Maps of annual mean TCO (DU) from five satellite products and ozonesondes (TOST). Annual mean tropospheric column ozone (TCO) in Dobson unit (DU) as measured by TOST (top left), OMI/MLS (top right), OMI-SAO (middle left), OMI-RAL (middle right), IASI-FORLI (bottom left) and IASI-SOFRID (bottom right). The data are averaged over the period January 2010 through December 2014 and reported at 5° × 5° horizontal resolution, except for TOST, which covers the period 2008–2012. DOI: https://doi.org/10.1525/elementa.291.f10