Abstract
Abstract. We first validate the performance of the Portable Optical Particle
Spectrometer (POPS), a small light-weight and high sensitivity optical
particle counter, against a reference scanning mobility particle sizer
(SMPS) for a month-long deployment in an environment dominated by biomass
burning aerosols. Subsequently, we examine any biases introduced by
operating the POPS on a quadcopter drone, a DJI Matrice 200 V2. We report
the root mean square difference (RMSD) and mean absolute difference (MAD) in
particle number concentrations (PNCs) when mounted on the UAV and operating
on the ground and when hovering at 10 m. When wind speeds are low (less than 2.6 m s −1 ), we find only modest differences in the RMSDs and MADs of 5 % and
3 % when operating at 10 m altitude. When wind speeds are between 2.6 and 7.7 m s −1 the RMSDs and MADs increase to 26.2 % and 19.1 %, respectively,
when operating at 10 m altitude. No statistical difference in PNCs was
detected when operating on the UAV in either ascent or descent. We also find
size distributions of aerosols in the accumulation mode (defined by
diameter, d , where 0.1 ≤ d ≤ 1 µ m) are relatively consistent
between measurements at the surface and measurements at 10 m altitude, while
differences in the coarse mode (here defined by d > 1 µ m)
are universally larger. Our results suggest that the impact of the UAV
rotors on the POPS PNCs are small at low wind speeds, but when operating
under a higher wind speed of up to 7.6 m s −1 , larger discrepancies occur. In
addition, it appears that the POPS measures sub-micron aerosol particles
more accurately than super-micron aerosol particles when airborne on the
UAV. These measurements lay the foundations for determining the magnitude of
potential errors that might be introduced into measured aerosol particle
size distributions and concentrations owing to the turbulence created by the
rotors on the UAV.
