ACROSS_LISA_PRG_SO2_1-Min_L2

The sulfur dioxide (SO2) mixing ratio was measured by a commercial fluorescence UV monitor (AF22E Environnement SA, detection limit 0.4 ppb) at the PRG urban site. Air was taken from the sampling point (located on the roof of the Lamark B building of Paris Cité university at about 30 m height above the ground) to a common glass manifold of 4.3 dm3 volume (located about 10 m below, in the main building) by a teflon tube inlet of 17.5 mm inner diameter and 12 m length. The flow in this main line was fixed at 40 L min-1. The gas phase instruments sampled air from this common manifold. The sulfur dioxide monitor flow rate was set at 0.4 l min–1. Data were acquired continuously at 1-sec time resolution and averaged over 1-minute. The SO2 monitor was calibrated before the ACROSS campaign and the calibration was verified both before and after the campaign. A zero check was performed both before and after the campaign, to evaluate and correct possible offset baseline. The uncertainties given in the data file (5%) account for instrumental (linearity, instrumental drift) and calibration uncertainties. Raw data were controlled manually to remove periods where the manifold was not connected to the sampling line or when specific conditions affected the quality of the data. Invalid data are reported as -9999.999. Valid data are reported with a “O” flag (operation) and invalidated data are reported with a “M” flag (missing). Different periods were affected by rain on the 19–23, 24–27 and 30 June and 4, 19–20 and 22 July. Detailed information on the rainy periods can provided upon request to the principal investigators.