Theoretical studies of low frequency and seasonal weather variability; dynamical properties of observational and general circulation model (GCM)-generated records; effects of the hydrologic cycle and latent heat release on extratropical weather; and Earth-system science studies are summarized

Ebisuzaki, Wesley

Maasch, Kirk A.

Oglesby, Robert

Pandolfo, Lionel

Saltzman, Barry

Tang, Chung-Muh

English

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Title: Application of Dynamical Systems Theory to Global Weather Phenomena
Revealed by Satellite Imagery
Investigators:
Barry Saltzman (PI)
Wesley Ebisuzaki (Post-Doctoral Assoc.)
Kirk A. Maasch (Graduate Student)
Robert Oglesby (Graduate Student)
Lionel Pandolfo (Graduate Student)
Yale Department of Geology and Geophysics
P.O. Box 6666, New Haven, CT 06511
N90 12 063
Chung-Muh Tang
Universities Space Research Association
The American City Building, Suite 311
Columbia, MD 21044
Significant Accomplishments in the Past Year:
I) Theoretical studies of low frequency and seasonal weather vari-
ability. As part of our effort to treat extratropical weather in
terms of stochastic-dynamical systems analysis, we have developed a
thermally-forced, low-order model of the atmosphere that seems capable
of accounting for many of the statistical properties of the long-wave
structure including the main seasonal and planetary-monsoonal varia-
tions. In its most simplified form this model can be reduced to a 3-
variable forced, dissipative dynamical system exhibiting a "folded
resonance" equilibrium structure that admits multiple steady-states
in a realistic parameter range. This structure can explain the ob-
served bimodality and vacillation of long-wave amplitude in winter
and the more steady monsoonal circulation characteristic of summer
(Saltzman, Tang, and Maasch). In other theoretical studies the cri-
teria for "baroclinic adjustment" and the role of interactions between
planetary and cyclone-scale waves in accounting for the observed zonal
mean and wave structure have been elucidated in a series of three
papers (Ebisuzaki).
2) Dynamical properties of observational (e.g., satellite) and GCM-
generated records. The newly developed techniques for determining
"attractor dimensionality", and the presence of multiple regimes and
"jump" phenomena have been used and improved in a series of studies
applied initially to paleoclimatic data (Maasch). The ultimate aim is
to apply th_se same techniques to the long, continuous time-series
being made available for the first time by satellite borne instrumen-
tation, and being made available theoretically by extended GCM runs.
A first order task is to determine the extent to which those series
can be ascribed to an identifiable deterministic process (that may how-
ever be "fractal" or "chaotic"),having an attractor that can be model-
led by a low-order system. Our preliminary results, for example, indi-
cate that the weather variability exhibited by a complex GCM can be
modelled with a reduced low-order system containing a minimum of six
variables (Haasch and Saltzman).
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3) Effects of the hydrologic cycle and latent heat release on extra-
tropical weather. Using a general circulation model we have determined
that extratropical Northern Hemisphere weather is extremely sensitive to
variations of sea surface temperatures in the Gulf of Mexico which is
the most significant source of water vapor fueling the latent heat re-
lease in the North Atlantic storm track. The consequences of the cool-
ing of this Gulf region during the deglaciation phase of the last ice
age cycle, about 10,000 years ago, are corroborated by the geologic and
paleoclimatic evidence available for this period (Oglesby, Maasch, and
Saltzman).
4) Earth-system science studies. In a series of papers we have explored
the degree to which the major changes in terrestrial climate associated
with the Pleistocene "ice ages" can be accounted for internally by com-
plex nonlinear interactions involving the atmosphere, bio-hydrosphere,
and cryosphere. In our most recent contribution we show how positive
feedback in the global carbon cycle, as controlled by the deep ocean
state, can provide the instability to drive the major ice age cycle.
When additive external forcing (e.g., due to earth-orbital, Milanko-
vitch variations) is applied much of the inferred global variations of
climate over the past 2 million years, including the "jump" about
900,000 years ago, can be accounted for with a relatively small number
of adjustable parameters (Saltzman and Maasch).
Focus of Current Research and Plans for Next Year:
I) Continuing Study of Low-Order Weather Systems. We are presently
performing numerical calculations to explore the robustness of the
results of our 3-variable model described above for a full range of
parameters. Our objective will be to establish the relevance of the
results of this thermally-forced model as an explanation of the ob-
served bimodality of the long-wave amplitude structure. In addition,
the model will be expanded by the successive addition of new features
such as wave-wave interactions and orographic forcing. Concerning
the former additional considerations, Dr. W. Ebisuzaki will be con-
tinuing his promising numerical modelling work on baroclinic adjust-
ment and the interactions of planetary and cyclone scale wave motions;
interesting work on the latter, orographic, considerations is already
underway by Lionel Pandolfo,in the contexts of both barotropic and
baroclinic models. Furthermore, it remains our goal to include hydrol-
ogy and clouds into these low-order models in order to connect these
models more directly with satellite observations.
2) Observational studies. Dimension analysis of satellite OLR and
cloud records are being pursued, in conjunction with similar analyses
of the output of general circulation models. A more general observa-
tional goal will be to use satellite data to help quantify the "cloud
and latent heat forcing" in the storm tracks associated with the long
baroclinic waves, as embodied qualitatively in our present low-order
dynamical model.
14
Publications Since June 1987:
I) Tang, C.-M., 1988: The meridional scale of baroclinic waves with latent
heat release. Atm6sfera , I, (in press).
2) Saltzman, B. and C.-M. Tang, 1988: Folded resonance and seasonal vacil-
lation in a thermally-forced baroclinic wave model (abstract). Ann.
Geophysicae, European Geophysical Society, XIII General Assembly,
Bologna, p. 107.
3) Ebisuzaki, W., 1988: Dynamical criterion for a marginally-unstable,
quasi-linear behavior in a two-layer model. J. Atmos. Sci., 45,(in
press).
4) Maasch, K.A., 1988: Statistical detection of the mid-Pleistocene tran-
sition. Climate Dynamics, 2, 133-143.
5) Maasch, K.A., 1988: Dimension from a time series: application to deep
sea 6180 records (abstract). EOS, 69, 376.
6) Saltzman, B. and K.A. Maasch, 1988: Carbon-cycle instability as a
cause of the late-Pleistocene ice-age oscillations: modelling the asym-
metric response. Global Biogeochem. Cycles, 2, (in press).
7) Saltzman, B., 1988: Modelling the slow climatic attractor. Physically
Based Modeling and Simulation of Climate and Climatic Change (M.E.
Schlesinger, ed.), Reidel Publ. Co., Dordrecht (in press).
Manuscripts Submitted for Publication or in Preparation
I) Saltzman, B., C.-M. Tang, and K.A. Maasch, Folded resonance and seasonal
vacillation in a thermally-forced baroclinic wave model. (submitted for
publication).
2) Ebisuzaki, W., Interactions between long and synoptic-scale waves: Part
I. Instibility of a non-zonal flow. (submitted for publication).
3) Ibid., Part II. Growth rate of long waves. (submitted for publication).
4) Maasch, K.A., On the practicality of calculating dimension from 8180
records. (in preparation).
5) Pandolfo, L. and A. Sutera, The effects of form-drag and wave-wave inter-
actions on the equilibrium solutions of topographically-forced barotropic
and baroclinic models of atmospheric planetary waves. (in preparation).
6) Oglesby, R., K.A. Maasch, and B. Saltzman, Glacial meltwater cooling of
the Gulf of Mexico: GCM implications for Holocene and present-day cli-
mates. (submitted for publication).
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Application of dynamical systems theory to global weather phenomena revealed by satellite imagery

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