Download MEAN TEMPERATURE AND WIND FIELDS

MEAN TEMPERATURE AND WIND FIELDS ALONG
80 DEGREES WEST
by
J.M.H. Tissot van Patot
A thesis submitted to the Faculty
of Graduate Studies and Research in
partial fulfilment of the requirements
for the degree of Master of Science.
Department of Meteorology,
McGill University,
Montreal.
January 1963
ii
PREFACE
This thesis is presented in partial fulfilment of
the requirements for the Master of Science degree in
Meteorology
at McGill University.
The study was made possible by the Meteorological
Branch of the Department of Transport which allowed the
author to attend McGill University for post-graduate
study and research. The research was conducted under
the direction and with the assistance of Dr. Byron
w.
Boville, who gave invaluable help and constructive critioism.
The author wishes to extend particular thanks to Miss Mona
McFarlane, who guided the programming part to a succesful
end. The author is grateful to Mr. André Castonguay
who helped to design the grid and the abstracting
procedures; to the following for assistance in data
abstraction and card punching: Mrs. Jane Hazelzet and
Mrs. Joy Bird, Messrs. Samuel Li, Stephen Francis,
Eric Visser, Richard Shorrock, John Evans and David
Elcombe; to Professer W.D. Thorpe, Mrs. Barbara Fox,
Mrs. Ulla-Brita Manley and Miss Joan McPherson who
discussed particular programming problems which arose
during the course of this study; to Mrs. Anna Kruczkowska
who prepared the final cross-sections; to his fellow
students Messrs. Amos Eddy, Graeme Morrissey, Marvin
iii
Olson and Brian O'Reilly for their valuable discussions;
and to my wife who prepared the typescript.
iv
TABLE OF CONTENTS
Page
Preface
ii
List of Appendices
Abstract
vi
vii
1•
Introduction
1
2.
Data Analysis and Processing
3
2.1
Analysis
3
2.2
Processing
4
3.
Computation of Means
7
3.1
Geographical Means
7
3.2
Means Oentred on Other Parameters
7
4.
Analysis of Resulta
10
4.1
Format
10
4.2
Geographical Mean Cross-Sections
10
4.3
Origin at the Polar-Front Jet Stream
14
4.4
Origin at the Maritime Jet Stream
16
4.5
Origin at the Arctic Jet Stream
17
4.6
Origin at the Polar-Night Jet Stream
18
4.7
Origin at the -130 Isotherm at 500 mb
19
4.8
Origin at the -220 Isotherm at 500 mb
20
4.9
Origin at the -310 Isotherm at 500 mb
22
4.10
Origin at the -600 Isotherm at 50mb
23
4.11
Composite Cross-Sections
23
5.
Conclusions
25
v
Table of Contents (continued)
Page
References
27
Appendices
28
vi
LIST OF APPENDICES
Appendix A (figures A-1 to A-40)
Page
Mean seasonal cross-sections showing
isotherme and isotachs with their standard
deviations for the period June 1959 - May
28
1960.
Appendix B (tables B-1 to B-4)
Tables of means and standard deviations
of jet stream core positions and speeds
and isotherm positions by months and
season~
42
Appendix C
List of upper air stations along
80 degrees west supplying the basic
data for the cross-sections.
48
vii
ABSTRACT
Mean seasonal cross-sections along 80 degrees west
were constructed from daily analysed data. By this
procedure it was possible to formulate means and
standard deviations with respect to various jet stream
cores and selected temperatures as well as the usual
geographical means. A set of auch sections for the
period June 1959 - May 1960 is presented and discussed.
1•
1.
INTRODUCTION
The mean state of the atmosphere bas been represented
horizontally by mean sea level and upper air maps, and
vertically by mean cross-sections. Most of the averaging
processes tend to smooth out the important shifting
features of the atmosphere and mean cross-sections
show jet streams as broad smeared-out wind maxima.
The object of this study was to overcome this
deficiency through the construction of mean cross-sections
with reference to some characteristic features of the
wind and temperature fields. The availability of analysed
daily cross-sections along 80 degrees west made such
a study possible.
A large number of mean cross-sections have been
published for various meridians. The first major study
was carried out by Hess (1948) along the 80 west meridian
for the period 1942-1945. In his approach Hess used
mean radiosondes and upper air maps thus limiting
himself to the use of geographical coordinates. Kochanski
(1955) elaborated on this study and extended it to 10mb,
also using mean radiosondes and maps as basic material.
An entirely different approach was taken by Mcintyre
and Lee (1954). Instead of taking geographical coordinates
for a reference frame, as Hess and Kochanski did, they
2.
constructed the means with respect to some of the moving
features of the weather map.
In this study these two approaches have been
combined with machine methods to obtain a set of mean
cross-sections with reference to characteristic
features as well as the usual geographical coordinates.
2.
DATA ANALYSIS AND PROCESSING
2.1
Analysis
Most of the basic data used on the cross-sections
were taken directly from the teletype circuits at the
Central Analysis Office of the Meteorological Branch,
Department of Transport, at Montreal International
Airport. Values of temperature and wind were plotted
for all the reported points above 500 mb. Below 500 mb
the values were usually plotted only at the standard
levels, 1000, 850 and 700 mb. The analyses will thus
be least representative near the ground. The reporting
stations which were plotted, are listed in Appendix
c.
Supplementary data were added later to clarify the
analyses in critical areas. These were taken from the
Daily Series, Northern Hemisphere Data Tabulations Part II,
United States Weather Bureau (1959-1960).
A standard form of cross-section was used extending
from the Canal Zone to the North Pole. The ecale of the
horizontal is 1 : 20 million, which is the same ecale
as the upper level maps used for eupporting material.
The map projection is polar stereographie true at
60 degrees north. The vertical ecale extending to
10mb is a logarithmic pressure scale. To limit the
aize of the cross-section the ecale is reduced by
25 percent above 500 mb. The same cross-section was
again used for the final resulta.
The cross-sections were analysed on a daily basie
by staff members of the Department ot Meteorology of
McGill University. In the original analyses little
allowance could be made for incorrect data, but
appropriate upper level maps were used as a guide
to bridge the gaps left by incomplete data. The temperature
field was analysed directly. The wind analyses were
restricted to the zonal component, i.e., the wind
component perpendicular to the cross-sections, to
permit thermal consistency. All analyses were re-examined
and extended to 10 mb. Completely missing radiosondes
were added and ascents which appeared to be in error
were checked against the published United States Weather
Bureau values (op. cit.).
2.2
Processing
The data were extracted from each daily section
for an 806 point grid. This grid contained 26 columns
of 31 points. The horizontal spacing is equal to the
grid spacing used for the numerical weather analysis
and prediction experimente by the Department of Meteorology
of McGill University, i.e., 381 km. The vertical
spacing is 1 km and is based on the "ARDC model atmosphere",
for which data were taken from the Handbook of Geophysics
{1960).
Values of zonal wind and temperature were required
at grid points. A dense grid was chosen to obtain a
good representation of the wind field near jet streams
and of the temperature field in the baroclinic zones.
But outside these areas where the wind and temperature
fields varied slowly auch a high density was unnecessary.
To shorten the very time-consuming data extraction
values of these fields were only taken at characteristic
points, the intermediate values being left for machine
interpolation.
These data were punched into cards, together with
information concerning the length of intervals between the
characteristic points and an identifying number. The
special information required for the identification
of the date, the position of jet streams and certain
isotherme was abstracted at the same time and punched
into cards.
The McGill University computer, IBM model 1410,
was programmed to carry out the interpolation between
the characteristic points in the following manner.
The first card read contained the date and special
information. Each of the following cards contained the
abstracted data for one column, plus the way these data
6.
were distributed. Each column was expanded to its normal
aize and the missing values were interpolated. After
completing the twenty-six columns the entire array
was checked for internal consistency and a list of
errors and suspect values was printed. The entire array
was then printed in a format almost identical to the format
of the original grid. Finally the array plus the identifying
information were transferred to magnetic tape. The
whole procedure was repeated for each day. The errors and
the doubtful values were checked and corrected and the
corrections were inserted in the original record as
well as in the magnetic tape. After this processing
was completed the wind and temperature values for almost
300,000 grid points were stored on magnetic tape in array
form ready for the computation of the means and standard
deviations.
7.
3.
COMPUTATION OF MEANS
3.1
Geographical Means
The computation of the means and standard deviations
with respect to geographical coordinates was done in a
standard way for each grid point. Means and standard
deviations were computed for each month and for each
season. The seasons were defined in the usual climatological
sense, i.e., three-month periode starting at June 1st,
September 1at, December 1st and March 1st (Huschke (1959)).
These and all following computations were performed
at the Institute of Computer Science of the University
of Toronto using the IBM model 7090 computer.
3.2
Means Centred on Other Parameters
An inspection of the daily cross-sections revealed
that two tropospheric jet streams occur regularly.
Frequently there were even three jet streams. They can
be grouped together into three different classes with limita
at 225 and 300 mb. The jet streams appear to be associated
with particular 500 mb temperatures. The following
500 mb isotherme are the most favoured: -130, -22C
and -31C. During the colder half of the year a jet stream
appears frequently at high levels. It is generally
centred at or above 10 mb, but its geographical position
8.
is similar to the position of the wind maximum at 25 mb.
This jet stream appears to be closely associated with the
-600 isotherm at 50 mb. In this context a jet stream
was defined as a zonal wind maximum of at least 30 mps.
The nomenclature originated by Anderson, Beville and
McClellan (1955) is here applied to the three tropospheric
jet streams. The southernmost jet stream, which occurs
above 225 mb will be referred to as the polar-front jet
stream. The jet stream which occurs between 225 and 300 mb
will be called maritime jet stream and the northernmost
one, occurring below 300 mb will be called arctic jet
stream. The stratospheric jet stream will be referred
to as the polar-night jet stream after Kochanski (1955).
The jet streams were identified, for computing
purposes, by the column number nearest to the core.
A similar procedure was followed for the isotherms.
When computing the means and standard deviations
with respect to these fluctuating origins, it was
necessary to create a master array. This master array
had a central reference vertical and 52 columns, or
twice the widtb of the 26-column individual arrays.
After shifting the individual origine to the central
vertical the daily arraye were added into this master
array. Subsequent computations were performed on the
master array, keeping account of the number of additions
9.
into each column.
Due to the shifting origin not every column in
the master array had the same number of columns added
into it and a selection process was required. In order
to use the original print routine which provides output
crosA-sections on the appropriate scale the following
editing procedure was used. Twenty-six columns were
printed from the master array starting with the first
column containing at least two-thirds of the total number
of additions. This did not provide an equivalent eut-off
at the northern end of the array, however a check
showed that in most cases only the last few columns
would have been affected. This procedure yielded eight
sets of mean cross-sections using either one of the
four jet streams or one of the four isotherme as origin.
Each set consists of twelve monthly and four seasonal
means.
10.
4.
ANALYSIS OF RESULTS
4.1
Format
For better visual convenience the resultant mean
cross-sections have been grouped together in Appendix A.
Similarly tables of means and standard deviations of the
jet stream and isotherm positions and jet stream core
speeds, are to be found in Appendix B. The description
and discussion consider the cross-sections in three
main groups; first those with respect to geographical
coordinates, second those with a jet stream as origin
and third those with an isotherm-isobar intersection
as origin. On the cross-sections in the last two groups
two latitudes are indicated. These give a horizontal
frame of reference and actually represent horizontal
distances from the mean position of the origin.
4.2
Geographioal Mean Cross-Sections
The mean summer cross-section (fig. A-1) is
charaoterized by a weak west wind maximum near
50 degrees north, overlying the zone of greatest
temperature gradient. The highest wind speed of
26 mps oocurs slightly above 200 mb and the southward
extension of the maximum continues at about the same
level. This is significantly lower than the tropical
11 •
tropopause at about 80 mb. This phenomenon occurs on
all cross-sections and indicates that important
stratospheric-tropospheric mixing takes place at this
longitude.
There are two well-defined easterly wind systems
in southerly latitudes. The low-level trades reach a
maximum near 3 km. Going upwards the winds decrease to
a minimum near 10 km and then increase again to a
stratospheric maximum of 18 mps at 25 km. This maximum
occurs near 25 degrees north. Polar easterlies occur
north of 80 degrees, but remain very weak.
The oscillations of the main baroclinic zone between
40 and 70 degrees north are shown by the high standard
deviations of temperature (fig. A-2). The relative
minimum above this zone coincides with the level of
maximum wind which confirma the mean thermal wind balance.
The standard deviation of wind similarly has high
values just below the general tropopause level. The
existence of two centres, one near the jet stream core
and one near 35 degrees north is associated with the
occasional excursions of a jet stream to low latitudes.
The fall cross-section (fig. A-3) shows much the
same pattern. The jet stream has intensified to about
33 mps, and moved to about 45 degrees north. Its southward
extension has now penetrated to about 15 degrees north.
12.
Tbe subtropical easterlies as well as the polar easterlies
have decreased in intensity as well as in extent. A new
feature is a wind maximum at 60 degrees north at 10 mb.
In the temperature field a general cooling is evident
partioularly north of 30 degrees. In comparison with
the summer the most notable feature is the reversal of
the temperature gradient at very high levels. A cooling
of about 25 degrees bas taken place at 25 km. The
temperature maximum indicating the warm band north of
and above the jet stream level is very well marked. The
variability of the wind field (see fig. A-4) has not
ohanged signifioantly. The jet streams range from about
65 degrees north to 30 degrees north. The wind maximum
at high levels is not too constant. The restlessness
of the major baroclinio zone is the prominent feature in
.
the variability of the temperature field. The only other
feature worth noting is the large variability near the
Pole at very high levels, indicative of the increasing
polar-night and a gradual oooling.
The southward trend whioh started in the fall bas
been oontinued into the winter (fig. A-5). The jet
stream bas intensified to nearly 50 mps and is now
oentred near 35 degrees north. A secondary wind maximum
also exists at 68 degrees north. This maximum not only
shows up in the mean, but also in the standard
13.
deviation. It indicates that the arctic jet stream
does occur as a separate entity. The sub-tropical as well
as the polar easterlies have all but disappeared. The
high level wind maximum bas become very broad and indefinite.
The temperature field bas undergone more cooling but
the general appearance is much as it was during the fall.
The warm belt in the lower stratosphere is again one of
the significant features. In the standard deviations
of the wind field (fig. A-6) the
~ost
noteworthy features
are the small maximum near 68 degrees north which was
mentioned before, and the broad maximum between 35 and
55 degrees north. The southernmost maximum bas disappeared
although the 10 mps isopleth suggests a slight maximum
between 20 and 30 degrees north. The standard deviation
of the temperature field does not show nearly as much
variation in the troposphere as in the fall, but otherwise
the pattern is very similar. The marked minimum at the
level of maximum wind is still in evidence.
Turning to the spr.ing months (fig. A-7) the most
apparent changes are the continued southward motion of
the jet stream, its very broad northward extension and
the disappearance of the high level wind maximum. The
polar easterlies and the subtropical tropospheric easterlies
have reappeared. As far as the temperature field is
concerned the most significant change is the warming
14.
of the lower and middle stratosphere in high latitudes,
The standard deviation of the wind field (fig. A-8)
has a pattern similar to the one in the summer and fall
except for the very high variability associated with the
disappearance of the polar-night wind maximum. Similarly
the standard deviation of the temperature field reflects
the rapid stratospheric warming, which occurred at the
end of March (An Atlas of Stratospheric Circulation
(1962)), In the lower stratosphere and in the troposphere
the patterns show relatively little change.
4.3
Origin at the Polar-Front Jet Stream
The cross-sections with the polar-front jet stream
as origin are to be found in figures A-9, A-10, A-11
and A-12, and the corresponding table of position in
Appendix B-1.
It is evident from the table that this jet stream
reaches its most northerly position late in the summer,
i.e., August (46 degrees north). Its southward motion
is very slow and gradual and the southernmost position
is reached in the spring. The jet stream attains its
greatest intensity before reaching its most southerly
position and has a mean zonal wind component of 65 mps
in February. The lowest intensity is found in July
when the maximum value is 39 mps. It appears that the
15.
polar-front jet stream, at least in the period from
October to March, is closely associated with the
-130 isotherm at 500 mb.
The summer cross-section (fig. A-9) shows the
polar-front jet stream in its relation to the temperature
field. The jet stream is associated with a strong
baroclinic zone. It has a very marked extension northward
indicating that frequently more than one jet stream
occurs at a time. This northward extension lies at the
temperature minimum. Going southward from the jet stream
the level of maximum wind is not too sharply defined,
but it is well below the tropopause level. Continuing
to the fall season (fig. A-10) the appearance changes
very little. Some southward motion and intensification
of the jet stream occurs.
The winter season (fig. A-11) shows the most intense
jet stream with lateral extensions both to the north
and to the south. The northward extension signifies the
occurrence of multiple jetstream cores. It occurs at
the tropopause level. There is even a weak maximum
of 10 mps at 66 degrees north. The southward extension
lies between 150 and 200 mb, well below the tropical
tropopause which occurs at about 80 mb.
The pattern of the spring cross-section (fig. A-12)
shows a continued southward motion of the jet stream,
16.
but the northward extension indicates frequent excursions
of the other jet streams into northern latitudes.
4.4
Origin at the Maritime Jet Stream
The cross-sections with the maritime jet stream
as origin are to be found in figures A-13, A-14, A-15
and A-16, and the corresponding table of positions in
Appendix B-2.
This jet stream is the strongest jet stream crossing
80 degrees west. Its zonal wind speed varies from a
low of 40 mps in August to a high of 67 mps in January.
As is the case with the polar-front jet stream it ranges
through about 18 degrees of latitude during the year,
reaching its northernmost position in August (57 degrees
north) and its southernmost position in March (39 degrees
north). The correlation with the -220 isotherm at 500mb
holds very well in the period October to April.
The summer cross-section (fig. A-13) shows a
classical jet stream picture. On the northern side
of the jet stream the wind shear is strong, amounting
to about 3.4 kt per degree of latitude (3 x 10-5 sec- 1 ).
On the southern aide the wind shear is much less and
the very noticeable level of maximum wind around 200 mb
is well below the tropopause. The fall cross-section
(fig. A-14) shows the slow intensification and the
17.
beginning of the southward motion of the jet stream
from its summer position.
The winter mean (fig. A-15) shows the most intense
pattern. The wind shear in the northern side has now
increased to 4.4 kt per degree of latitude (4 x 10-5 sec- 1 ).
There is an upward shift of the jet stream. This is
due to the fact that very often in winter a
double
structure occurs in combination with the polar front
jet stream. The pattern on the spring mean (fig. A-16)
indicates a decrease in intensity and a northward retreat
of the jet stream.
4.5
Origin at the Arctic Jet Stream
The cross-sections with the arctic jet stream as
origin are to be found in figures A-17, A-18, A-19 and
A-20, and the corresponding table of positions in
Appendix B-3.
It is obvious from the table that the number of
occasions with an arctic jet stream in the summer months
is very small; four, one and two respectively for June,
July and August. From September on the number of occasions
increases to a maximum of 25 in January and decreases
afterwards. The maximum zonal winds, exclusive of the
summer months, ranges around 40 mps. The arctic jet stream
is never a major jet stream, but from the latitudinal
18.
separation which exista between the maritime jet stream
and this one it is evident that the arctic jet stream is
a separate entity. Although the relation is not as close
as with the other two jet streams, it is felt that the
-31C isotherm at 500 mb is a fair criterion for positioning
this jet stream.
The summer cross-section (fig. A-17) shows a very
erratic pattern which is mainly due to the small sample (7).
The three other seasons (fig. A-18, A-19, A-20) show a
more definite pattern with the arctic jet stream near
60 degrees north and a second maximum approximately
30 degrees farther south. Particularly in the fall and
winter there is an apparent linkage between this
tropospheric jet stream and the polar-night jet stream.
4.6
Origin at the Polar-Night Jet Stream
The cross-sections with the polar-night jet stream
as origin are to be found in figures A-21, A-22 and
A-23, and the corresponding table of positions in
Appendix B-4.
On the geographical mean cross-sections the
polar-night jet stream was evident only as a
diffuse wind maximum in the middle stratosphere.
From the accompanying standard deviations it was
obvious that it was an active system. Using this
19.
jet stream as origin a better representation can
now be made.
The polar-night jet stream occurs 6 or 7 months of
the year and even then it does not cross 80 degrees west
daily. In 1959-1960 this jet stream did not occur until
October, and throughout October and November occurrences
remained rather eparse. During the period December to
March the jet stream occurred only on about 6 out of
10 days. Its average maximum speed is in the order of
40 mps. Its monthly mean positions are quite fluctuating,
but it appears to have its most southerly position in
January. There exists a fair correlation between the
-60C isotherm at 50 mb and the polar-night jet stream.
The three cross-sections show a high degree of
similarity. Although there is a linkage between the
tropospheric and the stratospheric wind systems, the
core of the polar-night jet stream occurs further north
and at or above 10 mb. In the spring however the linkage
becomes rather weak with the tropospheric systems occurring
30 to 35 degrees away from the polar-night jet stream.
4.7
Origin at the -130 Isotherm at 500mb
The cross-sections with the -13C isotherm at
500 mb as origin are to be found in figures A-24, A-25,
A-26 and A-27, and the corresponding table of positions
20.
in Appendix B-1.
The mean monthly latitude of this isotherm varies
about 22 degrees of latitude throughout the year, from
50 degrees north in August to 28 degrees north in March.
The correlation between the isotherm and the polar-front
jet stream is very good in the period October to March.
The summer mean (fig. A-24) shows a jet stream
coincident with the isotherm position. This jet stream
is the resultant of overlapping parts of the polar-front
and the maritime jet streams. It has a maximum of a little
more than 30 mps. The fall (fig. A-25) shows the same
pattern. The core speed of the jet stream has now increased
to nearly 40 mps. The rather weak wind shear on
the north aide of the jet stream indicates that it
is still a mean of overlapping parts of the two main
jet streams. Going into the winter (fig. A-26) the pattern
intensifies markedly, but retains its general appearance.
The highlight of the spring mean (fig. A-27) is the
north-south elongation of the jet stream. This is due to
the fact that now the polar-front and the maritime jet
streams are farthest apart.
4.8
Origin at the -220 Isotherm at 500 mb
The cross-sections with the -220 isotherm at
500 mb as origin are to be found in figures A-28, A-29
21.
A-30 and A-31, and the corresponding table of positions
in Appendix B-2.
The isotherm intersection moves southward from
69 degrees north in July,to 37 degrees north in March.
It will be noted that the correlation between the isotherm
and the maritime jet stream is very good from October
to April.
In the summer (fig. A-28) the jet stream is evident
about 10 degrees further south than the isotherm position.
It is just south of the major baroclinic zone. The jet
stream bas a well defined extension southward below the
tropopause. The fall (fig. A-29) shows a general
intensification of this pattern. The isotherm position
now indicates the position of the baroclinic zone and
is only a little north of the jet stream. The winter
(fig. A-30) shows the most intense system with the wind
maximum in the jet stream core going up to almost 50 mps.
The discrepancy between this and the tabulated value
of 59 mps is due to the fact that the -22C isotherm
occurred on all days, whereas the jet stream did not
always meet the criterion set for it. The jet stream
does tend to remain smeared out. Going into the spring
season (fig. A-31) a decrease in intensity and a northward
shift will be noted.
22.
4.9
Origin at the -310 Isotberm at 500 mb
The cross-sections with the -310 isotherm at
500 mb as origin are to be found in figures A-32, A-33,
A-34 and A-35, and the corresponding table of positions
in Appendix B-3.
The -310 isotherm is not very often present at
500 mb in the summer. It did not occur in July and only
twice in August. However its appearance became more and
more frequent during September and it was present
continuously from late September to the middle of May.
Its furthest southward extension occurred in March.
The summer cross-section (fig. A-32) shows the mean
position of the isotherm as the centre of a cold vortex
near 67 degrees north. The wind field shows a broad belt
of westerlies south of the vortex and an easterly stream
to the north of it. Going from summer into fall (fig. A-33)
there is a consolidation of the pattern with a single
jet stream about 10 degrees further south than the
isotherm. In the winter (fig. A-34) this distance
decreases to nearly 5 degrees, but now the maximum
associated with the isotherm becomes indistinct. Another
much stronger but broader maximum appears 20 to 25 degrees
further south. This is the reflection of the other two
tropospheric jet streams. The spring sections (fig. A-35)
still shows this pattern but now the arctic jet stream is
23.
again more a definite entity.
4.10 Origin at the -600 Isotherm at 50mb
The cross-sections with the -600 isotherm at 50 mb
as origin are to be found in figures A-36, A-37 and A-38,
and the corresponding table of positions in Appendix B-4.
The -600 isotherm did not appear until October and
from then until the end of March it appeared only on
about two out of every three days. Its latitude followed
the same trend as the latitude of the polar-night jet
stream. Although the isotherm latitude remains the same
throughout the three seasons the jet stream positions
fluctuate. They still are very near the mean positions
which are listed in table B-4. The linkage between
the stratospheric and the tropospheric wind systems
does not appear to be very strong.
4.11 Composite Cross-Sections
Figures A-39 and A-40 show two composite crosssections for the winter season. On both sections only
the wind field is depicted.
Figure A-39 is a èomposite of the four means where
the jet stream cores were used as origin. From each of
these four only the relevant parts were taken. This section
illustrates very well the relative position of the jet
24.
streams, both horizontally as well as vertically. The
most notable features are: the southward extension of the
polar-front jet stream just above the 200 mb level, but
well below the tropical tropopause; the large horizontal
separation between the maritime jet stream and the
arctic jet stream, amounting to about 20 degrees of
latitude; and the apparently well-defined linkage between
the arctic jet stream and the polar-night jet stream.
Figure A-40 is constructed similar to the previous
one, but the cross-sections used were the ones which
had the various isotherme as origin. Here the picture
changes and it shows the intimate relationship of the
polar-front jet stream and the maritime jet stream.
These two jet streams now all but coincide. The arctic
jet stream again stands apart as a separate entity, but the
linkage with the polar-night jet stream is not as striking
as on the previous section.
25.
5.
CONCLUSIONS
The results show that the three tropospheric
jet streams exist as separate and distinct entities.
Both the polar-front jet stream and the maritime
jet stream occur throughout the year, but the arctic
jet stream is mainly a phenomenon of the three colder
seasons.
The close relationship which existed particularly
in winter between the various jet streams and the selected
upper air temperatures, illustrates the significance
of the main frontal zones for climatological and synoptic
purposes. The relationship during the summer months
might be improved by allowing for the shift of the
jet streams to higher temperatures.
Although the polar-front jet stream and the maritime
jet stream are separate entities, they often occur close
together as a double cored structure. This effect is
not completely eliminated in the selective averaging
process and some distortion remains in their respective
means.
Another notable feature is the level of maximum
wind south of the polar-front jet stream at the 200 mb
level. The !act that this occurs well below the tropical
tropopause indicates that significant stratospheric-
26.
tropospheric mixing takes place here.
During the period under consideration the polarnight jet stream was not too well-defined on the mean
geographical cross-sections. However the high standard
deviations at the upper levels indicate an active
system with large variability.
On the specialized cross-sections the polar-night
jet stream shows up quite clearly and is closely
associated with the -60C isotherm at 50 mb. On these
sections it is also evident that the cold pool with
temperatures from -?OC to -SOC occurs to the north of
the jet stream. As a result of the large meridional
motions this cold pool is smoothed considerably on the
geographical means. The resulte suggest that there is
some linkage between the stratospheric system and the
tropospheric jet streams, at least in a geographical
sense.
In conclusion it is shown that machine processing
methode can not only be used to get an accurate
climatological representation of various parameters,
but can at the same time be used to highlight certain
characteristic features of the fields under consideration.
27.
REFERENCES
An
Atlas of Stratospheric Circulation April 1959 May 1960, 1962, Defence Research Board of Canada,
D.Phys.R.(G) Mise
G10 (Arctic Meteor. Res. Gp.,
Pub. in Meteor. No 49)
Anderson, R.,
B.W. Boville and D.E. McClellan, 1955:
"An operational frontal contour analysis model",
Quart. J. R. Meteor. Soc., 81, pp. 588-599.
Daily Series, Synoptic Weather Maps, Part II, Northern
Hemisphere Data Tabulations, Daily Bulletin,
United States Weather Bureau.
Handbook of Geophysics, revised edition, 1960, Macmillan
Company, New York, N.Y.
Hess, s.L., 1948: "Some new mean meridional cross
sections through the atmosphere", J. Meteor., 5,
pp. 293-300.
Huschke, R.E., 1959: "Glossary of Meteorology",
American Meteorological Society, Boston, Mass.
Kochanski, A., 1955: "Cross sections of the mean zonal
flow and temperature along 80° W", J. Meteor., 12,
pp. 95-106.
Mcintyre, D.P. and R. Lee, 1954: "Jet streams in middle
and high latitudes", Proc. Toronto Meteor. Conf. 1953,
pp. 172-181, Royal Meteorological Society, London.
28.
APPENDIX A
Mean Seasonal Cross-Sections
The cross-sections are analysed for temperature
in degrees Celcius and zonal wind in meters per second,
winds from the west are positive and from the east negative.
The isotherme are drawn at 10 degree intervals and the
isotachs at 10 mps intervals. When necessary to clarify
patterns half-intervals are used. On the sections giving
the standard deviations (fig. A-2, A-4, A-6 and A-8)
the intervals are 2 degrees for the temperature and
5 mps for the zonal wind.
The daily cross-sections were averaged with regard
to their standard geographical position to derive the
seasonal mean geographical cross-sections. The standard
deviations of these means were obtained at the same time.
On each daily section the latitude of the polar-front
jet stream core was identified, tabulated and averaged
(table B-1). Then using a machine program each array
representing a daily section was shifted laterally
such that its jet stream position coincided with the
mean position. The time-averaging process was finally
carried out to yield a mean seasonal cross-section with
the origin at the polar-front jet stream. A similar
procedure was followed for the other characteristic origine.
29.
/
- - - ____.; -.JO----
~--------::~
/
60
200
-50
40
30
0
/·~00
-10
.
' ·'
1
\
\
\
\
\
0
" 10
1
-5
1000
'
1
"'
i
20
- - - isotherms (°C)
S.D. of t emperature
Fig. A-1 and A-2
- - - isotachs (mps)
-- S.D. of zonal wind
30.
r--------
0 \"""--..j__
\
-------10--\~~--
Fig. A-3 and A-4
31 •
/
--.....
./
'""" ·-
18 . /
---55----....... ,
\
+
so•N
0
2
/
/- - -.
"""
(
Fig. A-5 and A-6
i
!
\
/
/
32.
\
\
\
\
\
\
"""'"'
Fig. A-7 and A-8
33.
/
/~------../
1
--
i //
./
~o---_
'"
1\
1
~
~
--
"-
~-
1
1
--+"'
1
1
1
1
1
'" '\
0
""\
~
~
~
1
!'"'\
\
~
1
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!12
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§
~
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1 l
1
11
1 \
1
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~~
/1
1
1
1
'<.
1
"'j/)
1
1
1
1
/(
/+ "
1
r
l//
·-... ·-....
1
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1
Fig. A-9, A-10, A-11 and A-12
/
l '
(
1
1
/''
/
1
/
+g
34.
35.
Fig. A-17, A-18, A-19 and A-20
36.
__
------, , . . . .__
.......
l
1
1
1
1
1
1
Fig. A-21, A-22 and A-23
\
37.
_/
\
1
/
\
\
\
\
."'m
"\
\
\ li
~
\ ,
;2
"g
'"
~?r?~?
0
Q
2
\
\
j
\
'-
;
z
ii!
j
\
\
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1
1
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~
Fig. A-24, A-25, A-26 and A-27
~
§
38.
1
1
\,/"
---- ----
,.""-._
~,
"\
\
1
1
1
1
Fig. A-28, A-29, A-30 and A-31
39.
/
,.-
1
1
1
1
1
1
1
/
~
/'
Fig. A-32, A-33, A-34
and
A-35
40.
Fig. A-36, A-37 and A-38
41 •
Mb.
C
Krn
10
i
\
\
\
i
i
i
0
\
\
\
i
\
\
i
1
1
i
i
/ 1 i
i
/ 1i
1
1
\
\
\
,/
1
1
40
\
\
/_
i
i ii
i
\
\
1
----
1
'-30 '
/
1
/
1
---~
......
'\.
'\
/
\
\
~--
i
i
i
1
1
200
Mb
10
\
1
1
1
\
1
\
)
'
1
/
~0
'
~20./
;,/
"
J
-60
1
1
200
1
+
30
1
1
10
~00
Fig. A-39 and A-40
/
"
/'
/
1
42.
APPENDIX B
Tables of Means and Standard Deviations of Jet Stream
Core Positions and Speeds and Isotherm Positions by
Months and Seasons
The following four tables give the means and standard
deviations of the jet stream core positions and speeds
together with the same data for the appropriate isotherms.
The tables list both monthly and seasonal values.
Table B-1 gives these data for the polar-front jet
stream and the -130 isotherm at 500 mb. The number
of occurrences of the jet stream ranged between 15 and
31 per month with the exception of September when
it only occurred 9 times. The seasons had 49, 46, 85
and 80 occurrences respectively. The isotherm occurred
daily throughout the entire period.
Table B-2 gives the data for the maritime jet
stream and the -220 isotherm at 500 mb. The number of
occurrences of the jet stream ranged from 16 to 28 per
month and from 68 to 73 per season. The isotherm occurred
daily throughout the period except during July and August
when it existed only 22 and 28 times.
Table B-3 gives the data for the arctic jet stream
and the -310 isotherm at 500 mb. The number of occurrences
of the jet stream ranged from 1 to 25 per month and from
43.
7 to 48 per season. The isotherm made only 10 appearances
during the summer, but was a daily feature from late
September to late May.
Table B-4 gives the data for the polar-night jet
stream and the -600 isotherm at 50 mb. This jet stream
did not appear until October and even then the number of
occurrences were quite varied from month to month ranging
from 10 to 22. It disappeared again in April. Seasonally
it appeared
o,
15, 45 and 24 times. As far as the isotherm
is concerned the number of occurrences between October and
March varied from 17 to 29, with seasonal totals amounting
to
o, 46, 59
and 28.
44.
TABLE B-1
Mean and Standard Deviation of Monthly and Seasonal
Positions of the Polar-Front Jet Stream and the -13C
Isotherm at 500 mb with the Mean and Standard
Deviation of the Zonal Wind Speed of the Jet
Stream Core
Jet Stream
Latitude
Mean S.D.
Month
. Core S~e ed .
(mps
Mean S.D.
Isotherm
Latitude
Mean S.D.
June
Ju1y
August
September
Ootober
November
Deoember
January
February
Mar ch
April
May
1959
1959
1959
1959
1959
1959
1959
1960
1960
1960
1960
1960
36
44
46
43
41
36
32
31
32
29
29
29
5
5
5
7
6
5
4
5
4
4
7
4
44.2
39.0
39.8
42.8
53.0
47.9
50.9
58.9
65.3
58.6
42.4
45.6
8.5
6.0
7.4
10.2
8.1
9.7
8.2
8.1
7.8
14.4
10.6
9.7
47
49
50
47
40
35
30
31
31
28
33
36
8
5
4
6
4
4
5
Summer
Fall
Win ter
Spring
1959
1959
1959-60
1960
42
40
32
29
7
6
5
5
41.0
49.1
58.4
49.8
7.7
9.9
10.0
13.9
49
41
31
32
6
7
5
7
7
4
3
5
7
45.
TABLE B-2
Mean and Standard Deviation of Monthly and Seasonal
Positions of the Maritime Jet
Str~am
and the -22C
Isotherm at 500 mb with the Mean and Standard
Deviation of the Zonal Wind Speed of the Jet
Stream Core
Jet Stream
Latitude
Mean S.D.
Mon th
Core SJeed
(mps
Mean S.D.
Isotherm
Latitude
Mean s.n.
June
July
August
September
October
November
December
January
February
Mar ch
April
May
1959
1959
1959
1959
1959
1959
1959
1960
1960
1960
1960
1960
53
54
57
56
48
44
42
40
41
39
45
47
5
6
5
7
5
5
4
5
4
5
6
10
47.2
41.3
40.4
46.9
58.4
49.6
53.3
67.2
56.6
59.6
48.7
40.0
8.2
10.1
8.6
8.6
11.8
10.6
11 • 2
15.6
11 .8
12.3
10.5
9.7
59
69
65
61
49
48
41
40
41
37
46
57
5
4
8
5
3
5
5
4
9
6
9
Summer
Fall
Win ter
Spring
1959
1959
1959-60
1960
54
49
41
44
5
7
5
8
43.3
51.7
59.)
50.8
9.5
11 • 5
14.4
13.4
64
51
40
46
7
9
5
11
6
46.
TABLE B-3
Mean and Standard Deviation of Monthly and Seasonal
Positions of the Arctic Jet Stream and the -31C
Isotherm at 500 mb with the Mean and Standard
Deviation of the Zonal Wind Speed of the Jet
Stream Core
Mon th
Jet Stream
Latitude
Core Speed
(mps)
Mean
S.D.
Mean
s.n.
3.2
June
July
August
September
October
November
December
January
February
Mar ch
April
May
1959
1959
1959
1959
1959
1959
1959
1960
1960
1960
1960
1960
72
86
79
69
63
49
61
56
64
55
60
61
11
0
0
4
3
4
13
6
5
6
8
34.9
32.5
37.5
42.5
42.0
41.6
40.4
42.0
37.9
43.6
36.8
41.8
Summer
Fall
Win ter
Spring
1959
1959
1959-60
1960
76
59
59
59
9
9
11
8
35.0
42.0
40.9
41.1
8
Isotherm
Latitude
Mean
s.D.
63
5
5.0
6.9
7.6
8.5
7.3
8.6
7.0
9.3
7.7
5.6
82
70
59
50
54
52
56
43
57
74
0
5
6
6
8
10
9
10
4.0
7.8
8.1
7.8
67
58
54
57
8
9
9
14
.o
8
7
47.
TABLE B-4
Mean and Standard Deviation of Monthly and Seasonal
Positions of the Polar-Night Jet Stream and the -60C
Isotherm at 50 mb with the Mean and Standard
Deviation of the Zonal Wind Speed of the Jet
Stream Core
Mon th
June
July
August
September
Ootober
November
December
January
February
March
April
May
1959
1959
1959
1959
1959
1959
1959
1960
1960
1960
1960
1960
Summer
Fall
Win ter
Spring
1959
1959
1959-60
1960
Jet Stream
Latitude
Core S)eed
(mps
Mean
Mean
S.D.
s.n.
!sotherm
Latitude
Mean
S.D.
68
59
70
54
72
66
49
62
66
65
8
6
6
5
7
2
37.0
39.3
39.1
43.8
40.2
46.6
35.0
8.1
5.6
7.5
12.5
9.0
1o. 5
2.5
77
61
67
62
71
67
6
9
12
12
7
10
8
12
7
38.5
40.3
45.6
6.6
9.9
1o. 5
67
67
67
11
8
7
12
48.
APPENDIX C
List of Upper Air Stations Along 80 Degrees West
Supplying Basic Data for the Cross-Sections
Identifier
Latitude
Albrook (Balboa, c .z.)
78806
80 58'
79° 33'
Swan Island
78501
17° 24 t
83° 56'
Miami, Fla.
72202
25° 49'
80° 17'
Jacksonville, Fla.
72206
30° 25'
81° 39 t
s.e.
72208
32° 54'
80° 02'
Greensboro, N.. C.
72317
36° 05'
79° 57'
Washington, D.C.
72405
38° 51
t
77° 02'
Buffalo, N.Y.
72528
43° 07'
78° 55'
72734
46° 28'
84° 22'
Moosonee, Ont.
72836
51° 16'
80° 39'
Port Harrison, Que.
72907
58° 27'
78° 08'
Coral Harbour, N.W.T.
Hall Beach, N.W.T. 1 )
72915
64° 12'
83° 22'
74081
68° 47'
81° 15'
Resolute, N.W.T.
72924
74° 43'
94° 59'
Alert, N.W.T.
74082
82° 30'
62° 20'
Name
Charleston,
Sault Ste Marie,
Mi ch.
1 ) Formerly known as Hall Lake, N.W.T.
Longitude