Jökull - 01.12.1993, Blaðsíða 8

For further comparison of temperature conditions,
10-year overlapping means of annual temperature will
be compared between certain Icelandic weather sta-
tions and eastern North-Atlantic weather stations, as
follows:
I. Thorshavn, Bergen, Nordöyan fyr, Bodö, Tromsö,
Vardö; 1901-1990
The variability of 10-year overlapping means of
annual temperature 1901-1990, is rather small for all
the stations mentioned in the heading (Figure 7), as
compared with the Icelandic station, Vestmannaeyjar.
The difference between highest and lowest values of
10-year overlaps is from 0.9° C (Nordöyan fyr) and
1.0° C (Thorshavn), up to 1.2°C-1.3°C at the other
four stations. At the Icelandic stations the same differ-
ence is 1.7°C (Reykjavík), 1.4°C (Teigarhorn), 1.9°C
(Grímsey), and 1.5°C in Vestmannaeyjar. In Vest-
mannaeyjar the difference is largest between the cold
decades in the beginning of the century and the fol-
lowing warmer period.
All the stations shown in Figure 7 show similar
variations. The lowest temperatures occurred in most
of them in 1915/25, and then the temperature started
to increase in Thorshavn, Bergen and Nordöyan fyr.
A rather similar increase began in Bodö, Tromsö and
Vardö after 1910/19. The highest temperatures were
observed in the period 1930/39 on all stations, except
in Vestmannaeyj ar and Thorshavn. After that a gradual
cooling is seen in some of the stations.
At all stations, except Vestmannaeyjar and Thors-
havn, the cold years 1940-1942 are seen, i.e. in the 10-
years means from 1938/47 to 1940/49. A cool period
1947-1952 in Iceland is not seen in other stations. A
decrease in temperature can be seen before the sea ice
period 1965-1971, i.e. inlceland in theperiod 1953/62
to 1956/65, and in Tromsö and Vardö in 1958/67.
Figure 8 shows a map of the mean deviation of
the annual temperature in 1940-1943 from those of
the period 1925-1990. The deviation is positive in
Iceland and S-Greenland but negative at the coast of
W-Norway, and in an area extending north across Jan
Mayen, Svalbard and northwest towards E-Greenland.
The values were calculated as the difference of the
mean values for the two periods, divided by the stan-
Figure 8. Mean deviation of annual temperature be-
tween 1940-1943 and 1925-1990. Calculated with
standard deviation 1925-1990, as a unit. — Meðal-
frávik árshita árin 1940-1943frá árunum 1925-1990.
Staðalfrávik 1925-1990 er notað sem eining.
dard deviation of the period 1925-1990. The reason
for using the standard deviation from 1925-1990 as
a norm is the fact, shown in Figure 4, that standard
deviation is very variable over the region. Using this
standard deviation as a unit, improves the compari-
son between stations in the different parts of the main
region, eliminating those parts of the region, where
temperature changes are caused by local conditions,
rather than general circulation and advection.
We can conclude that the 10-year overlapping
means of annual temperatures during the period 1901-
1990 in the coastal North-Atlantic region do not in
detail show the same characteristics as in Iceland. On
the other hand the variations are similar in Vestmanna-
eyjar and Thorshavn. Weather stations at the coast of
W-Norway show mutually similar variations, except
for a gradually decreasing temperature towards north
(Figure 2).
6 JÖKULL,No. 43, 1993