Spatial and temporal distributions of NO2 and aerosols over the urban environment of Vienna during the VINDOBONA project (2017-2019)

Within the scope of the VINDOBONA (VIenna horizontal aNd vertical Distribution OBservations Of Nitrogen dioxide and Aerosols) project, spectral UV/vis measurements at selected viewing directions are performed with three MAX-DOAS (Multi AXis Differential Optical Absorption Spectroscopy) instruments, which are located in the northeast, northwest, and south of the city center of Vienna, Austria. The selection of viewing directions of the three instruments was chosen in a way to provide data for the retrieval of horizontal and vertical trace gas and aerosol distributions, in particular over the urban core.

In the present work, the profile retrieval algorithm BOREAS (Bremen Optimal estimation REtrieval for Aerosols and trace gaseS) is used to retrieve aerosol and NO2 vertical profiles as well as accompanying parameters aerosol optical depth, tropospheric NO2 vertical columns (TVC NO2), and near-surface NO2 on days with cloudless conditions. The retrieval results are compared with co-located ceilometer, sun photometer, surface air quality, and TVC NO2 measurements, with the latter being obtained by applying the geometrical approximation and converting zenith-sky NO2 measurements.