FTIR
The details of the homogenized FTIR sites can be found here.
Global map of 25 FTIR sites (22 active in ozone) providing ozone data (see NDACC Infrared WG: https://www2.acom.ucar.edu/irwg).
Monthly means of tropospheric ozone column (ground - 150hPa) data in DU for the FTIR sites.