|Daily total ozone values of Sodankylš expressed in Dobson Units (DU) (yellow dots) are mainly Brewer spectrophotometer data.The data gap during the winter when the sun is not high enough for Brewer is filled by
mainly data from SAOZ (Systeme d'Analyse par Observation Zenithale) but some points are obtained from Brewer focused moon observations.
The direct sun measurements are used ranking first. When this is not possible due to clouds measurements are taken from zenith sky.
Focused sun method is used during
the beginning and end of winter.
The black line presents the long time mean of TOMS satellite instrument observations for comparison. Also these data are missing for the mid-winter months (dotted line).
Latest total ozone map of the Northern Hemisphere is available at Environment Canada.