Examining the effect of horizontal gradients in trace gas distributions during the intercomparison campaign CINDI-3

The third Cabauw intercomparison of DOAS-type instruments (CINDI-3) campaign took place at the CESAR measurement site near Cabauw, Netherlands in June 2024. Stationary DOAS instruments were supported by mobile platforms: cars, a bike and an airplane mapped the horizontal distribution of trace gases in the regions around Rotterdam and Cabauw. In this work, we combine the information gained from all mobile platforms to obtain the horizontal distribution of nitrogen dioxide (NO₂). During the campaign additional MAX-DOAS instruments were set up along the main viewing azimuth direction to investigate the retrieval of horizontal gradients from MAX-DOAS instruments using a tomographic approach. Here, we present NO₂ maps obtained from the mobile measurements, the differences between the stationary instruments and the resulting implications for the tomographic approach.