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APRIL 21, 1923] 
; NO much less important among the geographical 
factors which determine climate than latitude 
and altitude, is the relative distribution of land and 
sea, or, in short, continentality versus oceanity, and 
in view of the somewhat large class of students who 
encounter this aspect of climatology it seems desirable 
to direct attention to a couple of German maps which 
have recently appeared indicating the distribution of 
continentality over the globe as a whole and over 
Europe in detail (Petermanns Mitteilungen, June 1922, 
R. Spitaler after G. Swobodna). 
It is possible to represent the mean or normal 
temperature of a particular latitude at any time of 
the year in an equation involving, also, the intensity 
of insolation and the relative distribution of land and 
water in the neighbourhood ; and therefore it comes 
about that there is a means of seeing how the tempera- 
ture of a given point in summer, winter, or the year 
as a whole, compares, on one hand, with full “‘ con- 
tinentality ’’ such as would uniformly prevail over a 
hemisphere covered entirely with land, or, on the 
her hand, with full ‘‘ oceanity’’ such as would 
characterise an entire water hemisphere. The maps 
question are based upon the annual range of air 
temperature between January and July, but are not 
quite the same thing as simple maps of equal annual 
ange would be, because the annual range is to some 
sxtent affected by differences of latitude which are 
allowed for in the relationship just referred to. 
Taking full ‘‘continentality’’ as roo, and full 
oceanity ’’ as o (zero “‘ continentality ’’), lines of 
equal percentage value are drawn: across the entire 
ap of the world except the inter-tropical belt, 
uncertainty for which attaches to the fact that the 
gnificance of the seasons is not the same as it is. in 
extra-tropical latitudes. 
There is a large area in the interior of North 
America with 90 per cent. continentality, the Sahara 
region and much of Western Asia with 100, and a 
considerable portion of Eastern Asia suffering from 
a super-continentality amounting to as much as 130. 
This is explained by the abnormal winter cold of 
Central Asia, due to a certain type of atmospheric 
sirculation set up over this great land-mass, which 
esults in a local degree of continentality greater than 
at proper to a uniform land hemisphere. A high 
degree of continentality also prevails over the land- 
locked North Polar basin where the ice-covering 
aises the percentage of the Arctic Ocean to near 100. 
At the other end of the scale we find 5 per cent. (95 
per cent. oceanity) over that part of the North 
Atlantic between Iceland and Norway, and o (full 
pceahity) over much of the oceanic areas in the 
Southern Hemisphere, while local regions in the South 
Pacific and the Southern Ocean, under a special trend 
of sea and air currents, experience a slight degree of 
super-oceanity amounting to -5 per cent. on the 
continentality scale (105 oceanity). In consequence 
of the circulation of the atmosphere there are regions 
where continentality trespasses upon the sea, e.g. the 
ellow Sea and Sea of Okhotsk with 70 per cent., and 
where oceanity invades the land, e.g. England and 
France with 20 to 45 per cent., values actually lower 
than that of the land-locked Mediterranean Sea, 
which averages about 45 per cent. 
It is clear, therefore, that these maps show some- 
thing more than the simple effect of local land and 
sea influences upon the annual range of temperature, 
and it would have been instructive to have a carto- 
| gtaphical representation of this effect as well, un- 
complicated by the effect due to the transference of 
continental and oceanic conditions beyond their 
respective domains. If one turns, for example, to 
NO. 2790, VOL. III | 
NATURE 
Climatic Continentality and Oceanity. 
By L. C. W. Bonacrna. 
the more detailed map of Europe, there is ro per cent. 
continentality along the west coasts of Ireland and 
Scotland, and the 50 per cent. line, marking the 
boundary between the ‘‘ continental ’’ and ‘‘ oceanic ”’ 
parts of the continent, driven back by the prevailing 
Atlantic winds to the longitude of eastern Germany 
except for outliers around Spain, Switzerland and 
Sweden. Even the neighbourhood of London, the 
most continental portion of the United Kingdom, has 
a percentage no higher than 27, and the generally low 
value, about 25 per cent. for England as a whole 
with a position fairly well balanced as between land 
and sea, unmistakably reflects the dominating 
influence of the prevailing oceanic winds. There can 
be little doubt, indeed, that if the south-east of 
England were normally controlled by a stagnant 
contracyclonic system of circulation allowing more 
local temperature controls to gain the ascendant, the 
continentality would rise to near 50 per cent., and to 
near 75 per cent. if the prevailing winds were con- 
tinental east winds instead of the actual oceanic west 
winds. This conclusion is strongly supported by the 
high degree of continentality, about 70 per cent., 
which prevails on the east coast of the United States 
in consequence of the westerly circulation from the 
interior of the continent. 
Instructive as these German maps are, they do no 
more than touch the fringe of the subject inasmuch 
as there are other criteria by which thermal con- 
tinentality may be judged, namely, diurnal range of 
temperature and the magnitude of irregular devia- 
tions from the normal, both of which run roughly, 
but not exactly, parallel with the seasonal or annual 
range above considered. It could be shown, for 
example, that in relation to the inland parts of 
England the east coast is somewhat more ‘“ con- 
tinental ’’ according to annual range than according 
to diurnal range of temperature. This is because the 
short-period range between day and night is more 
definitely influenced in the long run by local distance 
from the sea, whereas the seasonal range of tempera- 
ture is more markedly affected by continental types 
of weather, transporting summer heat or winter cold, 
on the east coast than it is farther west. 
Interesting, too, is the study of continentality from 
the point of view of deviations of particular seasons 
from the normal, and here a striking lesson is afforded 
by the climates of London and Paris. The French 
capital on the average of a long series of years is 
2° F, colder than the English in January and 3° F. 
hotter in July, the greater difference in summer being 
apparently due to the more southerly latitude, which 
would work with the continentality difference in the 
warm season but against it in the cold. Yet it is 
during occasional periods of severe cold that the more 
violent continentality of Paris is so emphatically 
demonstrated. The month of December, 1879, was, 
on the continental mainland, one of unparalleled 
rigour, the mean temperature day and night for the 
entire month in Paris being so low as 18° F., or some 
20° below the normal. But the coldest December 
ever recorded in London, that of 1890, a month of 
appalling gloom and as cold as any winter month 
that has occurred since the establishment of records, 
had a mean temperature not lower than 29° F., 
or only 10° below normal, while the same month 
in Paris was 12° below, or only less cold than 1879. 
There are many similar instances of wider departures 
from the normal on the other side of the Channel. 
Facts of this kind constitute an obtrusive aspect of 
climate, but they are apt to be eclipsed in the common 
practice of limiting one’s studies to means and 
averages. 
