| Summary: | From January 2016 until August 2018, an automated Long-Path Differential Optical Absorption Spectroscopy (LP-DOAS) instrument was operated at the German research station Neumayer III (NMIII) in coastal Antarctica to measure trace gas mixing ratios in the boundary layer close to the ground (average altitude above the snow surface: 4m). Two different atmospheric light paths with total lengths of 3100 m and 5900m were available and used depending on the spectral window and visibility. Detectable species were bromine monoxide (BrO), bromine dioxide (OBrO), molecular bromine (Br2), chlorine monoxide (ClO), chlorine dioxide (OClO), iodine monoxide (IO), iodine dioxide (OIO), molecular iodine (I2), sulphur dioxide (SO2), nitrogen dioxide (NO2), nitrous acid (HONO), nitrate (NO3), and ozone (O3). The evaluated data was filtered based on RMS (root mean square) thresholds of optical density residuals of the DOAS fits (see individual data sets for respective values). Detection limits based on a 3-sigma criterion were used and are provided in the data sets for all detectable species. For BrO, ClO, OClO, IO, SO2, and NO2, observations above the respective detection limit were made. For all absorbers the retrieved mixing ratios/concentrations with respective total errors (corresponding to 1-sigma) are provided. The data sets include the observations below the respective detection limit scattered around 0, which due to the spectral analysis with the DOAS approach can include negative values. Significant data points can be selected using the separately provided detection limits (3-sigma criterion - recommended). Alternatively, the total errors can be used. Since total errors and hence detection limits are determined from spectral information, for absorbers not observed at significant levels (OBrO, Br2, OIO, I2, HONO, and NO3), the respective detection limits can serve as an upper limit for an atmospheric presence. The mixing ratios provided here were calculated using meteorological data from Neumayer III station already ...
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