The total ozone and ozone deviation maps are based on ground-based measurements by Brewer spectrophotometers carried out by the Science and Technology Branch of Environment Canada. Total ozone values are given in Dobson Units. The numbers represent observations taken from ground stations situated at the bottom left corner of the number. The numbers marked by “*” symbol are obtained using indirect method of measurements and are less reliable. Maps of deviations represent total ozone deviations from the 1978-1988 level estimated using TOMS data.
These maps are normally updated hourly between 1400 and 2300 UTC. However, this near-real-time system is automated, so if a system problem occurs outside of regular working hours, it will not be fixed until the following work day.
WARNING: The data are processed in near real-time, have not been fully validated, and are preliminary.