Fróðskaparrit - 01.01.2002, Síða 105

ARKTISKA FJALLAVEÐRIÐ í 2000 Á SORNFELLI
103
Figure 7. Tlie 10 minutes mean
wind speed for year 2000from the
Sornfelli station. The mean annual
wind speed is shown. Only a 41.34
m/s valuefrom the 31 March was
removed from thefigure, andfrom
4 September values above 40 m/s
was filtered out.
7 and 8).
The distribution of the wind direction
data for year 2000 (Fig. 8) shows three
dominating wind directions from the north,
southeast and southwest. The mountain set-
ting of the Sornfelli station causes topo-
graphic effects on the measurements. The
cylinder will produce some airflow distor-
tion. The effect of this has not been investi-
gated. The data, however, demonstrates
that the measuring site is not dominated by
strong turbulence. This would have pro-
duced significant variation in the wind
speed values and a more uniform distribu-
tion of the direction frequencies. This indi-
cates that the Sornfelli station is successful-
ly located for recording the general wind
pattern. Presumably it is suffering from
sonte lee effects, from the slightly higher
located, northern part of the plateau.
The gust winds with a 10 min mean wind
speed above 15 m/s (Fig. 8) show that most
of the storms during 2000 came from
southwest. Storms from the southeast oc-
curred only in January and February, while
northerly storms occurred in March, April,
November and December. The southwest-
erly storms dominated in the spring. Al-
though the summer was generally calm, 32-
sec gusts of up to 28 nt/s did occur 13 June.
The highest gusts recorded during 2000
were 30 m/s for the 32 sec gust 1 January,
and 40.7 m/s for the 2 sec gust 3 January.
Windchill
The mean annual windchill value (U.S. Na-
tional Weather Service, 2001) calculated
based on the corrected air temperature data
at Sornfelli is -7.07°C. This is 8.77°C low-
er than the MAAT value, and shows the sig-
nificant cooling of the mountain due to
wind activity. The relationship between
windchill values and wind direction (Fig.
9) shows that the coldest winds primarily
come from the north and some from the
southwest, whereas winds in the sector
from east to southwest predominantly bring
winds with windchill values frorn +5°C to