The Botany of Iceland - 01.12.1930, Qupperneq 17

STUDIES ON THE VEGETATION OF ICELAND
7
fortunately there are no records from the highlands. The number
is probably considerably higher here.
Precipitation. The precipitation in suinmer is principally rain,
in winter principally snow. The annual precipitation is greatest to
the south and east, decreasing towards the west and being compa-
ratively small in the north.
In the Vestmannaeyjar the annual precipitation is 1319 mm. (see
table 1), distributed over 207 days, in East Iceland it is 1117 mm.,
distributed over 146 days, in West Iceland, Stykkishólinur, the amount
of precipitation is already considerably lower, 662 mm. distributed
over 117 days. From the highland tracts we have unfortunately no
investigations on the amount of precipitation for the whole year, so
it is impossible to draw any comparison with the coastal stations.
The number of days with precipitation for Möðrudalur is 153, thus
somewhat higher than for Grímsey, corresponding fairlj' well with
East Iceland. It may, however, be taken for granted that the amount
of precipitation is not nearly as great in the highland tracts as at
the coast. Observations from some of the sumrner months at a
highland station, Grímsstaðir, about 385 m above the sea, in the
vicinity of Möðrudalur, show an average monthly value for the five
months Maj'—September of 26.8 mm, while the average monthlj'
amount of precipitation for Grímsey for the íive months is 31.4 mm.
The amount of precipitation and the number of days with pre-
cipitation are highest in the autumn and winter months, lowest in
spring and summer. This applies especially to the regions to the
south of glaciers.
In winter the precipitation occurs principally in the form of
snow, though with a difference in the diííerent parts of the country.
Table 1 shows the number of days with snow for the different
stations where this has been investigated. In the highland tracts
and the north country snow predominates, in the south there are
comparatively few days with snow; while snow is rare here in the
summer, it is more frequent in the north. In the highland tracts
snow in summer is even the rule. At Möðrudalur the average monthly
number of days with snow in summer is 2—4.
Unfortunately there are no observations on the depth and du-
ration of the snow-covering in the various regions of Iceland. As
to tlie depth of the snow-covering Thoroddsen states that it varies
mucli with the situation and the altitude above the sea, and from
one year to another. As to its duration lie states that the snow