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P27
Piia Post
University of Tartu
Institute of Physics
P27 - a simple eigenvector based classification scheme (Kruizinga
1978, 1979)
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Uses only 500 hPa heights on a regular grid (original one 6 x 6
points with the step of 5° in latitude and 10° in longitude)
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ptq= htq - ht , q=1,... n; n – the number of gridpoints,
t=1,...N, N – the number of days
The vector of 500 hPa heights is approximated as:
 pt ≈ s1t a1+ s2t a2 + s3t a3
 a-s are the first principal component vectors (eigenvectors of the
second-moment matrix of pt) and s-s are their amplitudes or
scores.
The flow pattern of a particular day is described by three
amplitudes: s1t, s2t, s3t

s1ta1 characterizes the east-west component of
the flow
s2ta2 – the north-south component and
s3ta3 – the cyclonicity (or anticyclonicity)
The range of each amplitude is divided into three
equiprobable intervals, then each pattern is on
the basis of its amplitudes uniquely assigned to
one of
the 3 x 3 x 3 = 27 possible interval combinations.
1) Which parameters are used for the calculations?
500 hPa gph
2) Is a specific program/software available for the application and use of the
method, or a program must be developed by the user? Is code
reproducible?
No special software needed. Code is reproducible.
3) Must the researcher have a computer programming background for the
application of the method (e.g. in order to develop software)?
A little, if to compute the types himself.
4) How much time and computer power is roughly required for the
computations?
5) Which method is used for deciding the number of classes/patterns? Is any
number possible?
The number is decided earlier, depends how many principal components
are taken into account and to how many probability classes they are
divided.
6) List the 5 main articles related to this method
Kruizinga, S., 1979. Objective classification of daily 500 mbar patterns.
Preprints Sixth Conference on Probability and Statistics in Atmospheric
Sciences, 9-10 October 1979, Banff, Alberta, American Meteorological
Society, Boston, MA, 126-129.
Buishand, T.A., Brandsma, T., 1997. Comparison of circulation classification
schemes for predicting temperature and precipitation is the Netherlands. Int.
J. Climatol., 17, 875-889.
7) How are key-patterns defined?
Just first three components
8) Which distance/similarity measure is used (possible)?
Usual Euclidian distance
Hemispheric circulation
patterns
Dzerdzeevski (1968)
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Elementary circulation mechanisms (ECM)
operate over a short time interval and govern the
circulation pattern over the entire hemisphere
2 postulates:
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The hemispheric circulation is determined by a finite
number of characteristic circulation mechanisms. The
number of mechanisms is small over short time period, but
their characteristics differ greatly with season.
The features of each circulation mechanism persist longer
than the time scale of synoptic processes. Hemispheric
circulation is a real macroprocess, not a chance
combination of indipendent synoptic processes. Individual
disturbances and fronts are regarded as ‘noise’.
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Cyclone and anticyclone tracks at the 700 or
500 hPa level are used as an indicator of the
main mid-tropospheric steering currents.
Charts averaged over several days provide
the best view of the various types.
Special attention is given to polar intrusions
and associated blocking in the westerlies in
six hemspheric sectors of 50-60°.
Vangengeim (1935, 1946)
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Elementary synoptic processes
Three basic types of circulation:
W – westerly
E – easterly
C – meridional
Each type is characterized by a particular
distribution of depressions and anticyclones
at the surface and by an organization of the
major long wave pattern
1996
1991
1986
1981
1976
1971
1966
1961
1956
1951
1946
1941
1936
1931
1926
1921
1916
1911
1906
1901
1896
1891
Frequency of occurrence of circulation
types (in days) 1891-1998
300
250
200
W
150
E
C
100
50
0