Airborne in-situ measurements of aerosol particle number size distribution during the HALO-AC3 campaign in March/April 2022

Particle number size distributions (PNSD) in the mobility diameter range of 10 nm to 800 nm were measured using a Mobility Particle Size Spectrometer (MPSS, TROPOS-built; Wiedensohler et al., 2012). During HALO–(AC)³, the MPSS was situated in the aerosol rack (with a compact filter sampler and a miniature CCN counter) onboard Polar 6 and permanently connected to the standard aerosol inlet (Leaitch et al., 2016). Near isokinetic sampling was established for the majority of the flight time by restricting the total aerosol flow through the sampling line (outer diameter 0.75 inch) with the help of a valve. With this, an upper cut-off diameter of roughly 4 µm could be achieved. Each scan of the entire particle size range took approximately 5 min. Data are provided as bin-wise log-normal particle number (dN/dlogDp) for P6 RF01–13. For each of the 40 size bins, the bin's midpoint diameter (Dp) is given. The start and end of each scan is given. Each PNSD was integrated over all Dp to obtain the total particle number concentration (Ntotal). A data flag is given to indicate when sampling was under near-isokinetic conditions. For each scan, the given geolocation is the centroid of P6's flighttrack within the scan's duration. Analogous, the given altitude is the mean altitude of P6 over each scan's duration. All concentration values have been corrected to standard conditions (1013.0 hPa and 273.15 K).