Náttúrufræðingurinn - 1956, Síða 14

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NÁTTÚRUFRÆÐINGURINN
4, 5 and 6 (2. mynd etc.) supports the validity of these radiation measure-
ments. — Grapli 2. shows the parallelism between the average o£ the sun’s
course (between sunrise and sunset), liours of sunshine and the total radia-
tion. — Graph 3. shows an approximate inverse proportionality between the
average atmospheric humidity and tlie daily mean values of the monthly
radiation. — Graph 4. sliows liow the average length between sunrise and sunset
and monthly precipitation vary inversely during the first half of year 1955,
and a proportionality during the second half of the year, i. e. less precipitation
during the late winter months and early spring. It is evident from graph
5, which shows the average atmospheric humidity and average monthly
intensity o£ the radiation, that the radiation increases as the humidity de-
creases. From graph 6. showing average temperature, average atmospheric
pressure as well as total monthly radiation may be seen, tliat there is no
necessary relationship between total radiation and temperature — this is most
obvious during the months April—October 1955. It is also evident, that total
radiation and atmospheric pressure are not necessary related.
Table II shows a comparison of the results with published data from
Fairbanks and Potsdam. Here one realizes the much greater radiation during
the summer months at Fairbanks than in Reykjavík and also the small diffe-
rence between radiation in Reykjavík and Potsdam.
Table III shows a comparison with published data front Helsinki. The
most outstanding feature is, that Reykjavík receives only 41000 cal/cm2
during the year where as it is in Helsinki 74000—80000 cal/cm2 a year. Also
during the growing period the radiation received in Reykjavík is only about
28000 cal/cm2 but in Ilelsinki it is almost 56000 cal/cm2.
However the annual variations in Reykjavík are not yet known, but as a
result of these unexpected low values it seems possible, that variations in
radiation may play a more important role for agriculture as well as other
conditions of life in Reykjavík and SW-Iceland than in some other places
of the northern hemisphere.