Average (1994–2012) relative differences (%) of trajectory-mapped MOZAIC/IAGOS profile data minus trajectory-mapped ozonesonde data (Osman et al., paper in preparation). Variations with latitude in the left-hand plot are likely due to differences in sonde type and preparation, which may cause biases of several percent. When averaged over latitude, sonde measurements are about 5 ± 1% higher, in the lower troposphere, and 8 ± 1% higher in the upper troposphere, consistent with the average biases found from UV-referenced sonde intercomparison studies (Section 4.3). DOI: https://doi.org/10.1525/elementa.376.f20