The Canadian Brewer Spectrophotometer Network (CBSN) monitors the total thickness of the ozone layer (known as total column ozone) and ultraviolet (UV) radiation at selected monitoring locations across Canada. The objectives of the network are to provide long-term stratospheric ozone data for periodic assessment of the state of ozone layer; use the data for validating satellite ozone data (total ozone and UV); and provide long-term data of spectral UV for biological effect studies (e.g., vitamin D production), ozone data for Environment Canada UV index forecasts, and data for studying current and emerging issues such as climate change (stratosphere).