Jökull - 01.12.1991, Blaðsíða 5

J FMAMJJASOND
Fig.2 : Mean annual range of temperature 1901-1990
for Reykjavík, Grímsey, Akureyri, Teigarhom, Vest-
mannaeyjar and Stórinúpur/Hæll.
Mynd 2 : Árlegur gangur hitans 1901-1990 í
Reykjavík, Grímsey, Akureyri, Teigarhorni,
Vestmannaeyjum og Stóranúpi/Hœli.
tm - 1/9 (4t6 + 2t13 + 3t16)
For the period April 1922-August 1927 it is esti-
mated that the formula in use for Akureyri was:
tm - 1/5 (2t6 +18 + t12 +117)
In 1956 the following formulae were introduced
for most stations:
t-m = 1/2 (h) + l2l) + C1
tm = 1/2 (t9 + t22) + C2
tm = 1/6 (5t9 + t18) + C3
The hours of observation are here shown in GMT.
The coefficients cb c2 and c3 aie corrections. Gradually
the observation time 22h GMT was changed to 21
GMT, so the first of the three formulae is now in use
for most stations not having 3-hourly observations.
During the period 1949-1959 wall-screens for
temperature measurements were substituted by freely
exposed screens. Unfortunately comparing measure-
ments between the two types of screens, making cor-
rections possible, were only made at a few stations.
MEAN TEMPERATURE 1901-1990
As already mentioned 7 of the 32 selected weather
stations were already in continuous operation in the
year 1901. These are: Reykjavík, Stykkishólmur,
Grímsey, Akureyri, Teigarhorn, Vestmannaeyjar and
Stórinúpur/Hœll. Stykkishólmur is Iceland’s oldest
weather station providing continuous records of tem-
perature since 1845. The next one, Teigarhorn, start-
ed in 1873, at that time being called Berufjörður.
In Table 1 mean monthly and annual temperature
for the period 1901-1990 is seen for the above men-
tioned 7 weather stations and Fig.2 shows the annual
range of temperature for six of them. Both the table
and the figure show some characteristics of tempera-
ture in Iceland. There is a considerable difference in
the annual range between coastal and inland stations.
Maritime influences seem to be more distinct at the
east coast (Teigarhorn) than at the west coast (Reykja-
vík, Stykkishólmur). At Grímsey, an island crossed by
the Arctic Circle just to the north of the country,
March is the coldest month of the year although the
difference between January, February and March is
very small. At the north and east coast (Grímsey,
Teigarhom) there is a very slight difference between
the mean temperature in July and August.
Seven weather stations are insufficient to give a
detailed description of the temperature conditions in
Iceland. To do so a 50-year period, 1936- 1985, will
be used in a later chapter.
STANDARD DEVIATION - SEASONS
Standard deviation is a good measure of the variabil-
ity of monthly and annual temperature from year to
JOKULL, No. 41, 1991
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