NO2 mixing ratios at 10s time resolution from CE-DOAS measurements during M91.The open-path CE-DOAS instrument consisted mainly of an optical resonator with effective light path lengths of up to 5km and uses a temperature stabilized LED and Avantes spectrometer in the blue spectral range.The data analysis was done according to Platt et al 2009 (doi:10.5194/amt-2-713-2009) using the NO2 cross-section by Vandaele et al 1998 (doi:10.1016/S0022-4073(97)00168-4), O4 cross-section by Thalman et al 2013 (doi:10.1039/c3cp50968k) and the HITRAN2012 (Rothman et al 2013, doi:10.1016/j.jqsrt.2013.07.002) water vapour absorption cross-section covering a spectral range from 425-460nm. An IO absorption cross-section by Spietz et al 2005 (doi:10.1016/j.jphotochem.2005.08.023) had to be included, while significant glyoxal absorption was not found and thus not considered in the final spectral analysis.The spectral data can be found on the measurement data server at the Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany