Jökull - 01.12.1988, Síða 64

Fig. 1. Locations in southwestem Iceland where
regular precipitation measurements have been made.
Unshadowed signs show places with measurements
for only one year or stations only in operation dur-
ing the summer. Broken lines are 300 m contours.
Mynd 1. Staðir suðvestanlands þar sem reglulegar
úrkomumœlingar hafa farið fram í lengri eða
skemmri tíma. Oskyggð merki sýna 6 staði þar sem
aðeins var um mælingar í eitt ár að ræða og tvo þar
sem aðeins er mælt að sumarlagi. Brotnar línur eru
300 m hæðarlínur.
on the average be approximately 25% too low. This
figure is highly dependent on wind velocity and a
higher value is to be expected for snow. Unfor-
tunately no reliable corrections are available. This
fact must be considered when interpreting the pre-
cipitation measurements.
MONTHLY AND ANNUAL PRECIPITATION
Monthly and annual average precipitation values
for the period 1931-1960 are primarily based on 42
stations with at least 9 years measuring period and
in addition 12 stations with shorter periods.
The question may arise, how different average
precipitation values for the normal period 1931-
1960 are from average precipitation values for the
last two or three decades. In Fig. 2 average values
for the periods 1931-1960 and 1961-1980 are com-
pared for 6 measuring stations in southwestem Ice-
land (Reykjavík, Hólmar í Landeyjum, Hæll, Eyrar-
bakki, Þingvellir, Keflavíkurflugvöllur). The differ-
Fig. 2. Average annual precipitation for the periods
1931-1960 and 1961-1980 at Reykjavík, Hólmar,
Hæll, Eyrarbakki, Þingvellir and Keflavík airport.
Mynd2. Meðalársúrkoma 1931-1960 og 1961-1980
í Reykjavík, á Hólmum í Landeyjum, Hœli, Eyrar-
bakka, Þingvöllum og Kefiavíkurflugvelli.
Fig. 3. Average monthly precipitation 1931-1960 at
Eyrarbakki and Reykjavík.
Mynd3. Meðalúrkoma 1931-1960 á Eyrarbakka og
í Reykjavík.
ence is small indeed, from -3% to 6%. It should be
noted, that rain gauges were used without wind shi-
elds a large part of the former period, and the values
may therefore be somewhat lower for that reason.
Autumn and early winter represent the seasons of
greatest precipitation in southwestem Iceland, and
as a matter of fact in most of the country. Fig. 3
shows annual variation of monthly precipitation for
62 JÖKULL, No. 38, 1988