Comparison of aerosol measurement systems during the 2016 airborne ARISTO campaign

Several different types of measurements of particle size and concentration were compared during the 2016 Airborne Research Instrumentation Testing Opportunity (ARISTO) campaign. The scanning mobility particle sizer (SMPS) measured number-size distributions for mobility diameters between ∼20–350 and ∼8–110 nm, depending on the mobility analyzer chosen. Also included were two stand-alone condensation particle counters (CPC) for determining size-integrated particle concentrations. A wing-mounted and a rack-mounted Ultra-High Sensitivity Aerosol Spectrometer (UHSAS) were used to measure size distributions between 60 and 1000 nm. Lastly, two different sampling inlets were used to investigate performance and observe any systematic biases. Most sampling occurred during cloud-free summer conditions in the western United States. Number concentrations from the two CPCs typically agreed within 12% once the flows in the ultrafine particle counter were corrected as a function of pressure. As expected, the size-integrated number concentrations from the SMPS and UHSAS were generally less than those of the CPCs, as the former cover only part of the total range of particle sizes measured by the CPCs. Integrated number concentrations from the wing-mounted and rack-mounted UHSAS generally agreed within 20% for all diameter ranges analyzed. The overlap region between the SMPS and the UHSAS showed reasonable agreement of ±20%. Some of the uncertainty regarding these measurement comparisons originates from a variety of factors, including sampling frequency, particle refractive index, differences between physical and mobility diameters, and counting efficiency uncertainties in the UHSAS optical cavity, especially for the smallest diameters (60–100 nm).

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