Objective classification of Australian climates

Abstract

Köppen's scheme to classify world climates was devised in 1918 by Dr Wladimir Köppen of the University of Graz in Austria. Over the decades it has achieved wide acceptance amongst climatologists. However, the scheme has also had its share of critics, who have challenged the scheme's validity on a number of grounds. For example, Köppen's rigid boundary criteria often lead to large discrepancies between climatic subdivisions and features of the natural landscape. Furthermore, whilst some of his boundaries have been chosen largely with natural landscape features in mind, other boundaries have been chosen largely with human experience of climatic features in mind. The present paper presents a modification of Köppen's classification that addresses some of the concerns and illustrates this modification with its application to Australia.

Full text

Introduction
Köppen’s scheme to classify world climates was
devised in 1918 by Dr Wladimir Köppen of the
University of Graz in Austria (Köppen 1931; Köppen
and Geiger 1928, 1930-39). This paper presents a
modification of Köppen’s scheme.
The Köppen classification is based on the concept
that native vegetation is the best expression of cli-
mate, climate zone boundaries having been selected
with vegetation limits in mind (Trewartha 1943). The
classification may be applied to present-day climatic
conditions. Alternatively, it also may be used to
develop a future climatology that is implied by the
output of a numerical climate model (Löhmann et al.
1993) – although the reliability of such a future cli-
matology would be dependent upon the reliability of
the numerical climate model output.
Köppen recognises five principal groups of world
climates that are intended to correspond with five
principal vegetation groups. These five climatic
groups may be described as tropical rainy, dry, tem-
perate rainy, cold snowy forest, and polar.
The dry climates are defined on the basis of there
being an excess of evaporation over precipitation
(which is determined from the mean annual tempera-
ture and the mean annual rainfall). The tropical rainy
Aust. Met. Mag. 49 (2000) 87-96
Objective classification of Australian
climates
Harvey Stern and Graham de Hoedt
Bureau of Meteorology, Melbourne, Australia
and
Jeneanne Ernst
Technische Fachhochschule, Berlin, Germany
(Manuscript received July 1999; revised December 1999)
Köppen’s scheme to classify world climates was devised in 1918
by Dr Wladimir Köppen of the University of Graz in Austria.
Over the decades it has achieved wide acceptance amongst cli-
matologists. However, the scheme has also had its share of crit-
ics, who have challenged the scheme's validity on a number of
grounds. For example, Köppen’s rigid boundary criteria often
lead to large discrepancies between climatic subdivisions and
features of the natural landscape. Furthermore, whilst some of
his boundaries have been chosen largely with natural landscape
features in mind, other boundaries have been chosen largely
with human experience of climatic features in mind. The pre-
sent paper presents a modification of Köppen’s classification
that addresses some of the concerns and illustrates this modifi-
cation with its application to Australia.
87
Corresponding author address: Harvey Stern, Victorian Regional
Office, Bureau of Meteorology, Box 1636M, Melbourne, Vic. 3001,
Australia.
e-mail: H.Stern@bom.gov.au

climates are climates, as yet unclassified, with a mean
temperature of the coolest month of at least 18°C.
The polar climates are climates, as yet unclassified,
with a mean temperature of the warmest month of
below 10°C. The cold snowy forest climates are cli-
mates, as yet unclassified, with a mean temperature of
the coolest month of below -3°C. Remaining climates
are defined as temperate rainy.
Each of these climates is further divided into sub-
divisions based upon differences in the seasonal dis-
tribution of temperature and precipitation. For exam-
ple, Köppen climates with distinctly dry winters are
defined as those temperate rainy climates and cold
snowy forest climates with at least ten times as much
rain in the wettest summer month as in the driest win-
ter month. Trewartha (1943) presents a full descrip-
tion of all of the subdivisions and provides a detailed
map depicting the distribution around the globe of the
original Köppen climates.
The purpose of this paper is two-fold. Firstly, a
new modification of Köppen’s classification of world
climates is presented. Secondly, the modification is
illustrated with its application to Australia.
Discussion
Trewartha (1943) notes that Köppen’s classification
has been criticised from ‘various points of view’
(Thornthwaite 1931; Jones 1932; Ackerman 1941).
Rigid boundary criteria often lead to large discrepan-
cies between climatic subdivisions and features of the
natural landscape. Some boundaries have been cho-
sen largely with natural landscape features in mind
(for example, ‘rainforest’), whilst other boundaries
have been chosen largely with human experience of
climatic features in mind (for example, ‘monsoon’).
Trewartha (1943) acknowledges the validity of these
criticisms when he writes that ‘climatic boundaries, as
seen on a map, even when precisely defined, are nei-
ther better nor worse than the human judgements that
selected them, and the wisdom of those selections is
always open to debate’. He emphasises, however,
that such boundaries are always subject to change
‘with revision of boundary conditions … (and that) …
such revisions have been made by Köppen himself
and by other climatologists as well’.
Nevertheless, the telling evidence that the Köppen
classification's merits outweigh its deficiencies lies in
its wide acceptance. Trewartha (1943) observes that
‘its individual climatic formulas are almost a common
language among climatologists and geographers
throughout the world … (and that) … its basic princi-
ples have been … widely copied (even) by those who
have insisted upon making their own empirical classi-
fications’. Trewartha's (1943) comments are as rele-
vant today as they were half a century ago (see, for
example, Müller (1982); Löhmann et al. (1993)).
For the above reasons, in modifying the Köppen
classification (Figs 1 and 2), the authors have chosen
to depart only slightly from the original.
Nevertheless, the additional division of some of the
Köppen climates and some recombining of other
Köppen climates may better reflect human experience
of significant features. In recognition of this, the fol-
lowing changes, which are also summarised in Table
1, have been adopted in this work:
(1) The former tropical group is now divided into two
new groups, an equatorial group and a new tropi-
cal group. The equatorial group corresponds to
the former tropical group's isothermal subdivi-
sion. The new tropical group corresponds to that
remaining of the former tropical group. This is
done to distinguish strongly between those cli-
88 Australian Meteorological Magazine 49:2 June 2000
Table 1. A summary of key differences between Köppen's original scheme and the new scheme.
Köppen's original scheme New scheme
Tropical group Divided into equatorial & tropical groups
Monsoon subdivision Becomes rainforest (monsoonal) subdivision
Dry group Divided into desert & grassland groups
Summer/winter drought subdivisions Now requires 30+mm in wettest month
Temperate group Divided into subtropical & temperate groups
Cold-snowy-forest group Cold group
Dry summer/winter subdivisions Moderately dry winter subdivision added
Polar group Maritime subdivision added
Frequent fog subdivision Applies now only to the desert group
Frequent fog subdivision Becomes high humidity subdivision
High-sun dry season subdivision Absorbed into other subdivisions
Autumn rainfall max subdivision Absorbed into other subdivisions
Other minor subdivisions Absorbed into other subdivisions

mates with a significant annual temperature cycle
from those climates without one (although this
feature is not as marked in the Australian context,
as elsewhere in the world). Under this definition
some climates, distant from the equator, are clas-
sified as equatorial. This is considered acceptable
as that characteristic is typical of climates close to
the equator. Figure 1 shows that, in Australia,
equatorial climates are confined to Queensland's
Cape York Peninsula and the far north of the
Northern Territory.
(2) The equatorial and tropical group monsoon sub-
divisions are re-named as rainforest (monsoonal)
subdivisions. This is done because, in these sub-
divisions, the dry season is so short, and the total
rainfall is so great, that the ground remains suffi-
ciently wet throughout the year to support rain-
forest. Figure 2 shows that, in Australia, rainfor-
est subdivisions are found along sections of the
northern part of Queensland's east coast.
(3) The former dry group is now divided into two
new groups, a desert group and a grassland group.
The new groups correspond to the former desert
and steppe subdivisions of the dry group. This is
believed necessary because of the significant dif-
ferences between the types of vegetation found in
deserts and grasslands. That there is a part of cen-
tral Australia covered by the grassland group of
climates (Fig. 1) is a consequence of the higher
rainfall due to the ranges in that region.
(4) The new desert and grassland winter drought
(summer drought) subdivisions now require the
additional criterion that there is more than 30
mm in the wettest summer month (winter month)
to be so classified. This change is carried out
because drought conditions may be said to pre-
vail throughout the year in climates without at
least a few relatively wet months. It should be
noted that the original set of Köppen climates
employed the phrases ‘winter drought’ and ‘sum-
mer drought’ to respectively describe climates
that are seasonally dry. Figure 2 shows that the
summer drought subdivisions are found in the
southern half of the country, whilst the winter
drought subdivisions are found in the northern
half of the country.
(5) The former temperate group is divided into two
new groups, a temperate group and a subtropical
group. The new subtropical group corresponds
to that part of the former temperate group with a
mean annual temperature of at least 18°C. The
new temperate group corresponds to that part of
the former temperate group remaining. This is
done because of the significant differences in the
vegetation found in areas characterised by the
two new groups, and in order that there is conti-
nuity in the boundary between the hot and warm
desert and grassland climates where they adjoin
rainy climates. Figure 1 shows that a large
region, covering much of southeast Queensland
and some elevated areas further north, is now
characterised as subtropical.
(6) For simplicity, the former Köppen cold snowy
forest group of climates is re-named as the cold
group. Figure 1 shows that this climate is not
found on the Australian mainland or in Tasmania.
(7) For the temperate, subtropical, and the cold
groups, the distinctly dry winter subdivision
requires the additional criterion of no more than
30 mm in the driest winter month to be so classi-
fied. In order that there be consistency between
the criteria for the distinctly dry winter and the
distinctly dry summer subdivisions, this is
thought to be a worthwhile change. Figure 2
shows that, whereas that part of Western
Australia characterised as subtropical has a dis-
tinctly dry summer, much of subtropical south-
east Queensland has no distinctly dry season.
(8) Carved out of the temperate, subtropical, and the
cold groups with no distinctly dry season subdi-
vision is the moderately dry winter subdivision.
This new subdivision receives at least three times
(but less than ten times) the rainfall in the driest
winter month. This subdivision has been added
in order that there be a match with that part of the
distinctly dry summer subdivision that was not
matched by the distinctly dry winter subdivision.
Figure 2 shows that parts of subtropical southeast
Queensland have a moderately dry winter.
(9) The polar group has added to it the subdivision
polar maritime, this subdivision reflecting the
climate of the sub-antarctic islands, which other-
wise would have been classified (inappropriate-
ly) as polar tundra. Polar tundra would be an
inappropriate description for climates where the
average temperature of the coldest month is -3°C
or above. This is because, with the temperature
not well below freezing, it is difficult for the
ground to become frozen (a characteristic of
‘polar tundra’). Figure 1 shows that this climate
is not found on the Australian mainland or in
Tasmania.
(10) The frequent-fog desert and grassland climates
are re-named as high-humidity climates. They
are also defined in terms of mean annual relative
humidity, rather than in terms of fog frequency.
This is on account of the dew-fall that results
from the high humidity being a significant con-
tributor to plant moisture in regions with such
climates. They are also restricted to desert cli-
Stern et al.: Objective classification of Australian climates 89

90 Australian Meteorological Magazine 49:2 June 2000
Fig. 1 The key climate groups.
ClimateClassification
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Stern et al.: Objective classification of Australian climates 91
Fig. 2 Subdivisions within the key climate groups.
C li m a te C la ss if ic at io n
o f A u st ra lia
Equatorial
Tropical
Subtropical
Desert
Grassland
Temperate
rainforest (monsoonal)
savanna
rainforest (persistently wet)
rainforest (monsoonal)
savanna
no dry season
distinctly dry summer
distinctly dry winter
moderately dry winter
hot (persistently dry)
hot (summer drought)
hot (winter drought)
warm (persistently dry)
hot (persistently dry)
hot (summer drought)
hot (winter drought)
warm (persistently dry)
warm (summer drought)
no dry season (hot summer)
moderately dry winter (hot summer)
distinctly dry (and hot) summer
no dry season (warm summer)
moderately dry winter (warm summer)
distinctly dry (and warm) summer
no dry season (mild summer)
distinctly dry (and mild) summer
no dry season (cool summer)
Based on a modified Koeppen classification system.
Classification derived from 0.025 x 0.025 degree resolution mean
rainfall, mean maximum and mean minimum temperature gridded data.
All means based on a standard 30-year climatology (1961 to 1990).

mates. This is on account of the dew-fall in
grassland climates not being a significant mois-
ture contributor (in comparison with the total
rain that falls in grassland climates). Whereas
this climate subdivision is found in the desert
regions on the west coasts of the other two
southern hemisphere continents, the relative
humidity in the west coast desert region of
Australia is far too low for the climate to be
characterised as high humidity.
(11) Some equatorial and tropical subdivisions (those
equatorial and tropical climates with an autumn
rainfall maximum, those with a high-sun dry sea-
son, and those with a hottest month prior to the
summer solstice) are considered to be minor and
have therefore been absorbed into the other equa-
torial and tropical subdivisions.
(12) Some subtropical and temperate subdivisions
(those subtropical and temperate climates that
are isothermal, those that have a hottest month
prior to the summer solstice, and those with a
late-spring/early-summer rainfall maximum) are
also considered to be minor and have therefore
been absorbed into other subtropical and temper-
ate subdivisions.
Method of analysis
The above issues have been addressed in preparing
the new climate classification. The new climate clas-
sification is defined in the Appendix. It is illustrated
over Australia in Fig. 1, which presents the key cli-
mate groups, and Fig. 2, which presents the subdivi-
sions within those groups. Figures 1 and 2 may be
contrasted with the presentation of Köppen's original
scheme, as depicted by Trewartha (1943). Although
many features are depicted in a similar manner in both
the old and new schemes, the detail is greatly
enhanced in the new scheme.
A previous paper by the present authors (Stern et
al. 1999) depicted an analysis of climate groups and
subdivisions over Australia. That analysis, also as
defined in the Appendix, is based on a ‘smoothed’ 25
km grid spacing. That paper employed the Barnes
analysis technique, as modified and described by
Jones and Weymouth (1997). However, the disad-
vantages of that approach were that the smoothing
was too great to allow depiction of some of the very
fine detail, and that the Barnes approach does not ade-
quately reflect the impact of altitude in sparse data
and mountainous areas.
The present paper's analyses are generated using
Hutchinson’s interpolation method of thin plate
smoothing splines (Hutchinson 1995). The analysis
and interpolation are done in three dimensions, incor-
porating elevation as well as latitude and longitude, at
a resolution of 0.025 degrees. The interpolated (grid-
ded) data are then smoothed using a one-pass 13x13
binomial smoother.
The gridded data are based on the Australian
Bureau of Meteorology's (BoM) mean monthly rain-
fall, mean annual rainfall, mean maximum tempera-
ture, and mean minimum temperature gridded
datasets (39 gridded datasets in total), the datasets
forming part of an updated Australian rainfall and
temperature climatology. Humidity data were not
available in gridded form but, because no Australian
desert station's humidity data came close to satisfying
the ‘humid’ criterion, it was assumed that no
Australian desert climate should be classified as
‘humid’. Station data used to generate the gridded
datasets were extracted from the BoM's national cli-
mate database, ADAM (Australian Data Archive for
Meteorology). The data extracted from ADAM,
approximately 6000 sites with rainfall data and
approximately 600 sites with temperature data, con-
formed to the WMO (World Meteorological
Organization) guidelines for the quality and continu-
ity of data used in climatological analyses (WMO
1989). Also, in keeping with the WMO guidelines,
the 30-year period 1961–1990 was used as the stan-
dard averaging period. The 39 smoothed rainfall and
temperature grids are then objectively combined (on a
gridcell by gridcell basis) according to the rules for
classification.
One possible deficiency of the approach may arise
if an inappropriate grid length is used. For example, if
the grid length is too large, important detail may be
lost; by contrast, if the grid length is too small, unim-
portant detail may clutter the maps.
A second possible deficiency is that in some parts
of Australia, notably central Australia, observation
sites are well scattered, although the statistical tech-
nique used largely overcomes the impact of this defi-
ciency by taking into account the influence of topo-
graphical features of the landscape.
Summary and conclusion
A modification of the Köppen classification of world
climates has been presented. The extension has been
illustrated by its application to Australian climates.
Even with the additional complexity, the final classi-
fication contains some surprising homogeneity. For
example, there is a common classification between
the coastal areas of both southern Victoria and south-
ern New South Wales. There is also the identical clas-
sification of western and eastern Tasmania. This aris-
92 Australian Meteorological Magazine 49:2 June 2000

es due to the classification not identifying every cli-
mate variation because a compromise has to be
reached between sacrificing either detail or simplici-
ty. For example, regions with only a slight annual
cycle in rainfall distribution do not have that variation
so specified in the classification. Similarly, regions
with only slightly different mean annual temperatures
are sometimes classified as being of the same climate.
The classification descriptions need to be concise,
for ease of reference. As a result, the descriptions are
not always complete. For example, the word ‘hot’ is
used in reference to those deserts with the highest
annual average temperatures, even though winter
nights, even in hot desert climates, can't realistically
be described as ‘hot’.
In conclusion, the authors see the classification
assisting in the selection of new station networks.
There is also the potential for undertaking subsequent
studies that examine climate change in the terms of
shifts in climate classification boundaries by using
data from different historical periods, and by using
different characteristics to define climate type such as
‘inter-annual variability of precipitation’. In the
future, it is planned to prepare climate classification
maps on a global scale, as well as on a regional
Australian scale.
Acknowledgments
The authors take great pleasure in acknowledging the
valuable contributions to their work made by Bureau
of Meteorology colleagues. In particular, we thank
colleagues in the National Climate Centre, in
Regional Climate and Consultancy Sections and in
the Victorian Regional Office.
Dr William Wright of the National Climate Centre
provided the authors with the gridded datasets upon
which the analyses were based.
The work was originally inspired by a discussion
between Mr Tom Garnett of Blackwood's Garden of
St Erth, who saw the potential application of climate
classification to his industry, and the lead author.
Finally we thank the two Australian
Meteorological Magazine reviewers (Terry Skinner
and an unknown reviewer), and Associate Editor Neil
Plummer, for their helpful suggestions.
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Stern et al.: Objective classification of Australian climates 93

94 Australian Meteorological Magazine 49:2 June 2000
Appendix
Defining the climate groups and subdivisions.
The source data upon which the classification is based
↓
↓
↓
Defining the derived data and classification criteria
↓
↓
↓(defining the Temperature elements)
↓
↓(defining the Temperature criteria)
↓
↓(defining the Precipitation elements)
↓
↓(defining the Precipitation criteria)
↓
↓(defining the Humidity element)
↓
↓(defining the Humidity criterion)
↓
↓
Where →min1, max1, rn1, rh1; min2, max2, rn2, rh2; etc., represent the mean minimum temperature, maximum tempera-
ture, total rainfall and relative humidity of Jan., Feb., etc.
tm1=(min1+max1)/2 tm2=(min2+max2)/2 etc.
ta= (tm1+tm2+ … +tm12)/12 tw= max(tm1,tm2, … ,tm12) tc= min(tm1,tm2, … ,tm12)
t1= (tw-tc)lt5 t2= (ta)ge18 t3= (tw)ge18 t4= (tw)ge22 t5= (tw)ge10 t6= (tw)ge0
t7= ((((tm1)ge10)+ … +((tm12)ge10))gt3) t8= (tc)ge18 t9= (tc)ge-3 t10= (tc)ge -38
h= (rh1+ rh2+ … + rh12)/12
h1= (h)gt70
p1= ((rds)le30 and (rww)gt30 and (rww)ge(3*(rds))) and not ((rws)ge(10*(rdw)))
p2= ((rdw)le30 and (rws)gt30 and (rws)ge(10*(rdw))) and not ((rww)ge(3*(rds)))
p3= (ra)lt(10*(ta)) p4= (ra)lt(10*((ta)+7)) p5= (ra)lt(10*((ta)+14)) p6= (ra)lt(20*(ta))
p7= (ra)lt(20*((ta)+7)) p8= (ra)lt(20*((ta)+14)) p9= (rd)lt60 p10 = (rd)lt(100-(ra/25))
p11= not (((p2) and (p5)) or ((p1) and (p3)) or ((p4) and not ((p1) or (p2))) or ((p2) and (p8) and not (p5)) or ((p1) and (p6)
and not (p3)) or ((p7) and not ((p1) or (p2) or (p4))))
p12= ((rws)ge(3*(rdw))) and ((rdw)le30) and not ((rww)ge(3*(rds)))
p13= (rwau) gt max(rws, rww) and (rwsp) gt max(rws, rww)
ra= (rn1+rn2+ … +rn12)
rw= max(rn1,rn2,..rn12) rd= min(rn1,rn2,..rn12) rws= max(rn12,rn1,rn2) rds=min(rn12,rn1,rn2)
rww= max(rn6,rn7,rn8) rdw= min(rn6,rn7,rn8)
rwau= max(rn3,rn4,rn5) rwsp=max(rn9,rn10,rn11)

Stern et al.: Objective classification of Australian climates 95
Defining the climate classes
↓
↓(generating the Desert climates)
↓
↓(generating the Grassland climates)
↓
↓(generating the Equatorial climates)
↓
↓(generating the Tropical climates)
↓
↓(generating the Subtropical climates)
↓
↓(generating the Temperate climates)
de1= [p4 and not(p1 or p2 or h1)] and t2 = hot (persistently dry)
de2= [p1 and p3 and not(h1)] and t2 = hot (summer drought)
de3= [p2 and p5 and not(h1)] and t2 = hot (winter drought)
de4= [p4 and not(p1 or p2 or h1)] and [t3 and not(t2)] = warm (persistently dry)
de5= [p1 and p3 and not(h1)] and [t3 and not(t2)] = warm (summer drought)
de6= [p2 and p5 and not(h1)] and [t3 and not(t2)] = warm (winter drought)
de7 = [p4 and not(p1 or p2 or h1)] and [t5 and not(t3)] = cool (persistently dry)
de8 = [p1 and p3 and not(h1)] and [t5 and not (t3)] = cool (summer drought)
de9 = [p2 and p5 and not(h1)] and [t5 and not(t3)] = cool (winter drought)
de10 = [h1] and [{p4 and not(p1 or p2)} or {p1 and p3} or {p2 and p5}] = humid
gr1= [p7 and not(p1 or p2 or h1)] and t2 = hot (persistently dry)
gr2= [p1 and p6 and not(h1)] and t2 = hot (summer drought)
gr3= [p2 and p8 and not(h1)] and t2 = hot (winter drought)
gr4= [p7 and not(p1 or p2 or h1)] and [t3 and not(t2)] = warm (persistently dry)
gr5= [p1 and p6 and not(h1)] and [t3 and not(t2)] = warm (summer drought)
gr6= [p2 and p8 and not(h1)] and [t3 and not(t2)] = warm (winter drought)
gr7 = [p7 and not(p1 or p2 or h1)] and [t5 and not(t3)] = cool (persistently dry)
gr8 = [p1 and p6 and not(h1)] and [t5 and not (t3)] = cool (summer drought)
gr9 = [p2 and p8 and not(h1)] and [t5 and not(t3)] = cool (winter drought)
eq1= [t1 and t8] and [p11 and not(p9)] = rainforest (persistently wet)
eq2= [t1 and t8] and [p9 and p11 and not(p10 or p13)] = rainforest (monsoonal)
eq3= [t1 and t8] and [p9 and p11 and p13 and not(p10)] = rainforest(double monsoonal)
eq4= [t1 and t8] and [p9 and p10 and p11] = savanna
tr1= [t8 and not(t1)] and [p11 and not(p9)] = rainforest (persistently wet)
tr2= [t8 and not(t1)] and [p9 and p11 and not(p10)] = rainforest (monsoonal)
tr3= [t8 and not(t1)] and [p9 and p10 and p11] = savanna
st1= [t2 and not(t8)] and [not(p1 or p2 or p7 or p12)] = no dry season
st2= [t2 and not(t8)] and [p12 and not(p1 or p2 or p7)] = moderately dry winter
st3= [t2 and not(t8)] and [p2 and not(p8)] = distinctly dry winter
st4= [t2 and not(t8)] and [p1 and not(p6)] = distinctly dry summer
te1= [t4 and t9 and not(t2)] and [not(p1 or p2 or p7 or p12)] = no dry season (hot summer)
te2= [t4 and t9 and not(t2)] and [p12 and not(p1 or p2 or p7)] = moderately dry winter (hot summer)
te3= [t4 and t9 and not(t2)] and [p2 and not(p8)] = distinctly dry winter (hot summer)
te4= [t4 and t9 and not(t2)] and [p1 and not(p6)] = distinctly dry (and hot) summer
te5= [t3 and t9 and not(t4)] and [not(p1 or p2 or p7 or p12)] = no dry season (warm summer)
te6= [t3 and t9 and not(t4)] and [p12 and not(p1 or p2 or p7)] = moderately dry winter (warm summer)
te7= [t3 and t9 and not(t4)] and [p2 and not(p8)] = distinctly dry winter (warm summer)
te8= [t3 and t9 and not(t4)] and [p1 and not(p6)] = distinctly dry (and warm) summer
te9= [t7 and t9 and not(t3)] and [not(p1 or p2 or p7 or p12)] = no dry season (mild summer)
te10= [t7 and t9 and not(t3)] and [p12 and not(p1 or p2 or p7)] = moderately dry winter (mild summer)
te11= [t7 and t9 and not(t3)] and [p2 and not(p8)] = distinctly dry winter (mild summer)
te12= [t7 and t9 and not(t3)] and [p1 and not(p6)] = distinctly dry (and mild) summer
te13= [t5 and t9 and not(t7)] and [not(p1 or p2 or p7 or p12)] = no dry season (cool summer)
te14= [t5 and t9 and not(t7)] and [p12 and not(p1 or p2 or p7)] = moderately dry winter (cool summer)
te15= [t5 and t9 and not(t7)] and [p2 and not(p8)] = distinctly dry winter (cool summer)
te16= [t5 and t9 and not(t7)] and [p1 and not(p6)] = distinctly dry (and cool) summer

96 Australian Meteorological Magazine 49:2 June 2000
↓
↓(generating the Cold climates)
↓
↓(generating the Polar climates)
co1= [t4 and t10 and not(t2 or t9)] and [not(p1 or p2 or p7 or p12)] = no dry season
(hot summer)
co2= [t4 and t10 and not(t2 or t9)] and [p12 and not(p1 or p2 or p7)] =moderately dry winter (hot summer)
co3= [t4 and t10 and not(t2 or t9)] and [p2 and not(p8)] = distinctly dry winter (hot summer)
co4= [t4 and t10 and not(t2 or t9)] and [p1 and not(p6)] = distinctly dry (and hot) summer
co5= [t3 and t10 and not(t4 or t9)] and [not(p1 or p2 or p7 or p12)] = no dry season
(warm summer)
co6= [t3 and t10 and not(t4 or t9)] and [p12 and not(p1 or p2 or p7)] = moderately dry winter (warm summer)
co7= [t3 and t10 and not(t4 or t9)] and [p2 and not(p8)] = distinctly dry winter (warm summer)
co8= [t3 and t10 and not(t4 or t9)] and [p1 and not(p6)] = distinctly dry (and warm) summer
co9= [t7 and t10 and not(t3 or t9)] and [not(p1 or p2 or p7 or p12)] = no dry season
(mild summer)
co10= [t7 and t10 and not(t3 or t9)] and [p12 and not(p1 or p2 or p7)] = moderately dry winter (mild summer)
co11= [t7 and t10 and not(t3 or t9)] and [p2 and not(p8)] = distinctly dry winter (mild summer)
co12= [t7 and t10 and not(t3 or t9)] and [p1 and not(p6)] = distinctly dry (and mild) summer
co13= [t5 and t10 and not(t7 or t9)] and [not(p1 or p2 or p7 or p12)] = no dry season
(cool summer)
co14= [t5 and t10 and not(t7 or t9)] and [p12 and not(p1 or p2 or p7)] = moderately dry winter (cool summer)
co15= [t5 and t10 and not(t7or t9)] and [p2 and not(p8)] = distinctly dry winter (cool summer)
co16= [t5 and t10 and not(t7 or t9)] and [p1 and not(p6)] = distinctly dry (and cool) summer
co17= t5 and not (t10) = very severe winter
po1= t6 and t9 and not(t5) = maritime
po2= t6 and not(t5 or t9) = tundra
po3= not(t6) = perpetual frost