Jökull - 01.12.1991, Síða 6

Table 1
Monthly and annual mean temperature 1901-1990, °C
Tafla 1
Mánaðar- og ársmeðalhiti 1901-1990, °C
Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Year
Reykjavík -0.4 0.1 0.9 3.0 6.5 9.4 11.1 10.6 8.0 4.6 1.6 0.3 4.6
Stykkishólmur -1.2 -1.0 -0.5 1.4 5.0 8.3 10.1 9.6 7.3 4.0 1.2 -0.4 3.7
Grímsey -1.2 -1.2 -1.3 -0.1 2.7 5.9 7.7 7.6 5.8 3.2 0.8 -0.5 2.5
Akureyri -2.0 -1.7 -1.0 1.4 5.5 9.1 10.7 9.8 7.0 3.0 0.0 -1.5 3.4
Teigarhorn 0.0 0.3 0.7 2.0 4.4 7.1 8.7 8.7 7.2 4.5 1.7 0.5 3.8
Vestmannaeyjar 1.3 1.5 1.9 3.2 5.7 8.1 9.8 9.6 7.8 5.2 2.8 1.8 4.9
Stórinúpur/Hœll -1.7 -1.3 -0.3 1.9 5.9 9.2 11.1 10.2 7.1 3.5 0.4 -1.1 3.8
year. It was calculated for the two periods 1901-1985
and 1941-1985. The difference between the two
periods was found to be insignificant at the 7 weath-
er stations in operation since 1901.
There is a distinct annual variation of the standard
deviation in Iceland. Fig.3 shows monthly averages of
the standard deviation for 7 stations 1901-1985 and
for 32 stations 1941-1985. The highest monthly aver-
ages are found for the months January-March, usually
highest in March in northern and eastern Iceland and
in the extensive lowlands of southern Iceland. In
other areas the January values are equally high or
even a little higher. The lowest averages are found for
the months June-August, almost equal for all of them.
The large difference in standard deviation between
winter and summer months is not surprising. In win-
ter low pressure systems are frequent and deep, and
strong advections of warm or cold air masses can be
expected.
It seems reasonable to divide the year into seasons
on the basis of standard deviation as seen in Fig.3. In
later chapters January-Marcli will be looked upon as
winter, April-May as spring, June-August as summer
and September-December as autumn. When compar-
ing temperature for different seasons it must be born
in mind that their length is different, 2^1 months. It is
advantageous however that the adverse seasons, win-
ter and summer, both include 3 months.
The variation of the standard deviation between
different parts of the country was studied, using the
calculated values for the 32 selected weather stations
for the period 1941-1985.
Fig.4 shows the standard deviation of annual tem-
perature. The values, of the order 0.55°-0.90°C, are
for most stations lower than in the months June-
August which are the months of minimum standard
deviation. The lowest values are found at the south
coast and then increasing towards north. In northern
Iceland the values are generally >0.8°C with a maxi-
mum in the interior of the northeastern part.
4 JÖKULL, No. 41, 1991