
etc., between different parts of the atmosphere, the dynamical restoring mechanisms to
which the waves owe their existence can act locally to suppress turbulent motion, often in
a spatially very selective way. Indeed one often has the impression of dealing with closely
adjacent, strongly interacting regions of wavelike motion and turbulent motion, a kind of
highly inhomogeneous 'wave-turbulence jigsaw puzzle' in which the waves strongly modify,
indeed often give rise to, the turbulence, and in which the turbulence, in turn, modifies the
local spatial distribution of the wave restoring mechanism, and also, after a propagation
delay, the wave field at greater distances. The word 'turbulence' is being used here in the
broad sense that includes not only three-dimensional turbulence - such as that due to cu
mulus convection, to boundary-layer friction, to Kelvin-Helmholtz instability or to breaking
internal gravity waves - but also layerwise two-dimensional turbulence, such as that due to
baroclinic instability or to breaking Rossby waves.
The first of the three challenges to be discussed is that posed by the concept of the
'eddy diffusivity' of materially conserved quantities such as long-lived tracer substances (§3
below). Although that concept correctly expresses the statistical tendency for such tracers
to move downgradient, in some long time averag~ sense - and will, inevitably, continue to
be used faute de mieux as a modelling device for some time to come - we cannot be too
careful about the use we make of the concept. Model predictions that depend on it too
heavily need to be regarded with suspicion. This is because the conditions under which
1
A. O'Neill (ed.),
Dynamics, Transport and Photochemistry in the Middle Atmosphere a/the Southern Hemisphere, 1-18.
© 1990 Kluwer Academic Publishers.
2
it can be strictly justified in terms of classical turbulence theories, namely spatial near
homogeneity of the turbulence, seldom appear to be met, for the reasons just mentioned.
For some purposes the concept may actually be wrong qualitatively, in the sense that fluxes
are not even roughly proportional to mean gradients. The Antarctic ozone hole provides
one of the more conspicuous examples of this. Various other paradoxes arise, as will be
pointed out. There is also the simple but potentially important fact that current models
of chemical evolution assume that chemical constituents interdiffuse and react when, in
reality, they may well be separate and non-reacting in a fully-resolved, fine-grain view (e.g.
Tuck 1979).
The second challenge is how to parameterize global-scale dynamical feedbacks in sim
plified general circulation models, particularly the feedbacks associated with the Rossby
wave-associated or layerwise two-dimensional phenomena that appear to dominate events
in the lower and middle stratosphere. It is widely recognized that there will be a continuing
need for simplified circulation models to aid the assessment of multidecadal ozone-climate
scenarios. Furthermore, research on the feedback mechanisms will be an important means,
in its own right, of improving our understanding of what is robust, and what is sensitive, in
the complicated web of causal links involved. There has been no spectacular progress over
the past few years, as far as I know, and so the present discussion (§4 below) will confine
itself to a very brief update on the lengthier discussion given in a previous informal review
and forward look, written for the proceedings ofthe Erice Workshop (Mcintyre 1987, here
after E87). Progress on this extremely difficult set of problems, which are not unrelated
to some of the problems to be discussed in §3, seems likely to depend on continued efforts
to combine theoretical insights with ultra-high-resolution numerical modelling as well as
with observational information. On the observational side, the proposed new generation of
space-based wind sounders and high-resolution scanning limb sounders should in due course
provide a particularly important source of new information.
It seems more certain than ever that the strange quantity known as potential vortic
ity will playa central role in the quest for an improved understanding of the global-scale
dynamical feedbacks, and that it will also be important for future attempts at the simul
taneous retrieval of dynamical and chemical information from future observing systems,
and in the quality control of observational data processing. As a preliminary to §§3 and
4, therefore, §2 briefly recalls some of the fundamental properties of PV, including its rele
vance to wave-mean interaction theory and the differences between PV and chemical-tracer
behaviour.
The third challenge (§5) concerns what may be an even tougher part of the global cir
culation and transport problem, albeit that its most critical importance appears likely, on
present knowledge, to be confined to mesospheric and higher altitudes. This is the prob
lem of how to parameterize the vertical turbulent mixing by convectively breaking internal
gravity waves in the mesosphere and lower thermosphere. Such mixing seems likely to be
important in summertime, for instance, in transporting atomic oxygen downward against
the mean circulation (e.g. Thomas et al. 1984, Garcia and Solomon 1985). The turbulence
is, again, highly inhomogeneous, but interestingly enough it seems possible that the no
tion of eddy diffusivity might be justifiable to some extent in a non-classical way, for this
purpose. However, it can also be shown that there is still no such thing as a single eddy
diffusivity that is applicable for all purposes, and that the tacit assumption that there is
such a thing as 'the' eddy diffusivity, which one often encounters in the literature, is still
highly dangerous.
Another feature of the problem seems to be a pathological sensitivity of the efficiency of
vertical mixing to the precise degree of wave supersaturation. In particular, convectively-
3
breaking gravity waves seem likely to be inefficient at vertical mixing unless they break very
violently indeed, so as to give a very large supersaturation, or amplitude overshoot. Again,
the discussion will be kept very brief since most of the ground has already been covered
elsewhere (McIntyre 1989b). Breaking gravity waves provide, also, a particularly striking
illustration of the aforementioned differences between PV and chemical-tracer behaviour
- differences which can be shown to be of central importance, qualitatively as well as
quantitatively, to our understanding of the global circulation.
2. The fundamental properties of potential vorticity
We recall these only briefly since they have been discussed extensively elsewhere (Hoskins
et al. 1985; Haynes and McIntyre 1987, 1990; McIntyre and Norton, 1990). The most
accurate and general version of the potential-vorticity concept, for a continuously stratified
fluid, is that associated with the exact set of definitions given by Ertel (1942). A hydrostatic
version was given slightly earlier by Rossby (1940). The difference between the exact and
hydrostatic versions is usually unimportant in atmospheric dynamics, the main exception
being when one seeks to understand in detail how the potential vorticity is affected by three
dimensional turbulent mixing. The exact (Ertel) definition is usually taken for convenience
as
(1)
where p is the mass density, qa the three-dimensional absolute vorticity, including the
vorticity of the earth's rotation, V the three-dimensional gradient operator with respect to
geometric position x, and fJ the potential temperature. As Ertel pointed out, it would be
equally valid in principle to adopt any of an infinite number of other definitions in which fJ
is replaced by some monotonic function of fJ. For convenience we shall refer to Q, as defined
by (1), as 'the' potential vorticity, hereafter 'PV'. There are three main points about Q.
2.1. MATERIAL TENDENCY, AND VISUALIZABILITY
The first is the well known fact that the PV is materially conserved if diabatic heating
and nonconservative forces are negligible. This is a particular case of the general result
(2)
where the material derivative, and the nonadvective flux or transport, are defined respec
tively by
D/Dt=8/8t+u·V, NQ = -Hqa - F X VfJ , (3a, b)
u being the three-dimensional velocity field, F the viscous or other nonconservative body
force per unit mass, and H the diabatic heating rate expressed as the material rate of change
of fJ. To the extent that the right-hand side of (2) is effectively small, the PV becomes
approximately an air-mass marker, making its evolution easy to grasp conceptually, and
easy to visualize in terms of isentropic distributions of PV, that is, in terms of layerwise
two-dimensional distributions of PV on constant-fJ surfaces.
