Monitoring of the atmospheric ozone layer and natural ultraviolet radiation. Annual report 2011.

This is an annual report describing the activities and main results of the monitoring programme \'Monitoring of the atmospheric ozone layer and natural ultraviolet radiation\' for 2011. 2011 was a year with generally low ozone values above Norway. A clear decrease in the ozone layer above Norway during the period 1979-1997 stopped after 1998 and the ozone layer above Norway seems now to have stabilized.