The MAX-DOAS instrument is installed at the premises of the National Observatory of Athens in Penteli (38.05οN, 23.86οE, 527 m a.s.l). It operates in collaboration with the University of Bremen and it is part of the BREDOM network (Bremian DOAS network for atmospheric measurements, Briefly, the instrument comprises a telescope unit, connected to a grating spectrometer equipped with a cooled CCD detector. The telescope unit is mounted on a pan-tilt head in order to be able to point towards any direction in the sky. During routine operation, spectral measurements are performed at various azimuth and elevation angles, providing information on the horizontal and vertical distribution of certain trace gases (NO2, HCHO, CHOCHO, O4). Furthermore, the SCD of oxygen dimer (O4) measured at different elevations can be used as input to the BOREAS retrieval algorithm for the calculation of the aerosols’ vertical distribution. The measurements cover the whole Athens basin.

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The telescope of the MAX-DOAS instrument installed at the premises of the National Observatory of Athens

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MAX-DOAS location and viewing directions.

S direction

MAX-DOAS view towards the urban (S) direction.

Figure 11 1 column fitting

Daily SC density values for NO2 (a, b), HCHO (c, d) and CHOCHO (e, f) as a function of wind direction, for remote (right column) and urban (left column)