The Botany of Iceland - 01.12.1945, Side 28

370
STEINDÓR STEINDÓRSSON
3. CLIMATIC REMARKS
These remarks on the climate of the highland must necessarily be
very sporadic, since no systematic investigations are available, on which
they might be based. Most useful in this respect are the meteorological
observations made at the most elevated stations, notably M ö ð r u-
d a 1 u r and Grímsstaðir in the northern part of the country.
As no corresponding observations are available from other parts of the
country, every comparison of the climates of the different regions must
be largely conjectural.
A. Temperature.
As regards the temperature, registrations from Möðrudalur and
Grímsstaðir must be used as a basis. Since Möðrudalur is situated more
than 400 m above the sea, right up on the open plateau the innermost
part of which is Brúaröræfi, the climate of these two places is bound
to show close agreement. For a further comparison it will be very useful
to employ the observations made at Grímsstaðir situated 385 m above
the sea. The subjoined tables give a fairiy good idea of the temperature
conditions in the highland north of Vatnajökull, although Möðrudalur
lies some 150 to 200 m lower than the most elevated stations. According
toThoroddsen (1914, p. 280) the mean temperatureofthecoldest
day and night in Möðrudalur was —2g°C, but according to “Veðráttan”
this temperature for the period 1925-1934 is —24-4°C, whereas the
mean temperature of the warmest day and night of the same period
is 22-9°C. This shows that we are here concerned with fairly large
fluctuations of the temperature, both annual fluctuations and, what is
perhaps of still greater importance to the vegetation, diurnal fluctua-
tions. It is not uncommon for the temperature on clear days in summer
to vary from i5°-20° in the afternoon to some degree of frost in the
night. Altogether the temperature is very unstable and incalculable in
these regions. Lamprecht, who travelled in the regions west of
Jökulsá á Fjöllum in July 1927, gives the following description of the
weather: “Kaum hatte bei unserem Ritt ein Sandsturm bei glutheissem
Wetter aufgehört als ... erst ein Regen dann ein Schneesturm empfing ...
Die Náchte waren nach warmen Tagen z. T. eiskalt so dass Wasser auf
den kleinen Taupfiitzen mit einer dúnner Eisschicht bedeckt war, z. T.
war es so warm dass ich z. B. in Herðubreiðarlindir meine náchtlichen
Pferdewáchte in der leichten Tageskleidung zubringen konnte”
(Lamprecht 1930, p. 118).