Jökull - 01.12.1971, Blaðsíða 16

feature was most marked in july 1967 when
southerly winds were seldom observed except
during the cold and clear nights. A detailed
picture of the wind field is drawn in Fig. 9. At
first glance we see that gravitational wind dir-
ected down the glacier slope did not dominate
the general windrose. A thorough examination of
the observations did also show that pronounc-
ed local wind systems were rarely observed for
long time. However, they were superimposed
upon the general wind. Only on days with
almost calms, light interrupting, fluttering
wind was the only wind present. This wind
increased only slightly down the glacier. In
daytime the local wind when observed had
variable direction and was often directed up-
hills but in the evening a more direct down-
slope wind was set up. Warming of the air in
contact with the surrounding mountains dur-
ing daytime and strong cooling of the air
above the glacier during the night explains
these features.
A considerable influence of the surrounding
topography is detectable in the windroses. The
mountain Tröllafjall (1471 m) seems to prevent
winds from blowing from N or NE direction.
On the other hand winds frorn NW can follow
the valley. In this connection it should be men-
tioned that Bægisárjökull is in a rain shadow
from Vindheimajökull in NE storms. Further,
the mountain Jökulborgir (1361 m) blocks
winds from S to SE whereas SW winds become
accentuated.
Comparative climatology
Locally generated climate on the glacier is
shown to be dominating only for some few
hours on relatively few days during the summer
and otherwise suppressed by the advective
factors. Mesometeorological studies of winter
TABLE 4.
Comparative climatological and glaciological data from Bægisárjökull and Akureyri.
1 4 JÖKULL 21. ÁR