ACROSS_LISA_PRG_OPC_Sizedistr_PM1_1-Min_L2

The aerosol particle number concentration in different size classes between 0.3 and 20 µm (optical equivalent diameter) was measured at the ground–based PRG urban site during ACROSS by an optical particle counter (OPC) (GRIMM 1.108, Grimm Aerosol Technik GmbH & Co.). The instrument was installed in a dedicated measuring room at the 7th floor of the Lamark B building of Université Paris Cité. Air was taken from a common certified PM1 sampling head located on the roof of the building at about 30 m height above the ground level. A copper tube of 7 mm inner diameter and 10 m length connected the PM1 head to a 4–way stainless steel flow splitter (TSI) located in the measuring room that dispatched the air flow to different instruments. The OPC sampled air from this common line with a flow rate of 1.2 l min–1. Data were acquired continuously at 6-sec time resolution and averaged over 1-min. The time indicated in the datafile is the start time of the 1-min interval. Multiple zero check were performed during the campaign to evaluate possible offset baseline and instrument noise. Data acquired at ambient conditions were reported to Standard Temperature and Pressure conditions (STP, T=273.15K and P=1013.25 mbar). Meteorological data measured at the site were used as reference for ambient T and P. The average estimated error of 29% accounts for uncertainties due to Poisson statistics on total number of particles with optical diameter <1µm. Raw data were controlled manually to check periods when specific conditions prevented to do measurements or affected the quality of the measurements (power cut, zero check, disconnection from the sampling line, disfunctioning). Data in correspondence of these periods are identified as -9999.999 and flagged with a “M” (missing). Valid data are reported with a “O” flag (operation). 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 be provided upon request to the authors and the principal investigators. Measurements for the 13 July-18 July period are not reported because the PM1 head was accidentally disconnected during this period, therefore not ensuring a PM1 sampling. Those data can be provided upon request.