Saltzman B. (editor) Anomalous Atmospheric Flows and Blocking
Подождите немного. Документ загружается.
294
J.
S.
FREDERIKSEN
FORCED DRAG DIFFUSION
0
2
4
6
8
10 12
14
16
18
x)
Wavenumber
m
FIG.
8.
Disturbance kinetic energy
spectra
as
function of zonal wavenumber
m
and day
for
a
IO-day
period.
tend to predominate in the largest scales after sufficient time, irrespective
of
whether the errors are generated by model differences (Fredenksen and
Sawford,
1980,
Figs.
9
and
10,
and references therein; Bengtsson and Lange,
1982)
or
by differences in initial conditions
as
in Fig.
8.
4.3.
Disturbance Stream functions
The disturbance streamfunctions at days
2,4,6,
and
10
and at
t~
=
0.7
are
shown in
Fig.
9.
Figure
10
shows the disturbance streamfunction at
0
=
0.1
on days
6
and
10.
Although it
is
not shown explicitly in these diagrams, we
note that the disturbance
starts
as
a rather shallow structure in the Atlantic
and Pacific Oceans, with largest amplitude at the lowest level, and during the
integration penetrates increasingly into the upper troposphere. In addition,
there
are a number
of
new areas
of
development that
occur
during the 10-day
INSTABILITY THEORY AND NONLINEAR EVOLUTION
295
period. The shift in the maximum of the disturbance amplitude is in fact
qualitatively similar to that found in corresponding nonlinear experiments
of disturbances growing on zonally averaged basic flows (Gall,
1976;
Sim-
mons and Hoskins,
1978;
Frederiksen,
198
la,b).
Next we consider in more detail the synoptic sequence of events shown in
Figs.
9
and
10,
concentrating mainly on the two levels shown there. We
mention, however, that at
cr
=
0.9
more of the smallest scale features are
visible, while only the largest scale features tend to penetrate to
cr
=
0.1.
On
day
1
(not shown) there are the first indications of slight poleward move-
ments
of
the anticyclones and equatorward movements of the cyclones in
both the Pacific and Atlantic sectors. Further, there are the beginnings of
development of a cyclone over the Himalayas, with an associated weaker
FIG.
9.
Disturbance streamfunction on (a) day
2,
(b) day
4,
(c) day
6,
and (d) day
10
at
CT
=
0.7.
296
J.
S.
FREDERIKSEN
FIG.
9b.
See
legend
on
p.
295.
anticyclone. These features are even more pronounced on day
2,
as seen
from Fig.
9.
In fact, at
Q
=
0.3
(not shown), the splitting has yielded an
anticyclone over Greenland with lows both upstream and downstream.
The developments that occur in the early stages appear to have the follow-
ing causes. First,
in
the Pacific and Atlantic sectors one is seeing the begin-
nings of development of dipoles
or
multipoles. In general terms, these may
be
regarded
as
the nonlinear analog of modes like the Pacific, and in particu-
lar Pacific and Atlantic, onFt-of-blocking dipole modes shown in Figs.
6
and
7
of Frederiksen
(
I982a) and in our Figs.
3
and
4.
Second, in the Tibetan and
Greenland areas the large-scale
flow
changes during the first few days largely
through the presence of drag and nonlinear interactions. These changes in
turn mean that the new (unbalanced) large-scale flow impinges on the topog-
raphy to produce new disturbances. These disturbances then project onto (or
INSTABILITY THEORY AND NONLINEAR EVOLUTION
297
FIG.
9c.
See
legend
on
p.
295.
may be expanded in terms of) growing, neutral, and decaying modes, with
the growing modes playing the most important role, as may be seen from the
amplification that occurs during the integration period. Among the (nonlin-
ear analog of) growing instability modes that would make contributions to
the disturbances are modes like the Pacific and Atlantic onset-of-blocking
dipole mode in Fig. 7 of Frederiksen (1982a), the intermediate mode in Fig. 7
of Frederiksen
(1
983b), and mature modes like the North Atlantic Oscilla-
tion mode in Fig.
5
of Frederiksen (1983b).
On day
4
the disturbance still has a significant westward tilt with height in
most regions (not shown), indicating that baroclinic processes are making a
substantial contribution in the developments. By day
4
we see the beginnings
of wave trains from the North Atlantic-Greenland sea region across the
northern Soviet Union into northeast Asia and from North Africa across
298
J.
S.
FREDERIKSEN
Arabia into central Asia. A further wave train is beginning to form across the
United States and goes into the Atlantic Ocean. The signature
of
the onset-
of-blocking dipole modes is also seen in the momentum fluxes (Fig. 9 of
Frederiksen and Pun, 1985), which, particularly at higher levels, have multi-
ple centers
of
poleward and equatorward fluxes in the Atlantic and Pacific,
leading to convergence and divergence zones. This is a characteristic of the
onset-of-blocking modes as shown in Fig.
9
of Frederiksen (1982a) and in
Fig.
1Oc
of
Frederiksen (1984). It is interesting to note that Ji and Tibaldi
(1983) also find that during the early stages of block development their
observed latitudinal distribution
of
momentum flux also shows convergence
and divergence zones, indicating the buildup of separate branches of the jet.
By day
6
there has been a considerable intensification ofthe anticyclone in
INSTABILITY THEORY AND NONLINEAR EVOLUTION
299
the North Atlantic -Greenland sea area at all levels. We note the high merid-
ional wavenumber of the disturbance in the Pacific Ocean, particularly at
=
0.7.
There has
also
been marked intensification of the disturbance in the
North Africa- Arabia and North America- West Atlantic area, with some
downstream propagation between days
4
and
6.
At
this stage, the wave train
emanating from the Tibetian region has effectively merged with the Pacific
wave train. In the North Atlantic- Arctic region we see the emergence of the
North Atlantic Oscillation pattern. This is disguised to some extent at the
lower levels by the presence of small-scale features and is best seen at the very
highest model level of
0
=
0.1 shown in Fig. 10a. In the North Atlantic-
Arctic region there is quite reasonable agreement between Fig.
1
Oa and the
North Atlantic mature anomaly instability mode in Fig.
6,
which was found
to be quite similar to the North Atlantic Oscillation
of
van Loon and Rogers
300
J.
S.
FREDERIKSEN
FIG.
lob.
See
legend
on
p.
299.
(
1978). Their sea level pressure pattern is, however, a larger scale pattern due
to averaging over many years, which removes the smaller scale features and
resembles more the
CJ
=
0.1
disturbance streamfunction in Fig. 10a rather
than the disturbance at lower levels. There is perhaps some anticlockwise
rotation in Fig.
1
Oa compared with the observations.
There is a reasonable resemblance between the disturbance in the North
Atlantic- Arctic region and the North Atlantic Oscillation pattern obtained
from GCM experiments shown in Fig.
14
and, in particular, in Fig.
22
of Lau
(
198
1
).
We
also
note that the North Atlantic Oscillation pattern of van Loon
and Rogers
(
1978) and
Lau
(
198
1
)
has features in common with some of the
patterns described by other authors. For example, it has common features
with the Atlantic mature anomaly of Dole (1982; Fig. 5.7) of appropriate
sign. We note that,
as
discussed by van Loon and Madden
(1
98
l),
many
of
INSTABILITY THEORY AND NONLINEAR EVOLUTION
30
1
the well-known teleconnection patterns are contained within the compre-
hensive Southern Oscillation pattern (Walker and
Bliss,
1932; Troup,
1965;
Trenberth,
1976;
Trenberth and Paolino,
198
1
;
van
Loon
and
Rogers,
198 1).
ACKNOWLEDGMENTS
It is a pleasure to thank Roberto Benzi for organizing, and IBM Italy for sponsoring, the
workshop on “Global scale anomalous circulation in the atmosphere and blocking” at which
this work was presented.
REFERENCES
Austin,
J.
F. (1980). The blocking of middle latitude westerly winds by planetary waves.
Q.J.R.
Barnett,
T.
P.
(
1984). Variations in near-global
sea
level pressure.
J.
Atrnos.
Sci.
42,478- 50
1.
Bengtsson,
L.,
and Lange, A.
(
1982). Results of the WMO/CAS MWP data study and intercom-
parison project for forecasts for the Northern Hemisphere in 1979-1980. World Meteoro-
logical Organization, Geneva.
Berggren, R., Bolin, B., and Rossby, C.
G.
(1949). An aerological study of zonal motion, its
perturbations and breakdown.
Tellus
1,
14-37.
Blackmon, M. L. (1976). A climatological spectral study of the 500 mb geopotential height
of
the Northern Hemisphere.
J.
Atmos.
Sci.
33,
1607
-
1623.
Blackmon, M. L., Wallace,
J.
M., Lau, N., and Mullen,
S.
L. (1977). An observational study
of
the Northern Hemisphere wintertime circulation.
J.
Atmos.
Sci.
34,
1040- 1053.
Bourke, W.
(
1974). An efficient, one-level primitive-equation spectral model.
Mon.
Weather
Rev.
100,683-689.
Bourke, W., McAvaney, B., Pun,
K.,
and Thurling, R.
(I
977). Global modeling ofatmospheric
flow by spectral methods.
Methods
Comput.
Phys.
17,
267-324.
Colucci,
S.
J.
(1982). Diagnostic studies of atmospheric blocking patterns. Ph.
D.
thesis, State
University of New York at Albany.
Dole, R. M.
(
1982). Persistent anomalies of the extratropical Northern Hemisphere wintertime
circulation. Ph.
D.
thesis, Massachusetts Institute of Technology.
Dole, R. M. (1983). Persistent anomalies ofthe extratropical Northern Hemisphere wintertime
circulation.
In
“Large-Scale Dynamical Processes in the Atmosphere” (B.
J.
Hoskins and
R.
P.
Pearce, eds.). Academic Press, New York.
Frederiksen,
J.
S.
(1979). The effect
of
long planetary waves on the regions of cyclogenesis:
Linear theory.
J.
Atmos.
Sci.
36, 195-204.
Frederiksen,
J.
S.
(1981a). Growth and vacillation cycles of disturbances in Southern Hemi-
sphere flows.
J.
Atmos.
Sci.
38,
1360- 1375.
Frederiksen,
J.
S.
(1981b). Scale selection and energy spectra of disturbances in Southern
Hemisphere flows.
J.
Atmos.
Sci.
38,
2573-2584.
Frederiksen,
J.
S.
(1982a). A unified threedimensional instability theory of the onset ofblock-
ing and cyclogenesis.
J.
Atmos.
Sci.
39,969 -987.
Frederiksen,
J.
S.
(1 982b). Instability of the three-dimensional distorted stratospheric polar
vortex at the onset of the sudden warming.
J.
Atmos.
Sci.
39,2313-2329.
Meteorol.
SOC.
106,
327-350.
302
J.
S.
FREDERIKSEN
Frederiksen, J.
S.
(1983a).
Disturbances and eddy fluxes in Northern Hemisphere flows: Insta-
bility of three-dimensional January and July flows.
J.
Atmos.
Sci.
40,836-855.
Frederiksen, J. S.
(1983b).
A unified three-dimensional instability theory of the onset ofblock-
ing and cyclogenesis.
11.
Teleconnection patterns.
J.
Atmos.
Sci.
40,2593-2609.
Frederiksen. J.
S.
(1984).
The onset
of
blocking and cyclogenesis in Southern Hemisphere
synoptic flows: Linear theory.
J.
Atmos.
Sci.
41,
1
1
16
-
1
13
1.
Frederiksen,
J.
S.
(1985).
The geographical locations of Southern Hemisphere storm tracks:
Lineartheory.
J.
Atmos.
Sci.
42,710-723.
Frederiksen, J.
S.,
and Pun,
K.
(1985).
Nonlinear instability and error growth in Northern
Hemisphere three-dimensional
flows:
Cyclogenesis, onset-of-blocking and mature anoma-
lies.
J.
Atmos.
Sci.
42, 1374- 1397.
Frederiksen, J.
S.,
and Sawford,
B.
L.
(1980).
Statistical dynamics oftwodimensional inviscid
flow on a sphere.
J.
Atmos.
Sci.
37,7 17
-
732.
Gall, R.
(1976).
A
comparison
of
linear baroclinic instability theory with the eddy statistics of a
general circulation model.
J.
Afmos.
Sci.
33,
349-373.
Gamott,
E.
B.
(1
904).
Long range forecasts.
U.S.
Weather
Bur.
Bull.
35.
Green, J.
S.
A.
(1977).
The weather during July,
1976:
Some dynamical considerations on the
drought.
Weather
32,
120- 126.
Hansen,
A.
P.,
and Chen,
T.
C.
(1982).
A spectral energetics study of atmospheric blocking.
Mnn. Weather Rev.
110, 1146-1
165.
Illari,
L., and Marshall,
J.
C.
(1983).
On the interpretation
of
eddy fluxes during
a
blocking
episode.
J.
Aimos.
Sci.
40,2232-2242.
Ji,
L.
R.,
and Tibaldi,
S.
(1983).
Numerical simulation of a
case
of blocking: The effects of
orography and land-sea contrast.
Mon.
Weuther
Rev.
111,2068-2086.
Lau,
N.
(
198
1
).
A
diagnostic study
of
recurrent meteorological anomalies appearing in a
1
5-year
simulation with a GFDL general circulation model.
Man.
Weather Rev.
109,2287-231
I.
Lejenk, H.
(1977).
On the breakdown
of
the westerlies.
Atmosphere
15,89-
1
13.
Lejem,
H.
(1984).
Characteristics
of
Southern Hemisphere blocking
as
determined from a
time
series
of observational
data.
Q.J.R.
Meteorol.
Soc.
110,967-979.
Lorenz,
E.
N.
(1960).
Energy and numerical weather prediction.
Tellus
12, 364-373.
Namias, J.
(1947).
Characteristics of the general circulation over the northern hemisphere
Namias, J.
(1950).
The index cycle and
its
role in the general circulation.
J.
Meteorol.
7,
OConnor,
J.
(1963).
The weather and circulation of January
1963.
Mon.
Weather
Rev.
91,
Rex, D.
(
1950).
Blocking action in the middle troposphere and
its
effect upon regional climate.
Rossby,
C.
G.
(1950).
On the dynamics
of
certain types
of
blocking waves.
J.
Chin. Geophys.
Shutts,
G.
J.
(
1983).
The propagation
of
eddies in diffluent jetstreams: Eddy vorticity forcingof
‘blocking’ flow fields.
Q.J.R.
Mereorol.
Soc.
109,
737-761.
Simmons,
A.
J., and Hoskins,
B.
J.
(1978).
Thelifecyclesofsomenonlinearbaroclinic
waves.
J.
Atmos.
Sci.
35,414-432.
Simmons,
A.
J., Wallace, J. M., and Branstator,G. W.
(
1983).
Barotropic wave propagation and
instability, and atmospheric teleconnection patterns.
J.
Atmos.
Sci.
40,
1363- 1392.
Thompson,
P.
D.
(1957).
A
heuristic theory of large-scale turbulence and long period velocity
variations in barotropic flow.
Tellus
9.69-
9
1.
Trenberth, K.
E.
(1976).
Spatial and temporal variations of the Southern Oscillation.
Q.J.R.
Meteorol.
SOC.
102,639-653.
during the abnormal winter
1946-1947.
Mon. Weather
Rev.
75, 145- 152.
130- 139.
209- 2
1
8.
Tellus
2, 196-21
1.
SOC.
2,
1
-
13.
INSTABILITY THEORY AND NONLINEAR EVOLUTION
303
Trenberth,
K.
E., and Paolino,
D.
A.
(198
1).
Characteristic patterns
of
variability of sea level
Troup,
A.
J.
(1965).
The Southern Oscillation.
Q.J.R. Meteorol.
SOC.
91,490-506.
Tucker,
G.
B.
(1979).
Transient synoptic systems as mechanisms
for
the meridional transport:
An observational study in the Southern Hemisphere.
Q.J.R. Meteorol.
SOC.
105,657-672.
van Loon, H., and Madden, R.
A.
(1981).
The Southern Oscillaton. Part
I:
Global associations
with pressure and temperature in the northern winter.
Mon.
Weather Rev.
109,
1150-
1
162.
van Loon, H., and Rogers, J. C.
(1
978).
The seesaw in winter temperatures between Greenland
and Northern
Europe.
Part
I:
General description.
Mon.
Weather Rev.
106,296-3
10.
van
Loon,
H.,
and Rogers,
J.
C.
(198
I).
The Southern Oscillation, Part
11:
Associations with
changes in the middle troposphere in the northern winter.
Mon.
Weafher Rev.
109,1163
-
1168.
pressure in the Northern Hemisphere.
Mon.
Weather Rev.
109,
1
169-
1
189.
Walker, G. T., and Bliss, E. W.
(1932).
World weather.
Mem. R. Meteorol.
SOC.
4,
53-84.
Wallace, J.
M.,
and Gutzler,
D.
S.
(1981).
Teleconnections in the geopotential height field
during
the Northern Hemisphere winter.
Mon.
Weather Rev.
109, 784-812.
Yeh,
T.
C.
(
1949).
On energy dispersion in the atmosphere.
J.
Meteorol.
6,
1
-
16.
Youngblutt, C.
E.,
and Sasamori, T.
(1
980).
The nonlinear effects
of
transient and stationary
eddies on the winter mean circulation. Part
I:
The diagnostic analysis.
J.
Atrnos.
Sci.
37,
1944- 1957.