SupplementThe first part of the supplement presents a modified version of Fig. 4. In contrast to the original figure, in Fig. S1 the error bars are shown for the retrievals assuming a box-profile (shape parameter = 1).The second part of the supplement (Figs. S2 -S11) presents the individual graphs of the correlation analyses between the MAX-DOAS results versus independent measurements as well as between MAX-DOAS results of the different telescopes.In the third part of the supplement, the results of the normalised radiance and the normalised O 4 dAMF α (Fig. S12) are shown for the whole campaign.The fourth part of the supplement (Fig. S13) presents results for individual days (individual elevation sequences) are shown. For comparison, AOD from the AERONET station at Ispra, NO 2 and HCHO mixing ratios from the long path DOAS instrument, and HCHO mixing ratios from the Hantzsch instrument are also included.