Jökull - 01.12.1991, Page 89

Summary
NEW AVERAGES OF TEMPERATURE
AND PRECIPITATION IN ICELAND,
1961-1990.
The new temperature average 1961-1990 is lower
than the corresponding average of the preceding 30
years (1931-1960) in all months except February
(Fig.l). The extreme northern coastal areas experi-
enced the greatest fall in temperature (about 1°C).
In Fig.2 the year to year temperature variations
can be seen as recorded in Stykkishólmur in the west-
ern part of the country. The period witnessed the end
of the warm period which had reigned in Iceland
since the 1920s and colder climate set in in 1965 con-
currently with increase in drift ice towards the north
and east coast of the country. This cold spell lasted
until 1972 when more variable conditions set in,
never very warm and the cold culminating in 1979
and 1981-1983. From 1984 it became somewhat
warmer, especially in 1987.
Only small changes in the annual precipitation
amounts are evident over most of the country with
the exception of the extreme south and southwest and
the northeast, where the precipitation increased of the
order of 10%. These changes are possibly associated
with the introduction of wind screens on the station
gauges in the late 1940s, the 1950s and the early
1960s. The precipitation increased during the first
half of the year (Fig.3) but decreased in the latter
half. This decrease is especially evident in
September.
Fig. 4 highlights the year-to-year variations in pre-
ciptitation in Stykkishólmur. It can be seen that dur-
ing a greater part of the period the precipitation
remains close to 600 mm pr. year, but rises occasion-
ally to much more, both in 1969 to 1976 and again
from 1988.
In Figs. 5 to 10 the annual variations of different
climatic elements can be seen. Fig. 5 thus shows the
annual variation of temperature in Reykjavík. The
jagged line shows the actual daily means, but on the
smooth one the data are filtered with a normal-type
filter. One should notice the “bump” in the graphs in
late February and early March and the following cold
period. This “bump” is also evident in Fig. 6 (the
temperature in Akureyri).
These late winter peculiarities also show up on the
precipitation figures (7 and 8). They can also been
found in the Reykjavík sunshine graph (Fig. 9) as a
small “bump” in late March corresponding to the
“cold” period when northerly winds with clear and
dry weather seem to be more common than earlier in
March. Another peculiarity can be seen in the
Reykjavík sunshine in June. After the May maximum
and before another maximum in July there is a mini-
mum of sunshine. This is possibly associated with the
snow melting in the central highlands and a resulting
change of the mesoscale circulation over the country.
JÖKULL,No. 41, 1991 87