eases from the interiors towards the
east coasts. In North America the distribution through the year is very
uniform, with some tendency to a summer maximum, as in the interior
(N.A, fig. 12).

In eastern Asia the winters are relatively dry and clear, under the
influence of the cold offshore monsoon, and the summers are warm and
rainy. Rainfalls of 40 in. are found on the east coasts of Korea,
Kamchatka and Japan, while in North America, which is more open, they
reach farther inland. Japan, although occupying an insular position, has
a modified continental rather than a marine climate. The winter monsoon,
after crossing the water, gives abundant rain on the western coast,
while the winter is relatively dry on the lee of the mountains, on the
east. Japan has smaller temperature ranges than the mainland.

_Mountain Climates._--The mountain climates of the temperate zone have
the usual characteristics which are associated with altitude everywhere.
If the altitude is sufficiently great the decreased temperature gives
mountains a polar climate, with the difference that the summers are
relatively cool while the winters are mild owing to inversions of
temperature in anticyclonic weather. Hence the annual ranges are smaller
than over lowlands. At such times of inversion the mountain-tops often
appear as local areas of higher temperature in a general region of
colder air over the valleys and lowlands. The increased intensity of
insolation aloft is an important factor in giving certain mountain
resorts their deserved popularity in winter (_e.g._ Davos and Meran). Of
Meran it has been well said that from December to March the nights are
winter, but the days are mild spring. The diurnal ascending air currents
of summer usually give mountains their maximum cloudiness and highest
relative humidity in the warmer months, while winter is the drier and
clearer season. This is shown in curve M, fig. 13. The clouds of winter
are low, those of summer are higher. Hence the annual march of
cloudiness on mountains is usually the opposite of that on lowlands.

_Characteristics of the Polar Zones._

_General._--The temperate zones merge into the polar zones at the Arctic
and Antarctic circles, or, if temperature be used as the basis of
classification, at the isotherms of 50 deg. for the warmest month, as
suggested by Supan. The longer or shorter absence of the sun gives the
climate a peculiar character, not found elsewhere.

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